Character association and selection of breeding line based on morphophysiological characteristics and tensile strength in Hibiscus cannabinus L.

Mohamad Ismail, F. N., Abdul Hamid, H., Mohamed, J., Abdu, A., Samdin, Z., and Mohd Razali, S. (2020). "Character association and selection of breeding line based on morphophysiological characteristics and tensile strength in Hibiscus cannabinus L.," BioRes. 15(4), 8883-8908.

Abstract

This study aimed to access different desirable characteristics of nine Hibiscus cannabinus L. accessions based on morphophysiological characteristics and fiber tensile strength for an effective selection of H. cannabinus plant improvement. Four China accessions (FH952, T15, T17, and T19), four Bangladesh accessions (HC2, HC95, V4202, and V4383), and V36 (control) accession were examined in a four-month cultivation period. The experimental design was arranged using randomized complete block design with three replications. Stem diameter was found to be significantly related (p ≤ 0.05) with all morphological and yield characteristics except for leaf dry weight and growth efficiency. Bigger stem diameter was an indicator of fiber yield in attempts to apply crossing and selection to improve performance. Photosynthesis rate also was found to be significantly related (p ≤ 0.05) with stomatal conductance, transpiration rate, instantaneous water use efficiency, and carboxylation efficiency. High photosynthesis rate could be an indicator to interpret the pattern of genetic variation of plant assimilation rate and its relation with environmental and agronomic factors. The fiber tensile modulus, however, was found to be inversely correlated with fiber diameter. The present study suggests the selection of control, V4383, HC2, and FH952 accessions for a breeding line as they possess high fiber yield, fiber strength, and photosynthetic efficiency.

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Character Association and Selection of Breeding Line Based on Morphophysiological Characteristics and Tensile Strength in Hibiscus cannabinus L.

Fatin-N. M-Ismail,*^,a Hazandy A-Hamid,^a,b Johar Mohamed,^a Arifin Abdu,^bZaiton Samdin,^a,c and Sheriza M-Razali ^a

Keywords: Kenaf; Fiber; Morphology; Physiology; Tensile strength

Contact information: a: Laboratory of Bioresource Management, Institute of Tropical Forestry and Forest Products, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia; b: Department of Forestry Science and Biodiversity, Faculty of Forestry and Environment, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia; c: Department of Economy, Faculty of Economy and Management, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia;

* Corresponding author: fatinnorliyana22@gmail.com

INTRODUCTION

Kenaf, which is scientifically named Hibiscus cannabinus L., is an agro-based lignocellulosic that is grown specifically for its fiber. Various annual crops such as cotton (Gossypium hirsutum), hemp (Cannabis sativa), jute (Corchorus capsularis), kapok (Ceiba petandra), and coconut (Cocos nucifera) are known to produce natural fibers. H. cannabinus however has advantages of harvesting operation and cost-effectiveness because the fiber is obtained from its vegetative plant part (stem) instead of reproductive plant part, and the fiber yields are greater than those of the above mentioned crops (Tahery 2011). Being comprised of 65% woody inner core and 35% fibrous outer bast makes H. cannabinus a hard fiber plant with an excellent source of cellulose fiber (Tahir et al. 2015). The yield and fiber quality such as fiber diameter, fiber length, and fiber strength, however, differ greatly among cultivars; these traits can be affected by genetic inheritance and manipulation, environmental factors, and also by their interactions (H’ng et al. 2009; Abdul Khalil and Suraya 2011; Faruq et al. 2013).

The yield, for example, is firmly related to plant growth performance and their physiological attribute such as photosynthesis rate (Evans 2013). The products of photosynthesis are utilized in the development and differentiation of new cells as well as supporting the existing tissue of the plant. The greater photosynthetic rate and high specific activities of RuBP carboxylase possess higher biomass production as well as fiber yield. The superior photosynthetic rates and high biomass yield are also related to the amount and the efficiency of carboxylation capacities in leaf that considered as regulating the photosynthetic capacity in C3 plants (Acquaah 2007). However, Reddy and Das (1986) suggest that losses of available energy to support photosynthesis are due to physical properties of leaves and more fundamental energy considerations for successful conversion and storage of sunlight as chemical energy in the photosynthetic process. To assess the efficiency of the photosynthesis process in a plant, knowledge of total plant biomass production must be acquired. Morphological and physiological attributes also help to better understand the plant plasticity and adaptive mechanism (Abdul-Hamid et al. 2009).

Furthermore, fiber strength and micronaire are associated with cellulose deposition within fiber and the developmental process, which are related to fiber secondary wall characteristics (Wang et al. 2009). The manipulation of the relationship between the photosynthetic assimilate source and the reproductive sink also would affect fiber strength and micronaire formation (Chen et al. 2017). Lokhande and Reddy (2014) reported that a decrease in leaf water potential resulted in decreases in fiber properties such as fiber length, strength, and uniformity, but an increase in fiber micronaire. However, the alternation in the available assimilate supply to the developing bolls affects fiber quality less directly than the yield (Pettigrew 2001). Therefore, better understanding of the responses of leaf photosynthesis is crucial in order to enhance the yield and improve fiber quality (Long et al. 2006; Khan et al. 2019). In this study, the authors investigated morphophysiological quantitative characteristics and tensile strength of nine H. cannabinus accessions as a breeding line selection for a future H. cannabinus breeding program.

EXPERIMENTAL

Materials

Nine H. cannabinus accessions were selected in this study from three different origins (Table 1). The accessions were selected based on the availability in the previous study of the accessions in Malaysia. Amongst them, V36 is one of the main accessions in seed and fiber production in Malaysia; therefore it was selected as the control accession in present study to ensure better selection of accessions. Approximately 100 g of seeds with three replications (100 seeds x 3 replications: 300 seeds) for each accession were prepared for seed moisture content (oven-dry method), and 100 seeds with three replications (100 seeds x 3 replications x 2 methods: 600 seeds) were used for germination tests for each accession as recommended by the International Standards for Genebanks (Rao et al. 2006). The top of paper method and between paper method (ISTA 2005) were used in the presence of basic requirements for seed germination such as water, oxygen, light, and suitable temperature.

The seeds for field trials were soaked (pre-treatment) in a 400 mL beaker (Pyrex Iwaki TE-32 Asahi Glass; Pt. Iwaki Glass, Sumedang, Indonesia) filled with distilled water for 24 h before being sown at the experimental site to improve germination and seedling growth (Donovan 2001). The evaluation of seedlings was performed according to specific criteria listed by International Seed Testing Association (ISTA) (2005) and Association of Official Seed Analysts (AOSA) (2016). The accession names, origin, seed moisture content, and seed germination results are tabulated in Table 1.

Table 1. Accession Name, Origin, Seed Moisture Content, and Seed Germination of Nine Selected H. cannabinus Accessions

Study Site and Experimental Design

The study site was established at University Agricultural Park, Universiti Putra Malaysia, Serdang, Selangor, Malaysia (2° 58’ N latitude, 101° 39’ E longitude), with an area of 26 m × 10 m. It receives up to 2140 mm mean annual precipitation, 26 °C mean annual temperature, and 5 h to 8 h average radiance. The study was conducted from July 2017 to October 2017.

The experiment was arranged using a randomized complete block design. The randomization was assigned using a table of random numbers (Gomez and Gomez 1984) with three replications of planting block. Each block consisted of nine accessions with 10 plants for each accession. The individual plants were arranged with 30 cm planting distance, with 1 m between subblocks and 2 m between blocks. The total number of plants were 270 (10 plants x 9 accessions x 3 replications). Approximately 5 g of Nitrophoska standard formulation fertilizer (15:15:15) (EuroChem, Zug, Switzerland) was supplied manually for each plant on a monthly basis. The insecticide (Kencis with 5.5% Emulsifiable Concentration (EC) of cypermethrin active ingredient; Kenso Corporation, Petaling Jaya, Malaysia) in mixture of 13 L of water and 0.013 L of insecticide (0.01% concentration) was periodically applied twice per month to keep the plants healthy as guided by the Pesticide Control Division of the Department of Agricultural Malaysia.

Soil Sample Analysis

The soil samples were taken from the depth of 0 to 15 cm and 15 to 30 cm using the zig-zag pattern for the whole (Ackerson 2018) experimental site. The samples were air-dried for one week, ground, and sieved through a 2 mm pore size sieve. Soil particle-size analysis was conducted by the relative quantities of sand, silt, and clay using pipette method (Gee and Bauder 1986). The time and depth of the sampling are deduced using Stoke’s Law (Stokes 1849). Soil classification were then classified according to scheme developed by USDA (United States Department of Agriculture) in which the soil particles and their sizes ranges are: sand (50 to 2000 µm), silt (2 to 5 µm), and clay (< 2 µm).

Soil texture was determined by using the texture software by Teh and Rashid (2003). Soil pH was measured in soil/ water (1: 2.5) suspension. Total carbon and total nitrogen were measured by CNS analyzer machine (model: LECO TruMac CNS Analyzer). The available phosphorus (P) was determined by Bray-II method as described by Kuo (1996). The exchangeable potassium (K), calcium (Ca), and magnesium (Mg) were determined using an autoanalyzer (QuikChem, Series 8000, Lachat Instruments Inc., USA), and the concentrations of calcium (Ca) and magnesium (Mg) were also determined by atomic absorption spectrophotometer (Perkin-Elmer 5100 PC) (Hazma et al. 2015). The initial physical and chemical properties of the soil are presented in Table 2.

Table 2. Initial Soil Physical and Chemical Properties at the Experimental Site

Note: % of N = 10,000 µg/g

Methods

Morphophysiological characteristics

The data on quantitative morphological, physiological, and yield characteristics were assessed according to the Sustainable Projects Development Group of UK and the literature (Pace et al. 1998; Ahmad et al. 2001) in replicates of 30 specimens for each accession. Both quantitative characteristics (morphological and physiological) were measured monthly using specific measuring equipment, and yield characteristics were recorded after harvest (Table 3).

Laboratory sample preparation

Alkaline treatment involved immersing the fibers in an alkaline solution for a period of time. It was believed that alkaline-treated fibers provide higher tensile modulus than the untreated fibers (Li et al. 2007). In the present study, sodium hydroxide (NaOH) and sodium sulfite, anhydrous (Na₂SO₃) were used to remove surface impurities (lignin, wax, and oil covering the external surface of fiber cell wall), while acetic acid (CH₃COOH) was used in retaining a high index of crystallinity (Mohanty et al. 2000) and giving the whitest color of fiber (Hurren et al. 2002).

Table 3. Description of the Measured Quantitative Characteristics of Nine Selected H. cannabinus Accessions

For the retting process, three replications of plant samples for each accession were prepared by cutting the lower part of H. cannabinus stem approximately 10 cm above the ground. The sample was peeled manually to separate the bast fiber and core fiber. The bast fiber was cut into 15 cm of length, in weight of 30 g per sample (Amel et al. 2013).

The aqueous solution for the retting process was prepared by mixing 7% NaOH and 0.5% Na₂SO₃ solution.The mixed solution was then stirred using a magnetic stirrer (IKA Magnetic Stirrers RH 2 Basic; IKA Works (Asia) Sdn. Bhd., Selangor, Malaysia). The bast fiber was then immersed into the aqueous solution using a narrow mouth conical flask (Pyrex No. 4980 250 mL Erlenmeyer Flask; Corning Inc., New York, USA). It was then soaked in a water bath (Nickel Electro NE4-22T; Thermo Fisher Scientific Inc., Goteborg, Sweden) for 60 min at 100°C. After the retting process, the sample was neutralized by removing the sample from the aqueous solution, placing filter paper in a glass conical funnel, and rinsing with 2% CH₃COOH (Ramaswamy and Boyd 1994). The unattached lignin, wax, and color were then removed by two dunks in hot plain water at 70 °C. The fiber was then submerged under plain water and dunked 10 times before it was air-dried for two weeks (Hurren et al. 2002). The sample was then used for fiber diameter measurement and tensile strength testing.

Fiber diameter determination

SEM imaging was conducted at the Laboratory of Biopolymer and Derivatives, Institute of Tropical Forestry and Forest Products (INTROP), Universiti Putra Malaysia (Selangor, Malaysia). A small part of sample retted above was taken for fiber diameter and surface morphology study. Three replications for each accession were cut into widths and lengths of 2 mm. The bundle of fiber (to increase data taken of the image instead of using single fiber) for each sample were placed into aluminium specimen mounts with slotted head 12.7 mm with tapered end pin 3.1 mm (Electron Microscopy Sciences, Hatfield, United States). The sample was vacuumed and coated with a thin layer of conductive material (gold and platinum) by using SPT-20 Ion Sputter Coater (COXEM, Daejeon, Korea) to prevent electron build up degrading the image quality. The coated sample were then inserted into a motorised chamber of 3-axis XYT sample position stage of scanning electron microscopy (SEM) (EM-30AX Plus; COXEM, Daejeon, Korea). The navigated sample was then extracted by using COXEM Nanostation operating software. The fiber diameter was then calculated as an average of three measurements of the single fiber.

Fiber tensile testing

Five grams of H. cannabinus bast fiber bundle in three replicates for each accession were used for tensile test determination. The test was conducted according to ASTM D885 (1995). The tensile test was done at the Strength Material Laboratory, Faculty of Engineering, Universiti Putra Malaysia (Selangor, Malaysia). A dual column tabletop universal testing machine (INSTRON 3365; Instron, Norwood, MA, USA) was used, with a cell load capacity of 5 kN, at a crosshead speed of 1 mm/min with a gauge length of 60 mm. The standard specifics of sample preparation was followed Amel et al. (2013). 80 gsm A4 paper size (IK Yellow; Goldtech Access Sdn Bhd, Selangor, Malaysia) was cut in similar width (7 cm) of the screw grips and in length 12 cm. A rectangle-shape-hole was made at the center of the paper in width and length of 3 cm and 6 cm (effective gauge length of 6 cm). Both end of the sample was then glued to the paper (3 mm width and 30 mm length at both end of the sample) to avoid the possibility of a sample becoming fractured or slipping in the gripped area.

The lower and upper clamp with smooth face of interchangeable jaws face (Model 2710-004 side-acting screw grips; Instron, Norwood, MA, USA) was adjusted to accommodate the length of the sample. The glued part of the sample was vertically mounted from the lower clamp (the fixed grip) to the upper clamp (the grip in charge of applying tension). The clamp was manually tightened at both knobs at sides of the grips. The tensile strength determination was focused on the gauge length, in which one grip keeps the sample in place, while the other grip pulled at a constant speed until the sample fractured. Once the sample had broken, the tensile testing has officially ended. The tensile properties were recorded as a function of the increase in gauge length (sample elongation during applying tension until fractured). A 5 mm increase in gauge length approximately yields a 20% decrease in fiber strength (Ramesh 2016). Tensile properties of the specimen were then analysed by using Instron Bluehill 3 software (Instron, Norwood, MA, USA).

Statistical analysis

All measurements were analyzed using a factorial analysis of variance (ANOVA) and mean comparison via Duncan’s Multiple Range Test (DMRT) at p ≤ 0.05 (significant difference) and p ≤ 0.01 (highly significant difference). The relationship between the morphophysiological and fiber characteristics were analyzed using bivariate (Pearson) correlation analysis. Interpretation of the correlation coefficient values was based on Ratner (2009). The growth performance of morphological characteristics namely stem height and stem diameter were also evaluated using Simple Scatterplot. The statistical analyses were conducted using IBM SPSS statistics software version 25.0 (IBM Corp., Armonk, NY, USA).

RESULTS

Growth Performance

Stem height and stem diameter are considered as the general guiding criteria for efficient production of fibers in a particular species (Maiti and Chakravarty 1977). Figures 1 and 2 demonstrate growth patterns of the nine H. cannabinus accessions for the four-month cultivation regarding stem height and stem diameter increment, respectively.

Regardless of accession, the stem height increments at the first month after planting (MAP) were in the range from 29.3 to 44.1 cm, and the increment at the fourth MAP were from 43.0 to 55.7 cm. The V36 accession (control), T19 (IBFC China accession), and all four BJRI Bangladesh accessions exhibited strong growth for the first three MAP and slowed down at the fourth MAP, which resulted in higher growth (Table 4) than the other (FH952, T15, and T17) IBFC China accessions, which were slowed down after the second MAP (Fig. 1a). Salih et al. (2014), however, found that plant growth of FH952 (stem height and stem diameter) was greater than the V4383 accession. Meanwhile Sultana et al. (2016) recorded shoot regeneration of HC2 taking minimum days (4.71 days) compared to HC95 accession (7. 41 days).

All nine accessions were found to produce the first bud at 10^th to 15^th node (at stem height 50 to 60 cm) with a minimum of stem height of 70 cm. The first flowering was formed on the 10^th to 15^th node (at stem height 80-90 cm) with minimum stem height was 100 cm. The vegetative growth of all accessions were continued with time.

Fig. 1. Growth performance of nine H. cannabinus accessions; a) stem height increment (cm), b) stem diameter increment (mm) of four month of planting

Stem diameter increment at the first MAP were found in the range from 3.74 to 4.88 mm, while at fourth MAP were found in range from 0.72 mm to 1.60 mm. Stem diameter increment of control accession were observed to decreased considerably only after three MAP compared to other accessions (Fig. 1b). HC95 accession resulted in higher stem diameter increment on the second MAP compared to the first MAP. T15 and V4383 accessions show the same pattern in which stem diameter increment were decreased slightly after second MAP. Meanwhile stem diameter increment of T17, T19, FH952, HC95, HC2, and V4202 accessions were decreased considerably after second MAP.

Most of the control accession plants do not produce buds even after two MAP, compared to other accession in which already produce many buds after two MAP. Ab Shukor et al. (2009) found 50% flowering of V36 accession (control) was 83 to 136 days after planting. Hossain et al. (2012) found kenaf biomass accumulation such as leaf, root, stalk, and wood dry weight was started at 6^th week of growth after planting. Among the nine accessions, the control, V4383, and HC2 accession had the greatest stem diameters, stem dry weights, and total aboveground dry weights, so therefore they portrayed a maximum fiber yield. The results of V36 and HC2 accessions agreed with the findings of Hossain et al. (2014; 2016) and Nasreen et al. (2014) that the accession produced the highest fiber yield.

Morphological and yield characteristics

The results in Table 4 demonstrate all nine accessions allocated more dry matter to shoots than roots. Similar climatic-condition in present study but with different soil properties produced similar results on the control accession plant height (present study (239 cm), Ab Shukor et al. (2009) (240 cm), Omalsaad et al. (2012) (212 cm), and Khalatbari et al. (2015) (231 cm)).

Plant height was found to be significantly different (p ≤ 0.05) among nine accessions. The T17 accession recorded the highest stem heights (245.8 cm) followed by control accession (239 cm), and HC2 accession (236 cm), while HC95 accession had the lowest stem height (216 cm). Hossain et al. (2014) however recorded HC2 as the higher plant height compared to V36 (control) and HC95 accessions. Lower range of stem height in present study (208 to 246 cm) could be due to our planting distance (30 cm) between individual plants.

Results (Table 4) also indicate that there were highly significantly differences (p ≤ 0.01) in stem diameter, root dry weight, leaf dry weight, leaf area, and growth efficiency among nine accessions. The control accession showed the largest stem diameter, stem dry weight, and total aboveground dry weight (15.2 mm, 75.7 g, and 122.3 g, respectively), followed by V4383 (13.8 mm, 63.5 g, and 119.0 g, respectively) and HC2 (13.3 mm, 62.6 g, and 117 g, respectively). Meanwhile the lowest stem diameter and stem dry weight were observed for FH952. The stem diameter of the control accession in the present study (15.2 mm) was much smaller than Omalsaad et al. (2012) (8.00 cm), but almost similar to Ahmad (2011) (21.6 mm), Hossain et al. (2014) (12.0 mm), and Khalatbari et al. (2015) (14.1 mm).

Hossain et al. (2011) found that HC2 produced on average 2 g per plant higher of stem dry weight, root dry weight, and leaf dry weight compared to V36 (control) accession that was grown on 96.4% sand content of soil. HC95 meanwhile produced the lowest biomass (stem, leaf, and root dry weight) in comparison to HC2 and V36 (Hossain et al. 2011; 2016). Stem dry weight FH952 in this finding was in contrast with Qi et al. (2002), who reported that FH952 yield was 15.7% more than the standard cultivar in China. Regardless of accession, fruit dry weight was found to be in the range 15.8 g to 31.9 g. Result (Table 4) indicates that fruit dry weight was not significantly different among the nine accessions.

Table 4. ANOVA and Duncan’s Multiple Range Test of Quantitative Morphological and Yield Characteristics of Nine H. cannabinus Accessions

The highest root dry weight was found from V4383 (32.5 g), followed by HC95 (18.8 g) and HC2 (18.3 g), while the lightest was found from FH952 (13.0 g). Hossain et al. (2011) reported HC2 (11.85 g) had heavier root dry weight compared to V36 (control) (11.5 g) and HC95 (10.8 g) accessions. Ab Shukor et al. (2009) recorded that V36 (control) accession was among the heaviest root dry weight (10.7 g), in which V36 (control) in present study was heavier than reported by Ab Shukor et al. (2009) and Hossain et al. (2011). A highly significant difference (p ≤ 0.01) was found for leaves dry weight among accession. The V4202 produced the heaviest leaves dry weight (29.8 g), followed by V4383 (29.0 g) and HC2 (25.1 g), and the lightest leaves dry weight was the control accession (16.8 g). Hossain et al. (2011, 2016) reported that HC2 had higher leaves dry weight compared to V36 (control) and HC95 accessions.

The results in Table 4 also showed that leaf area and growth efficiency were highly significantly different (p ≤ 0.01) among nine accessions. The biggest average leaf area was found in V4383 (1032 cm²plant^-1), followed by HC2 (796 cm²plant^-1)and T17 (704 cm²plant^-1) accessions, and the lowest leaf areas was T19 accession (155 cm²plant^-1). Hossain et al. (2016) recorded leaf area of HC2 and V36 (control) was 900 cm²plant^-1. However, the highest growth efficiency was found in T19 (0.0187 g cm^-2d^-1) while the lowest was T17 (0.0023 g cm^-2 d^-1).

Physiological characteristics

Photosynthesis is the process in which the energy from light is used to synthesize carbon compounds in foliage leaf (Pallardy 2008; Weraduwage et al. 2015). The physiological characteristics, such as photosynthesis rate (A_net), stomatal conductance (G_s), intercellular concentration of carbon dioxide (Ci), transpiration rate (E_L), instantaneous water use efficiency (WUE_inst), intrinsic water use efficiency (WUE_i), and carboxylation efficiency (A_net/Ci), were measured in this study.

The results (Table 5) indicate that all physiological characteristics were significantly different (p ≤ 0.05) among H. cannabinus accessions, as well as the control accession. The highest A_net was found from HC2 (35.1 mol m^-2 s^-1) followed by T17 (35.0 mol m^-2 s^-1), and control (33.10 mol m^-2 s^-1) accessions, while the lowest rate was found from V4202 accession (27.4 mol m^-2 s^-1). A_net of the control accession in the present study was higher than reported by Khalatbari (2016) at 21.6 mol m^-2 s^-1and Hossain et al. (2016) at 9.9 mol m^-2 s^-1. Hossain et al. (2016) also reported that the A_net of HC2 was 10.11 mol m^-2 s^-1. High A_net has been suggested to contribute to high amount of dry matter production (Table 4) (Salih et al. 2014; Hossain et al. 2016).

The highest G_s was found from HC2 (1.08 mol m^-2 s^-1), followed by control (1.03 mol m^-2 s^-1), HC95 (0.85 mol m^-2 s^-1), and the lowest recorded by T17 accession (0.78 mol m^-2 s^-1). Khalatbari et al. (2016) reported a G_s of V36 (control) of 1.00 mol m^-2 s^-1,which was similar to the present findings. The T17 accession meanwhile might possess better control of stomatal function in water deficit conditions. The highest Ci was found from the FH952 (339.64 mol m^-2 s^-1) followed by V4202 (337.03 mol m^-2 s^-1), V36 (334.77 mol m^-2 s^-1), and the lowest recorded by the V4383 (294.53 mol m^-2 s^-1) accession.

The highest E_L was recorded by HC2 (6.26 mmol m^-2s^-1), followed by V4202 (5.87 mmol m^-2s^-1) and control (5.70 mmol m^-2s^-1), while the lowest was from V4383 (4.54 mmol m^-2s^-1). Khalatbari et al. (2016) recorded that the E_L of V36 (control) was 1.88 mmol m^-2s^-1, and 1.71 mmol m^-2s^-1by Tahery (2011), which was much lower compared to the present study. The highest WUE_inst was found from T17 (7.61 mol mmol^-1), followed by V4383 (7.50 mol mmol^-1), and T15 (6.87 mol mmol^-1), while the lowest was found from V4202 accession (4.88 mol mmol^-1). The V4383 accession had the highest WUE_i (61.9 mol mol^-1), followed by T17 (50.1 mol mol^-1), T15 (43.0 mol mol^-1), and the lowest was HC2 accession (32.8 mol mol^-1).

Table 5. ANOVA and DMRT of Physiological Characteristics of Nine H. cannabinus Accessions

Tensile strength and fiber diameter

Fiber diameter was significantly different among H. cannabinus accessions, including the control (Table 6). The largest fiber diameter (32.6 µm) on average was from the V4202 accession, followed by the T15 (30.75 µm) and T17 (25.05 µm) accessions. Khalatbari et al. (2016) reported fiber diameter of V36 (control) accession was 23.0 µm. Meanwhile H’ng et al. (2009) recorded 24.1 µm, which is similar to this finding. The results also indicated that the fiber tensile modulus of nine H. cannabinus accessions ranged from 10.8 MPa to 77.9 MPa. The three highest tensile modulus values on average were observed from the V4383 (77.9 MPa), FH952 (52.2 MPa), and HC2 (52.0 MPa) accessions, whereas the control accession had an average value of 35.2 MPa.

The three lowest tensile modulus values were observed from the HC95 (16.5 MPa), V4202 (14.9 MPa), and T15 (10.8 MPa) accessions. Both the fiber diameter and tensile modulus were significantly different (p ≤ 0.05) among the accessions. The V4383 accession had a smallest fiber diameter (10.9 µm) with the highest tensile modulus (77.9 MPa). Meanwhile, the V4202 accession had the biggest fiber diameter (32.6 µm) with low tensile modulus (14.9 MPa).

Table 6. Fiber Tensile Strength and Diameter of Nine H. cannabinus Accessions

Correlation Analysis

Morphological characteristics

A highly significant (p ≤ 0.01) strong positive relationship (r = 0.790) was found between stem height and the stem diameter, a moderate positive relationship with stem dry weight (r = 0.556), total aboveground dry weight (r = 0.590), fruit dry weight (r = 0.332), root dry weight (r = 0.362), and a weak relationship with leaf dry weight (r = 0.183) (Table 7). A significant (p ≤ 0.05) but weak relationship (r = 0.152) was observed between plant height and leaf area. This study found a significant relationship between stem diameters and all morphological and yield characteristics except for leaf dry weight and growth efficiency. Meanwhile there was no significant relationship found between stem height and growth efficiency. Among all morphological characteristics, the strongest (p ≤ 0.01; r = 0.848) relationship was found between stem dry weight and total aboveground dry weight.

Stem dry weight was found significantly related with fruit dry weight, root dry weight, total aboveground dry weight, leaf area, but negatively related with growth efficiency. Fruit dry weight meanwhile was significantly associated only with leaf dry weight (p ≤ 0.01; r = 0.217) and total aboveground dry weight (p ≤ 0.01; r = 0.682). Root dry weight and leaf dry weight increases when total aboveground biomass increased (p ≤ 0.01; r = 0.205, 0.373 respectively). Significant positive but weak relationships were found between leaf area with stem height (p ≤ 0.05; r = 0.152), stem diameter (p ≤ 0.01; r = 0.273), stem dry weight (p ≤ 0.01; r = 0.218), and total aboveground biomass (p ≤ 0.01; r = 0.205) depicted increase in leaf area resulted to slightly increases of all above characteristics. Moreover, increasing of leaf area affect to decrease in H. cannabinus growth efficiency (p ≤ 0.01; r= -0.586). The growth efficiency meanwhile decreased (p ≤ 0.05; r = -0.158) with increasing of stem diameter but increased (r = 0.160) with increasing of stem dry weight.

Table 7. Combined Analysis for Correlation Coefficient of Quantitative Morphological Characteristics of Nine H. cannabinus Accessions

Physiological characteristics

Increasing of A_net values resulted from the increase of G_s (p ≤ 0.01; r = 0.619), thus increasing E_L (p ≤ 0.01; r = 0.337), WUE_inst (p ≤ 0.01; r = 0.518), and carboxylation efficiency (p ≤ 0.01; r = 0.937). The Ci (p ≤ 0.05; r = -0.144) and WUE_i (p ≤ 0.01; r = -2.75) however decreased with increasing of A_net. The G_s was found to have a highly significant (p ≤ 0.01) strong positive relationship (r = 0.728) with E_L, and moderate relationship with Ci and carboxylation efficiency.

Table 8. Combined Analysis for Correlation Coefficient of Physiological Characteristics of Nine H. cannabinus Accessions

The increasing of G_s depicted decreases in WUE_inst (p ≤ 0.01; r = -0.193) and WUE_i (p ≤ 0.01; r = -0.683) (Table 8). An increase of Ci meanwhile depicted an increase in E_L of the plant (p ≤ 0.01; r = 0.628) but a decrease in WUE and carboxylation efficiency. The WUE_inst increase with increasing of WUE_i (p ≤ 0.01; r = 0.567) and carboxylation efficiency (p ≤ 0.01; r = 0.739) which demonstrated that the increasing of G_s resulted in increases of E_L and Ci, but a decrease in WUE.

Tensile strength and fiber diameter

Large fiber diameter resulted in a low tensile modulus of fiber (Fig. 2). Inacio et al. (2010) reported that the smaller the diameter, the stronger is the fiber for several natural fibers such as cotton (Gossypium hirsutum), curaua (Ananas erectifolius), jute (Corchorus capsularis), and sisal (Agave sisalana). Weibull analysis of sisal fiber tensile strength conducted by Inacio et al. (2010) also shows an inverse dependence of the tensile strength with the diameter.

In the present study, Fig. 2 showed an inverse correlation between fiber strength and fiber diameter. A fractographic analysis by SEM of the H. cannabinus bast fiber surface in Fig. 3 depicted the thicker fiber with a diameter of d equal to 26.1 µm and above (Table 6). The figure reveals a heterogeneous fracture and covered by a number of impurities (Fig. 3c, 3d, and 3h) suspected to be hemicellulose, lignin, pectin, and waxy substances associated with relatively more fibrils (Tahir et al. 2015). In other words, the fiber tensile modulus less than 20 MPa had voids, impurities, and showed fiber damage on the surface (Fig. 3c, 3d, 3g, and 3h).

Fig. 2. Correlation of fiber diameter and tensile modulus of H. cannabinus accessions

Fig. 3. SEM imagery of nine H. cannabinus accessions; a) V36 (control), b) FH952, c) T15, d) T17, e) T19, f) HC2, g) HC95, h) V4202, and i) V4383

Figure (3g) however demonstrated low tensile modulus with low fiber diameter. This could be due to larger internal area of lumen, thinner cell-wall, and low content of cellulose (Fidelis et al. 2013). Previous studies (Mohamed et al. 2019a,b) showed that fiber lumen diameter and holocellulose of same bamboo species were significantly different (p ≤ 0.01) from the different study location, but not significantly different on fiber cell wall thickness and alpha-cellulose. In the present study, the fractographic analysis indicated that a thicker fiber could break at a stress lower than that required for a thinner fiber. Wirawan et al. (2011) explained that the weak tensile strength could be related to the fiber’s ability to transfer loads to one another, where the effect of crack initiation was dominant with low fiber contents compared to the effect of crack inhibition.

DISCUSSION

Morphophysiological Characteristics and Tensile Strength

Quantitative morphological and yield characteristics are the most important traits to consider for fiber yield in breeding line selection (Li and Huang 2013). Petrini et al. (1994) and Alexopoulou et al. (2000) stated that different cultivars give different responses based on the daylength but stem growth generally declines rapidly following the flower initiation; this likely caused a reduction in vegetative growth of H. cannabinus. In other words, H. cannabinus grew rapidly in the beginning but gradually decreased its rate of growth. Early decreases of stem height increment of China accessions were indicative of an early flowering period. This demonstrated that flowering initiation of China accessions were earlier than control and Bangladesh accessions (Fig. 1a), thus decreased biomass yield of the plant (Table 4). Such postulation agreed with Alexopoulou et al. (2000) that the late-maturing accessions grew taller, exhibited a higher growth rate and developed larger stem diameter as compared to the early maturing ones.

Similar climatic-condition in the present study but with different soil properties, as reported by Ab Shukor et al. (2009), Omalsaad et al. (2012), Khalatbari et al. (2015), produced similar results on the control accession’s plant height. Ahmad (2011) found significantly higher of V36 (control) plant height (310 cm) under similar-climatic condition but different soil properties with 75 cm row spacing. Regardless of accession, lower range of stem height in present study (208 to 246 cm) could be due to our planting distance (30 cm) between individual plants. Higher range of stem height (244 cm to 426 cm) with unbranched habit, however, were found by LeMaheiu et al. (1991) under dense strands condition.

Furthermore, the highest growth efficiency resulted from the accession with the lowest leaf area and low plant growth (T19). As shown in Table 4, it had thicker leaves compared to other accessions. Within leaves, carbon accumulation (C) can be partitioned between leaf area growth and leaf thickening and some were consumed in growth respiration; it was partitioned between expansive growth for water uptake and addition of new mass to the tissue (Weraduwage et al. 2015).

Smaller leaf area with lower production of aboveground dry weight depicted higher growth efficiency, compared to larger leaf area but lower production of aboveground dry weight such as T17, FH95, and HC95. Correlation also depicted a highly significantly negative relationship between leaf area and growth efficiency. A 1% increase in partitioning of leaf thickening with corresponding 1% decrease in partitioning to leaf area growth was found to lead to a 28% decrease in plant mass (Weraduwage et al. 2015). An insignificant different of fruit dry weight among the accessions (Table 4) was attributed to the fact that the axillary buds of the plant that turn into fruit were falling from the plant after ripening, which resulted in a considerable decrease of the fruit dry weight, thus affecting the end result during harvesting stage. This was reported by Scott and Cook (1995) and Rademacher (2015), in cases where the fruit was collected earlier than stem yield for seed production purposes. Meanwhile, the planting date, fertilization, and plant population were altered to maximize seed yields while limiting the vegetative growth plant.

The rate at which transpiration occurs refers to the amount of water lost by plants over a given time period. It is suggested that better intercellular concentration of carbon dioxide resulted in better E_L (Silva et al. 2013). V4383 possess higher WUE_i, which may be due to its higher A_net and lower G_s. In other words, increasing of G_s led to increasing the process of water vapour loss through stomata. V4202 meanwhile possesses the lowest WUE_inst due to its high E_L but low A_net. Water use efficiency (WUE) is an important indicator for leaf carbon and water fluxes at leaf level. It can be determined by WUE_inst and WUE_i that are expressed as the quotients of the diffusive fluxes of CO₂ into the leaf and water vapor out of the leaf during photosynthesis (Farquhar and Richards 1984). This means that V4202 releases a high amount of water during transpiration but low carbon assimilation occurs to produce energy; thus, the water use of the plant was not efficient. This was in agreement with Willis and Balasubramaniam (1968), who reported that E_L is sensitive to plant biomass, but further it is more sensitive to A_net.

The WUE_i of the control accession was much higher than Tahery et al. (2011) (11.3 mol mol^-1). The function of G_s is to absorb CO₂ from the environment to be used for food synthesis, and release oxygen to the environment as the product from the food synthesis (Farquhar and Sharkey 1982). The increase in opening of stomata, however, may release more water from the leaves. This decreases the ratio of carbon assimilation to water loss. Thus plants with high A_net and low G_s provides better WUE_i towards plant growth and possess better control of stomatal function.

Willis and Balasubramaniam (1968) studied that the stomata of leaves may open in response to light, but close again fairly quickly as the stress increases. This condition may increase stress of photosensitive plants (such as H. cannabinus), therefore leading to early flowering and decreased yield. This can be seen in Fig. 1, which indicates that the stem height and stem diameter increment of T17 accession decreased considerably after two MAP. The parameter taken of WUE_inst and WUE_i also depicted that T17, T15, and V4383 accessions were tolerance to water deficit condition and response to light. The lower WUE_i such as the control and HC2 accession meanwhile depicted that the accession need well-irrigation for better yield.

Fiber diameter and tensile modulus were significantly different (p ≤ 0.01) among H. cannabinus accessions. The significance of fiber diameter and tensile strength among accessions agreed with Hossain et al. (2011). The fiber tensile strengths greater than 30 MPa were observed from fibers, which showed rough surfaces and fewer impurities. Meanwhile, the fiber tensile strengths less than 20 MPa had voids, impurities, and showed fiber damage on the surface. The tensile modulus in present study, however, was lower than the previous study by Abdul Khalil and Suraya (2011), as the sample taken at the bottom of the stalk while Rowel and Stout (1998) reported that kenaf fiber length increased from bottom to top.

Correlation

The relationship between stem dry weight and total aboveground dry weight were highest (r = 0.848) compared to the relationships between another morphological and yield characteristics with total aboveground dry weight (Table 8). This indicates that stem dry weight contributed to the greatest proportion of the total aboveground dry weight. This agreed with similar studies by De Andres et al. (2010) and Hossain et al. (2012), where the highest proportion (67.0%) of dry matter was found in the stem of H. cannabinus varieties. Heavier total aboveground dry weight directly produced heavier stem yields, which are crucial for H. cannabinus fiber production.

Fruit dry weight was found significantly associated with all morphological and yield characteristics, except for the root dry weight, leaf area, and growth efficiency. The results (Table 8) also indicate that fruit dry weight contributed to the second largest proportion in total aboveground dry weight, but it cannot be used as a determinant factor as for growth efficiency. Significant positive relationships were found between leaf area with stem height, stem diameter, stem dry weight, and total aboveground dry weight. This indicated that larger leaf area encourages higher photosynthesis rates, which is pertinent for plant growth performance (Clavijo-Herrera et al. 2018). Crowder and Chedda (1982) observed the stem proportion increase as leaf expansion due to an increase in the proportion of lignified structural tissue resulted from photosynthetic process. However, an insignificant relationship was observed between leaf area and leaf dry weight; the leaf area of H. cannabinus accessions from different origins (such as Malaysia, China, and Bangladesh) possess different C partitions in the leaf. This was partitioned between expansive growth for water uptake (such as V4383) and addition of new mass to the tissue (thicker leave such as T19) or both.

Increase in leaf area could explain the decreases in H. cannabinus growth efficiency. Weraduwage et al. (2015) explained that area-based photosynthesis shows a weak correlation with relative growth rate of plant mass. The differences in relative growth rate of plant mass between the accession is very sensitive to variations in parameters related to leaf area including leaf area per unit leaf mass and the proportion of total plant mass invested in leaf, or leaf mass ratio. The results confirmed the finding by Abdul-Hamid et al. (2009) that growth efficiency is low as a consequence of the higher reading in leaf area. The growth efficiency also found significantly (p ≤ 0.05) weak negative relationships with stem diameter (r = -0.158) and stem dry weight (r = -0.160) (Table 6), which indicated that the growth efficiency progressively declined with age of the plant.

Increase in G_s resulted in increased A_net and a further increase in carboxylation efficiency. However, the decrease in G_s was not the only factor that decrease in A_net. The results confirmed the findings in previous studies (Pallas et al. 1966; Radin et al. 1988; Wilkinson and Davies 2002; Sapeta et al. 2013) that in conditions where the G_s is low while the Ci is high (such as in V4202 in present study), there are other factors (such as abscisic acid hormone from the root that minimized water losses due to transpiration) involved in controlling the photosynthesis process. Decreasing of G_s also could be more associated with decreases in E_L (Table 8) that responded to soil moisture content rather than leaf turgor. The finding was similar with Pallas et al. (1966), who found the greatest percentage of open stomata found during water sufficiency.

Increase in A_net indicates increased in G_s, E_L, carboxylation efficiency, and a decrease in Ci; the low Ci triggers the opening of stomata pores (Table 8). Radin et al. (1988) found a significant relationship between A_net and G_s in cotton (Gossypium hirsutum L.) canopy in the field. Even though the closure of stomata is an immediate response to water deficit in order to reduce water loss and increase the resistance to carbon dioxide diffusion, the carboxylation efficiency, however, only was affected after the stomatal closure had already completed. The present study also observed that a condition of high Ci present with low Gs and carboxylation efficiency (Table 5). Tominaga et al. (2018) reported there are uncertainties in calculating Ci when stomata close. The G_s is the determining factor for carbon assimilation, while Ci cannot be used to determine carbon assimilation in water-stress conditions (Da Veiga and Habermann 2013). A biphasic response was reported by Brodribb (1996) that initial stomatal control phase resulted in a substantial reduction in Ci as G_s decreased. As G_s reached a low level, a strong nonstomatal limitation phase was observed, causing Ci to increase as G_s approached a minimum level.

The significance of water to physiological responses of H. cannabinus is important, as the information could be used for genetic improvement regarding intrinsic site conditions. Enhanced A_net and WUE contribute to maintain plant growth for the majority of the accessions. The HC2 accession could be considered for breeding line selection, as it possesses the highest A_net and G_s, which contributed to a high amount of dry matter. Additionally, the V4383 accession could be considered for its high value of WUE_i, which might contribute to good adaptation to low water potential.

The lower tensile modulus of the IBFC, China accessions, except for FH952, might have been due to early growth decreases (third MAP) compared to another accessions where growth decrease at four MAP. Early growth decreases might be related to early maturity cycles, which led to fiber deterioration of IBFC, China accessions (except FH952) during harvest time (fourth month after planting). The fiber tensile strengths greater than 30 MPa were observed from fibers that showed rough surfaces, fewer impurities (cellulosic and non-cellulosic constituents), and no fiber damage. In contrast, the fiber tensile modulus less than 20 MPa had voids, impurities, and showed fiber damage on the surface. The HC95, V4202, and T15 accessions had lower tensile modulus with excessive fiber damages that could affect the fiber mechanical properties. In other words, these fiber accessions were more brittle than other accessions. The control, HC2, FH952, and V4383 accessions could be recommended for breeding line selection as they possessed higher tensile modulus with a rough fiber surface, in which is important for interface bonding of polymer and kenaf fiber (Mardin et al. 2016).

CONCLUSIONS

All measured morphological quantitative and yield characteristics were significantly different among accessions, except for stem dry weight, fruit dry weight, and total aboveground dry weight.
Stem diameter was positively and significantly correlated with all morphological and yield characteristics except for leaf dry weight and growth efficiency. Bigger stem diameter was an indicator of fiber yield in attempts to apply crossing and selection to improve performance
Photosynthesis rate was significantly positively correlated with stomatal conductance, transpiration rate, instantaneous water use efficiency, and carboxylation efficiency. High photosynthesis rate could be an indicator to interpret the pattern of genetic variation of plant assimilation rate and its relation with environmental and agronomic factors.
Fiber tensile modulus was found to be inversely correlated with fiber diameter.
The control, V4383, HC2, and FH952 accessions, can be regarded as a superior H. cannabinus resources possessing high fiber yield, fiber strength, and photosynthetic efficiency for breeding.

ACKNOWLEDGEMENTS

The authors would like to thank the Ministry of Higher Education (MoHE) of Malaysia for funding under a project of the Higher Institution Centres of Excellence (HICoE); Vote No. 6369102. The authors would like to express their special gratitude to Universiti Putra Malaysia for providing laboratory facilities, and also to Mr. Baharom Zainal, Mr. Mohd Kamil Ismail, Mr. Hasnan Mat Isa, and Mr. Hambali Jailani for assistance in field work.

REFERENCES CITED

Ab Shukor, N. A., Hamzah, M. B., Abdul Hamid, H., Salleh, G., and Mohd Nasir, M. F. (2009). “Growth and phenology of kenaf (Hibiscus cannabinus L.) varieties,” Pertanika J. Trop. Agric. Sci. 32(1), 29-33.

Abdul-Hamid, H., Yusoff, M. H., Ab-Shukor, N. A., Zainal, B., and Musa, M. H. (2009). “Effect of different fertilizer application level on growth and physiology of Hibiscus cannabinus L. (Kenaf) planted on BRIS soil,” J. Agr. Sci. (Toronto) 1(1), 121-131. DOI: 10.5539/jas.v1n1p121

Abdul Khalil, H. P. S., and Suraya, N. L. (2011). “Anhydride modification of cultivated kenaf bast fibres: Morphological, spectroscopic and thermal studies,” BioResources 6(2), 1122-1135. DOI: 10.15376/biores.6.2.1121-1135

Ackerson, J. P. (2018). Soil Sampling Guidelines, AY-368-W, Agronomy, The Education Store, Purdue University, Lafayette, USA, 6pp.

Acquaah, G. (2007). Principles of Plant Genetics and Breeding, Blackwell Publishing, Oxford, UK, pp. 246-248.

Ahmad, S., Haque, A., Faruquzzaman, A. K. M., Hussain, M., and Hossain, M. A. (2001). “Field evaluation of kenaf cultivars and their hybrids for their reactions to spiral borer,” J. Biol. Sci. 1(12), 1158-1160. DOI: 10.3923/jbs.2001.1158.1160

Ahmad, D. (2011). “Status of research on kenaf mechanization at Universiti Putra Malaysia,” International Jute Study Group (IJSG), International Seminar on Strengthening of Collaboration for Jute, Kenaf and Allied Fibres Research and Development, International Jute Study Group (IJSG), Dhaka, Bangladesh.

Alexopoulou, E., Cristou, M., Mardikis, M., and Chatziathanassiou, A. (2000). “Growth and yields of kenaf varieties in central Greece,” Ind. Crops and Products 11(2-3), 163-172. DOI: 10.1016/S0926-6690(99)00064-3

Amel, B. A., Paridah, M. T., Sudin, R., Anwar, U. M. K., and Hussein, A. S. (2013). “Effect of fiber extraction methods on some properties of kenaf bast fiber,” Ind. Crop. Prod. 46, 117-123. DOI: 10.1016/j.indcrop.2012.12.015

AOSA (Association of Official Seed Analysts) (2016). AOSA rules for testing seed: Vol. 1, Principles and Procedures. Washington, DC, USA, pp. 225.

ASTM D885. (1995). “Standard test methods for tire cords, tire cord fabrics, and industrial filament yarns made from manufacture organic-base fibers,” ASTM International, West Conshohocken, PA, USA.

Brodribb, T. (1996). “Dynamics of changing intercellular CO₂concentration (ci) during drought and determination of minimum functional ci,” Plant Physiol. 111(1), 179-185. DOI: 10.1104/pp.111.1.179

Chen, B. L., Yang, H. K., Ma, Y. N., Liu, J. R., Lv, F. J., Chen, J., Meng, Y. L., Wang, Y. H., and Zhou, Z. G. (2017). “Effect of shading on yield, fiber quality and physiological characteristics of cotton subtending leaves on different fruiting positions,” Photosynthetica 55(2), 240-250. DOI: 10.1007/s11099-016-0209-7

Clavijo-Herrera, J., Van Santen, E., and Gómez, C. (2018). “Growth, water-use efficiency, stomatal conductance, and nitrogen uptake of two lettuce cultivars grown under different percentage of blue and red light,” Horticulturae 4(3), 1-13. DOI: 10.3390/horticulturae4030016

Crowder, L. V., and Chedda, H. L. (1982). “Herbage quality and nutritive value,” in: Tropical Grassland Husbandry, Longman Inc., New York, NY, pp. 349.

Da Veiga, E. B., and Habermann, G. (2013). “Instantaneously measured traits may detect non-plastic ecophysiological performances in response to drought, explaining distributions of Styrax species in the Cerrado,” Trees 27(6), 1737-1745. DOI: 10.1007/s00468-013-0919-4

De Andres, E. F., Tenorio, J. L., and Walter, I. (2010). “Biomass production and nutrient concentration of kenaf grown on sewage sludge-amended soil,” Span. J. Agric. Res. 8(2), 472-480. DOI: 10.5424/sjar/2010082-1202

Donovan, N. (2001). The Water Relations of Seed Pretreatments and their Effects on the Germination of Radiata Pine Seeds, Ph.D. Dissertation, University of Tasmania, Hobart, Australia.

Evans, J. R. (2013). “Improving photosynthesis,” Plant Physiol. 162(4), 1780-1793. DOI: 10.1104/pp.113.219006

Farquhar, G. D., and Sharkey, T. D. (1982). “Stomatal conductance and photosynthesis,” Annu. Rev. Plant Physiol. 33, 317-345. DOI:10.1146/annurev.pp.33.060182.001533

Farquhar, G. D., and Richards, R. A. (1984). Isotopic composition of plant carbon correlates with water-use efficiency of wheat genotypes. Funct. Plant Biol. 11(6), 539-552. DOI: 10.1071/PP9840539

Faruq, G., Alamgir, M. A., Rahman, M. M., Motior, M. R., Zakaria, H. P., Marchalina, B., and Mohamed, N. A. (2013). “Morphological characterization of kenaf (Hibiscus cannabinus L.) in Malaysian tropical environment using multivariate analysis,” J. Anim. Plant Sci. 23(1), 60-67.

Fidelis, M. E. A., Pereira, T. V. C., Gomes, O. F. M., Silva, F. A., and Filho, R. D. T. (2013). “The effect of fiber morphology on the tensile strength of natural fibers,” J. Mater. Res. Technol. 2(2),149-157. DOI: org/10.1016/j.jmrt.2013.02.003

Fischer, R. A., and Turner, N. C. (1978). “Plant productivity in the arid and semiarid zones,” Ann. Rev. Plant Physiol. 29(1), 277-317. DOI: 10.1146/annurev.pp.29.060178.001425

Gee, G. W., and Bauder, J. W. (1986). “Particle-size analysis,” in: Methods of Soil Analysis. Part 1. Agron. Monogr. 9. A. Klute (ed.), ASA and SSSA, Madison, WI. p. 383–411.

Gomez, K. A., and Gomez, A. A. (1984). Statistical Procedures for Agricultural Research, John Willey & Sons, Inc., Hoboken, NJ, USA.

Hazma, W. N. W., Harah, Z. M., Sidik, B. J., and Natrah, F. M. I. (2015). “Macro and micro nutrients of tropical seagrasses, Halophila ovalis, H. spinulosa and Halodule uninervis in Johore, Malaysia,” Iran. J. Fish. Sci. 14(1), 246-261.

Hossain, M. D., Hanafi, M. M., Jol, H., and Jamal, T. (2011). “Dry matter and nutrient partitioning of kenaf (Hibiscus cannabinus L.) varieties grown on sandy bris soil,” Aust. J. Crop Sci. 5(6), 654-659.

Hossain, M. D., Hanafi, M. M., Saleh, G., Foroughi, M., Behmaram, R., and Noori, Z. (2012). “Growth, photosynthesis and biomass allocation of different kenaf (Hibiscus cannabinus L.) accessions grown on sandy soil,” Aust. J. Crop Sci. 6(3), 480-487.

Hossain, M. D., Hanafi, M. M., Jol, H., and Hazandy, A. H. (2014). “Growth, photosynthesis chlorophyll content and nutrient partitioning of kenaf as influenced by different levels of carbon,” J. Plant Nutr. 37(1), 65-75. DOI: 10.1080/01904167.2013.848888

Hossain, M. D., Musa, H. M., Nuruddin, A. A., Jol, H., and Hamid, H. A. (2016). “Physio-agronomic performance of kenaf as influenced by different carbon levels,” Plant Omics J. 9(1), 61-72.

Hurren, C., Wang, X., Dennis, H. G., and Clarke, A. F. K. (2002). “Evaluation of bast fibre retting systems on hemp,” in: Proceedings of the 82nd Textile Institute World Conference, Cairo, Egypt, pp. 1-9.

H’ng, P. S., Khor, B. N., Tadashi, N., Aini, A. S. N., and Paridah, M. T. (2009). “Anatomical structures and fiber morphology of new kenaf varieties,” Asian J. Sci. Res. 2(3), 161-166. DOI: 10.3923/ajsr.2009.161.166

Inacio, W. P., Lopes, F. P. D., and Monteiro, S. N. (2010). “Diameter dependence of tensile strength by Weibull analysis: Part III sisal fiber,” Materia (Rio de Jenerio) 15(2), 124-130. DOI: 10.1590/S1517-70762010000200006

International Seed Testing Association (ISTA) (2005). Handbook of Method Validation, International Seed Testing Association, Bassersdorf, Switzerland.

Khalatbari, A. M., Jaafar, H. Z. E., Khalatbari, A. A., Abdul-Hamid, H., and Halim, M. R. A. (2015). “The effect of different water regimes on growth, gas exchange rate and water relations of three varieties of kenaf (Hibiscus cannabinus L.) under glasshouse condition,” J. Food. Agric. Environt. 13(1), 103-109.

Khalatbari, A. M., Jaafar, Z. E., Khalatbari, A. A., Hazandy, A. H., and Ridzwan, A. H. (2016). “The physical properties, lignin distribution, chemical composition of fibers and gas exchange rate of kenaf (Hibiscus cannabinus L.) varieties under prolonged water deficiency,” J. Soil Sci. Plant Nutr. 16(3), 716-730. DOI: 10.4067/S0718-95162016005000052

Khan, A., Zheng, J., Tan, D. K. Y., Khan, A., Akhtar, K., Kong, X., Munsif, F., Iqbal, A., Afridi, M. Z., Ullah, A., Fahad, S., and Zhou, R. (2019). “Changes in leaf structural and functional characteristics when changing planting density at different growth stages alters cotton lint yield under a new planting model,” Agronomy 9(12), 859. DOI: 10.3390/agronomy9120859

Kuo, S. (1996) “Phosphorus,” in: Methods of Soil Analysis Part 3: Chemical Methods, SSSA Book Series 5, Sparks, D. L. (ed.), Soil Science Society of America, Madison, Wisconsin, 869-920.

LeMaheiu, P. J., Oplinger, E. S, and Putnam, D. H. (1991). “Kenaf,” in: Alternative: Field Crops Manual, University of Wisconsin, Madison, WI, 5pp.

Li, D., and Huang, S. (2013). “The breeding of kenaf,” in: Kenaf: A Multi-Purpose Crop for Several Industrial Applications, A. Monti, and E. Alexopoulou (eds.), Springer, London, England, pp. 45-58. DOI: 10.1007/978-1-4471-5067-1_3

Li, X., Tabil, L. G., and Panigrahi, S. (2007). “Chemical treatments of natural fiber for use in natural fiber-reinforced composites: A review,” J. Polym. Environ. 15(1), 25-33. DOI: 10.1007/s10924-006-0042-3

Lokhande, S., and Reddy, K. R. (2014). “Quantifying temperature effects on cotton reproductive efficiency and fiber quality,” Agron. J. 106(4), 1275-1282. DOI: org/10.2134/agronj13.0531

Long, S. P., Zhu, X. G., Naidu, S. L., and Ort, D. R. (2006). “Can improvement in photosynthesis increase crop yields?,” Plant Cell Environ. 29(3), 315-330. DOI: 10.1111/j.1365-3040.2005.01493.x

Maiti, R. K., and Chakravarty, K. (1977). “A comparative study of yield component and quality of India bast fibres,” Econ. Bot. 31(1), 55-60. DOI: 10.1007/BF02860653

Mardin, H., Wardana, I. N. G, Pratikto, Suprapto, W., and Kamil, K. (2016). “Effect of sugar palm fiber surface on interfacial bonding with natural sago matrix,” Adv. Mater. Sci. Eng. 2016(7), 1-5. DOI: 10.1155/2016/9240416

Mohamed, J., Hamid, H. A., Nuruddin, A. A., and Majid, N. M. N. A. (2019a). “Anatomical characteristics of Gigantochloa scortechinii bamboo rhizome in relation with hydraulic conductance,” Bioresources 14(4), 9082-9099. DOI: 10.15376/biores.14.4.9082-9099

Mohamed, J., Hamid, H. A., Nuruddin, A. A., and Majid, N. M. N. A. (2019b). “Chemical attributes of Gigantochloa scortechinii bamboo rhizome in relation with hydraulic conductance,” BioResources 14(4), 8155-8173. DOI: 10.15376/biores.14.4.8155-8173

Mohanty, A. K., Misra, M., and Hinrichsen, G. (2000). “Biofibres, biodegradable polymers and biocomposites: An overview,” Macromol. Mater. Eng. 276-277(1), 1-24. DOI: 10.1002/(SICI)1439-2054(20000301)276:1<1::AID-MAME1>3.0.CO;2-W

Nasreen, S. S., Salim, M., and Paul, S. K. (2014). “Effect of variety and seed rate on the yield of kenaf,” Int. J. Sustain. Crop Prod. 9(1), 23-28.

Omalsaad., Osman, M., and Islam, A. K. M. A. (2012). “Characterization of roselle (Hibiscus sabdariffa L.) and kenaf (Hibiscus cannabinus L.) accession from different origin based on morpho-agronomic traits,” Int. J. Plant Breed. 6(1), 1-6.

Pace, S., Piscioneri, I., and Settanni, I. (1998). “Heterosis and combining ability in a half diallel cross of kenaf (Hibiscus cannabinus L.) in south Italy,” Ind. Crop. Prod. 7(2-3), 317-327. DOI: 10.1016/S0926-6690(97)00064-2

Pallardy, S. G. (2008). “Photosynthesis,” in: Physiology of Woody Plants (Third Edition), Academic Press, Cambridge, MA, USA, pp.107-167. DOI: 10.1016/B978-012088765-1.50006-3

Pallas, J. E., Michel, B. E., and Harris, D. G. (19967). “Photosynthesis, transpiration, leaf temperature, and stomatal activity of cotton plants under varying water potentials,” Plant Physiol. 42(1), 76-88. DOI: 10.1104/pp.42.1.76.

Petrini, C., Bazzochi, R., and Montalti, P. (1994). “Yield potential and adaptation of kenaf (Hibiscus cannabinus L.) in north-central Italy,” Ind. Crops Products 3(1-2), 11-15. DOI: 10.1016/0926-6690(94)90073-6

Pettigrew, W. T. (2001). “Environmental effects on cotton fiber carbohydrate concentration and quality,” Crop Science 41(4), 1108-1113. DOI: 10.2135/cropsci2001.4141108x

Qi, J., Lin, L., Lin, P., Li, A., Wu, W., Chen, Q., Zhou, Y., Pan, R., and Cai, J. (2002). “Selection and breeding of Fuhong 952, a new kenaf variety,” Journal of Fujian Agricultural and Forestry University 31(4), 433-436.

Rademacher, W. (2015). “Plant regulators: Background and uses in plant production,” J. Plant Growth Regul. 34, 845-872. DOI: 10.1007/s00344-015-9541-6

Radin, J. W., Hartung, W., Kimball, B. A., and Mauney, J. R. (1988). “Correlation of Stomatal Conductance with photosynthetic capacity of cotton only in a CO₂-enriched atmospheric: mediation by abscisic acid,” Plant Physiol. 88(4), 1058-1063. DOI: 10.1104/pp.88.4.1058

Ramesh, M. (2016). “Kenaf (Hibiscus cannabinus L.) fibre based bio-materials: A review on processing and properties,” Prog. Mater. Sci. 78-79, 1-92. DOI: 10.1016/j.pmatsci.2015.11.001

Rao, N. K., Hanson, J., Dulloo, M. E., Ghosh, K., Nowell, A., and Larinde, M. (2006). Manual of Seed Handling in Genebanks, Bioversity International, Rome, Italy.

Ratner, B. (2009). “The correlation coefficient: Its values range between +1/-1, or do they?,” J. Target. Meas. Anal. Market 17(2009), 139-142. DOI: 10.1057/jt.2009.5

Reddy, A. R., and Das, V. S. R. (1986). “Correlation between biomass production and net photosynthetic rate and kinetic properties of RuBP carboxylase in certain C3 plants,” Biomass 10(2),157-164. DOI: 10.1016/0144-4565(86)90063-6

Rowell, R. M., and Stout, H. P. (1998). “Jute and kenaf,” in: Handbook of Fiber Chemistry, 2^nd Ed., Marcel Dekker, New York, pp. 465-504

Salih, R. F., Abdan, K., and Wayayok, A. (2014). “Growth responses of two kenaf varieties (Hibiscus cannabinus L.) applied by different levels of potassium, boron and zinc,” J. Agr. Sci. 6(9), 37-45. DOI: 10.5539/jas.v6n9p37

Sapeta, H., Costa, J. M., Lourenço, T., Maroco, J., Van der Linde, P., and Oliveira, M. M. (2013). “Drought stress response in Jatropha curcas: Growth and physiology,” Environ. Exp. Bot. 85, 76-84. DOI: 10.1016/j.envexpbot.2012.08.012

Scott, A. W. Jr., and Cook, C. G. (1995). “Growing kenaf for seed in south Texas,” in: Proc. Int. Kenaf Assn. Conf. Irving, TX., 7, pp. 133-135

Senin, A. L. (2016). Growth and Physiological Characteristics of Acacia Species in a Progeny Trial, Master’s Thesis, Universiti Putra Malaysia, Serdang, Malaysia.

Silva, M. D. A., Jifon, J. L., Dos Santos, C. M., Jadoski, C. J., and Da Silva, J. A. G. (2013). “Photosynthetic capacity and water use efficiency in sugarcane genotypes subject to water deficit during early growth phase,” Braz. Arch. Biol. Technol. 56(5), 735-748. DOI: 10.1590/S1516-89132013000500004

Stokes, G. G. (1849). “On the variation of gravity on the surface of the Earth,” Trans. Camb. Phil. Soc. 8, 672-695.

Tahery, Y. (2011). “Comparative photosynthesis and transpiration of three varieties of Hibiscus cannabinus L. (Kenaf),” Afr. J. Agric. Res. 6(8), 2010-2014.

Tahery, Y., Shukor, N. A. A., and Abdul-Hamid, H. (2011). “Comparative water relation of three varieties of Hibiscus cannabinus L. (Kenaf),” Afr. J. Biotechnol. 10(63), 13797-13801. DOI: 10.5897/AJB11.1144

Tahir, P. M., Zaini, L. H., Jonoobi, M., and Khalil, H. P. S. A. (2015). “Preparation of nanocellulose from kenaf (Hibiscus cannabinus L.) via chemical and chemo-chemical processes,” in: Handbook of Polymer Nanocomposites, Processing, Performance and Application, J. K. Pandey et al. (eds.), Springer, Berlin, Heidelberg, pp.119-144.

Teh, C. B. S., and Rashid, M. A. (2003). “Object-oriented code to lookup soil texture classes for any soil classification scheme,” Commun. Soil. Sci. Plant. Anal. 34(1-2), 1-11. DOI: 10.1081/CSS-120017410

Tominaga, J., Shimada, H., and Kawamitsu, Y. (2018). “Direct measurement of intercellular CO₂ concentration in a gas-exchange system resolves overestimation using the standard method,” J. Exp. Bot. 69(8), 1981-1991. DOI: 10.1093/jxb/ery044

Tschieder, E. F., Fernández, M. E., Schlichter, T. M., Pinazo, M. A., and Crechi, E. H. (2012). “Influence of growth dominance and individual tree growth efficiency on Pinus taeda stand growth. A contribution to the debate about why stands productivity declines,” Forest Ecol. Manag. 277, 116-123. DOI: 10.1016/j.foreco.2012.04.025

Wang, Y., Shu, H.-M., Chen, B., McGiffen, M., Zhang, W., Xu, N., and Zhou, Z. (2009). “The rate of cellulose increase is highly related to cotton fibre strength and is significantly determined by its genetic background and boll period temperature,” Plant Growth Regul. 57(3), 203-209. DOI: 10.1007/s10725-008-9337-9

Weraduwage, S. M., Chen, J., Anozie, F. C., Morales, A., Weise, S. E., and Sharkey, T. D. (2015). “The relationship between leaf area growth and biomass accumulation in Arabidopsis thaliana,” Front. Plant Sci. 6, 167. DOI: 10.3389/fpls.2015.00167

Wilkinson, S., and Davies, W. J. (2002). “ABA‐based chemical signalling: The co‐ordination of responses to stress in plants,” Plant Cell Environ. 25(2), 195-210. DOI: 10.1046/j.0016-8025.2001.00824.x

Willis, A. J., and Balasubramaniam, S. (1968). “Stomatal behaviour in relation to rates of photosynthesis and transpiration in Pelargonium,” New Phytol. 67(2), 265-285. DOI: 10.1111/j.1469-8137.1968.tb06383.x

Wirawan, R., Sapuan, S. M., Yunus, R., and Abdan, K. (2011). “Properties of sugarcane bagasse/poly(vinyl chloride) composites after various treatments,” J. Compos. Mater. 45(16), 1667-1674. DOI: 10.1177/0021998310385030

Article submitted: November 20, 2019; Peer review completed: February 29, 2020; Revised version received and accepted: October 5, 2020; Published: October 12, 2020.

DOI: 10.15376/biores.15.4.8883-8908