RESEARCH ARTICLE J.Natn.Sci.Foundation Sri Lanka 2018 46 (2): 179 - 185 DOI: http://dx.doi.org/10.4038/jnsfsr.v46i2.8418 Effect of ethephon stimulation on natural rubber latex properties; new insight into ethephon stimulation 1* 1 1 Rubber Research Institute of Sri Lanka, Ratmalana. 2 Department of Chemistry, Faculty of Applied Sciences, University of Sri Jayewardenepura, Gangodawila, Nugegoda. Revised: 14 November 2017; Accepted: 21 December 2017 * ; https://orcid.org/ ) Abstract: tool to overcome issues such as high cost of production, plantation industries. When developing a protocol for ethephon effect on associated latex quality parameters. Therefore, this study elucidated the effect of ethephon on dry rubber yield rheological behaviour and physiological parameters. Five stimulated latex as the control. The results revealed that all the S/2 d3 harvesting system. Keywords: Ethephon concentration, Hevea brasiliensis, latex quality, stimulation. INTRODUCTION Stimulation to overcome issues such as high cost of production, in rubber plantations (Vijayakumar et al., 2001; Rodrigo et al., 2012). the intensity of harvesting, ethephon stimulation is used as an excellent strategy to obtain desirable yield Stimulation is not to obtain high yields but to attain a yield more or less equal to any baneful secondary effects of recommended dosages of stimulant is of utmost importance and great care should be taken to avoid any and application frequency. Ethephon directly affects the and may also affect latex physico-chemical parameters 2+ effect of ethephon on latex yield, quality and associated concentrations have not been studied previously. This effect of different concentrations of ethephon on latex physiological and rheological behaviour, and quality of METHODOLOGY Rubber Research Institute of Sri Lanka. Each treatment 180 A.P. Attanayake et al. June 2018 Journal of the National Science Foundation of Sri Lanka 46(2) same tapper in order to avoid tapper variability. Samples means and standard deviation of pooled samples for each for the analysis of sucrose and thiol content. Rest of the laboratory for the analysis of latex quality parameters. The data represent the means and standard deviation of samples collected up to 10 tapping days after ethephon for mean values of each ethephon concentrations and using reduced glutathione. average daily yield and number of trees tapped. Analysis of dry rubber content and total solids content 124:2014 standards, respectively. Volatile fatty acid o standard RRISL method. One gram of the latex sample 4 4 2 O) and 4 mL of the colour changed from purple to blue. The determination m = molarity of EDTA solution (moldm-3), V = volume of EDTA (dm3 24.312 x m x v x1000Mg Content (ppm) = w RESULTS AND DISCUSSION Figure 1: Variation of (a) serum thiol content and (b) latex volume in latex of RRIC 121 genotype T h io l co n ce n tr at io n (m M ) Ethephon concentration (%) L at ex v o lu m e (m l/ tr ee /t ap ) Ethephon concentration (%) L at ex v o lu m e (m L /t re e/ ta p ) (b) Ethephon stimulation on natural rubber latex properties 181 Journal of the National Science Foundation of Sri Lanka 46(2) June 2018 further increase (Figure 1a). might have a dual role in latex metabolism and latex et al., 1986). Thiols are the 3 % may be due to enhanced in vitro synthesis of reactive oxygen species (ROS). The free toxic oxygen radicals et al., 1996). Thiols act as a potential activator for key enzymes such as invertase and pyruvate kinase (Jacob et al., 1981). In unstimulated trees, average latex sucrose content sucrose content tended to decrease gradually reaching sucrose consumption is compensated by increased migration of sugar to the treated bark zone by the sink effect of stimulating substances, and higher doses did not improve the production but resulted in a greater sucrose expected due to exhaustion of the carbohydrate reserves further increase of ethephon dosage beyond 3 % caused simultaneous reduction in rubber yield. Therefore, high ethephon doses. an average dry rubber content of 43 % resulting in 84 g of daily dry rubber yield per tree. The volume of latex ethephon concentration (Figure 1b). Dry rubber content concentration. At 3 % ethephon concentration latex latex reduced to 37 %. When increasing the strength of stimulant further, the volume of latex reduced to 210 mL latex volume resulted at 3 % ethephon concentration and S u cr o se c o n ce n tr at io n ( m M ) V o la ti le f at ty a ci d n u m b er Ethephon concentration (%) VFA SUCROSE Variation of serum sucrose content and volatile fatty acid on many factors such as clone, season and system of tapping. Sucrose provides metabolic energy for rubber on sucrose availability in latex vessels determining the possibilities for an enhancement of invertase activity after treatment (Tupy, 1973). The reduction of sucrose content up to 3 % might be due to the higher metabolic utilisation of sucrose for rubber production and diminished entry of sucrose from the surrounding cells into latex vessels Y ie ld ( g ra m s/ tr ee /t ap ) M ag n es iu m c o n ce n tr at io n (p p m ) Ethephon concentration (%) MAGNESIUM YIELD Variation of serum magnesium concentration and dry under S/2 d3 system 182 A.P. Attanayake et al. June 2018 Journal of the National Science Foundation of Sri Lanka 46(2) Rubber yield of a particular clone in commercial latex production is probably determined not only by the ethephon dosage controlling the biosynthesis of rubber, but also by physiological and biochemical processes the application of 3 % ethephon (100.73 gt -1t -1). Further increase of strength of ethephon negatively affected the dry rubber yield, resulting in 4 % decrease over the yield the above observations that application of higher doses frequency is reduced beyond once in three days. There materials lost during tapping. Total solid content, dry rubber content and non-rubber content respectively. With the application of 1 % ethephon, both reduced to 34.6 and 31 %, respectively (Figure 4). With the gradual increase of ethephon concentration, indirectly indicates the non-rubber content in latex (Figure 4). In unstimulated latex, the average total non- non-rubber content by 26 %. (Do Kim et al., 1996) and those parameters have an accentuated during the 2nd or 3rd subsequent tapping and accounts for the process of increased production (Jacob et al proteins, carbohydrates, lipids, phospholipids and nucleic acids can be attributed to the enhanced re-synthesis of higher dosage of ethephon the biosynthesis process up- regulated via enhancement of invertase activity, and up - regulated the physiological processes to regenerate cell inspite of the nutritional level of the tree. N o n - ru b b er c o n te n t (% ) T o ta l so li d c o n te n t, d ry r u b b er co n te n t (% ) Ethephon concentration (%) ethephon concentrations Volatile fatty acid number The volatile fatty acid content in latex increased Average volatile fatty acid (VFA) number in unstimulated ethephon, VFA number has increased to an average value Increase of the VFA value can be attributed to achieving optimum condition in latex for bacterial that VFA originate from sugar degradation and their quantity is indeed one of the most important parameters et al., 2014). Although serum sucrose concentration reduced Ethephon stimulation on natural rubber latex properties 183 Journal of the National Science Foundation of Sri Lanka 46(2) June 2018 in VFA value could be observed. Therefore, this can be VFA value may contribute to the colloidal de-stability. Therefore, special precautions should be taken for the Magnesium content from 183.11 ppm in unstimulated latex to 139.30 ppm. further reduction in magnesium content reaching up to (Figure 3). The reduction of serum magnesium content ' et al reduction in serum magnesium content can be attributed to the enhancement of biosynthesis process as this cation higher concentration of this cation deactivates the rubber et al hand, translocation of this cation to the lutoids provides 2+ concentration rubber formed (Fujii et al., 1980). distribution, branching and chain entanglements. These particles is extremely high. As the shear rate increases, V is co si ty ( ce n ti p o is e) Ethephon concentration (%) CONCLUSION With the increase of ethephon concentration from total solid content (Figure 6). This erratic variation in behaviour of natural rubber latex. With increasing ethephon concentration above 3 %, most of the non- lutoid particles. During shearing, lutoid particle breaks similar to the fractionation process and contents come o (spindle no. 2) V is co si ty ( ce n ti p o is e) Shear rate (rpm) 184 A.P. Attanayake et al. June 2018 Journal of the National Science Foundation of Sri Lanka 46(2) in non-rubber content and volatile fatty acid content as a result of increased level of ethephon. Enhanced ethephon concentration facilitated the reduction in latex viscosity and the reduction of serum magnesium recommended dosage may only provide the optimum results and excessive use of ethephon may deteriorate the expected results. REFERENCES 1. of natural rubber latex on physio-chemical properties of rubber. PhD thesis Sri Lanka. 2. diffusion of concentrated monodisperse and bidisperse polymer lattices. 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