Journal of the Rubber Research Institute of Sri Lanka
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Item Use of blends of glove waste and natural rubber in rubber products manufacture(Rubber Research Institute. Agalawatte, 1996) Seneviratne, W.M.G.; Kumara, P.H.S.; Abeykoon, A.M.C.Substantial amount of defective examination gloves are rejected in glove manufacturing factories in Sri Lanka. These glove rejects cause severe environmental hazards. A series of experiments were therfore carried out to investigate the possibility of recycling these glove rejects and using them as a blend or a filler in the manufactures of rubber products. The results of the experiments indicate that appraciable quantity of recycled glove waste can be blended with NR to give properties comparable to that obtained from NR alone.Item The effect of tapping on the assimilation rates of Hevea brasiliensis Muell. Arg. leaves(Rubber Research Institute. Agalawatta, 1990) Nugawela, A.; Aluthhewage, R.K.The CO2 assimilation rates at leaf level were compared in tapped and untaped trees of two Hevea brasiliensis genotypes. In both genotypes, the CO2 assimilation rates of the leaves in the upper stratum were lower in tapped trees. Simmilary, in young microtapped plants the CO2 assimilation rates were lower than in the untapped plants. The decrease in CO2 assimilation rates due to tapping cannot be attributed to an increase in either stomatal or mesophyll limitations. Tapping increases the sink demand for photo assimilates, but it also results in the loss of water, inorganic nutrients and proteins from the plant. Loss of water, inorganic nutrients may results in lower CO2 assimilation rates of the tapped trees. In the long-term this could result in lower sucrose content in the latex. This may be a probable cause for the physiological disorder, tapping panel dryness in rubber.Item Seasonal variations in nodule activity of Pueraria phaseoloides (Roxb) Benth(Rubber Research Institute. Agalawatta, 1990) Jayasinghe, C.K.; Parker, C.A.; Kulasooriya, S.A.The age of Pueraria phaseoloides plants had a marked effect upon the rate of acetylene reduction in their nodules. Acetylene reduction activity increased with the age of the plant and maximum efficiency of nodule activity was detected 60 days after sowing, followed by a marked decline on the 120th day and continued at a low rate. Dry matter yield and total nitrogen in plants was more or less constant thrugh out the assay period.Item An investigation on oil of rubber seed (Hevea brasiliensis)(Rubber Research Institute. Agalawatte, 1996) Njoku, O.U.; Ononogbu, I.C.; Owusu, A.J.Y.Oil from seeds of hevea brasiliensis traditionally used as thickening agent for saurce preparation was isolated, and its physical and chemical characteristics determined. Saponification yielded saturated and unsaturated fatty acids which were seperated by preferential crystallization using organic solvents. Methanol, Ethnol, Hexane and Acetone were found effective solvents inthis regard. Gas liquid chromatography (GLC) revealed large amounts of C18 fatty acids as well as traces of other fatty acids. The iodine values show that the solvents used in this study gave excellent yields of fatty acids with acetone being the most effective as a crystallization solvent to oil ratio 3:1 at 5 oC.Item Towards shorter immaturity and improved yields by mulching with rice straw(Rubber Research Institute. Agalawatta, 1992) Samarappuli, L.; Yogaratnam, N.; Samarappuli, P.; Mitrasena, U.In this study with immature Hevea brasiliensis, multing with paady straw around the base of the tree was found to be a better agronomic practice than growing leguminous cover crops such as Pueraria phaseoloides and Desmodium ovalifolium or allowing natural vegetation to grow in the inter-row area. Girthing had been much higher with mulching which resulted into reduction of the immature, unproductive period by approximately 18 and 12 month in comparison with naturals and creeping legumes respectively. In addition to early tapping, yield of latex was also higher during the early stages, increases in the region of 33perc. and 40perc. in comparison with creeping legumes and naturals respectively. The present value of the benefit achieved from mulching amount to Rs. 31,088/= per hectare of which Rs. 19,740/= is due to extra yield and the balance of Rs. 11,348/= is saving on inputs as a result of early maturity. Consequently, a net present value (NPV) of Rs. 7.8 million at national level can be achieved with the above practice at 50perc. level of adoptionItem Evaluation of performance of flat bark crepe, scrap crepe and RSS in tyre retread compounds(Rubber Research Institute. Agalawatta, 1993) Kalyani, N.M.V.; Gunewardena, A.Item Hand pollination of Hevea brasiliensis in Nigeria (1984-1990). comparison with open pollinated field data(Rubber Research Institute. Agalawatta, 1990) Olapade, E.O.; Omkhafe, K.O.Artificial hand polinations of Hevea brasiliensis were done at the Rubber Research Institute of Nigeria (RRIN) from 1984-1990: these involved 28,887 female flowers from which only 7.60perc. mean fruit set was obtained while only 5.13perc. of the flowers formed fruits that reached maturity. A correlation value of 0.65 was obtained between number of female flowers pollinated and fruits set. Clonal variations were observed for flowers production in the open pollinated field with very high correlation of +0.9 between male and female flowers. Clones PB 5/51 and RRIM 707 produced the highest number of both male and female flowers. The mean male to female flower ratio was 14.1. Male flowers had a higher correlation coeffieciency of r=0.32 with fruit set than emale flowers with r=0.05. An estimate of 15perc. fruit set was obtained under natural open field pollinations in 1989 while only 8.8perc. of the flowers formed fruits that reached maturity. Only about 64perc. of the 64 perc. of the fruits set under both artificial and natural open pollinations reached maturity. While about 36perc. abortions of fruits took place. The implications of these results are discussed.Item Acclimatization of micropropagated plants of Hevea(Rubber Research Institute. Agalawatta, 1993) Seneviratne, P.; Wijesekera, G.A.S.; De Soysa, G.M.In vitro produced Hevea shoots were successfully acclimatized to outdoor conditions by controlling the ambient conditions, mainly the humidity. Shooots, longer than 5 cm and with some leaves attached performed better. Shoots without roots produced shoots soon after their transfer to soil and the root development and the acclimation succes was better than in the rooted shoots. Use of a concentrated auxin solution, to soak the bases of the shoots or to incoroperate into soil improved root induction. The growth of the aerial part and the root system of the micropropagated plants were comparable to those of embryo cultured plants, up to one year of growth, but the field performance is yet to be monitored.Item Performance of some RRIC 100 series clones under different soil moisture regimes(Rubber Research Institute. Agalawatta, 1992) Samarappuli, L.; Yogaratnam, N.; Hettiarachchi, R.Results obtained on the performance of recently developed RRIC 100 series clones when sujected to water deficit situations are presented in this paper. The plant diameter of RRIC 121 and RRIC 102 was found to be superior to other clones tested such as RRIC 100, RRIC 110 and PB 86 even at the very low soil moisture level of 10% available water. Similar results were recorded in relation to plan height, number of whorls and relative growth rates of clones RRIC 121 and 102 even under low soil moisture conditions. Data obtained also showed that clones RRIC 102 and 121 had the highest plant nitrogen and potassium contents. Moreover, even under very low soil moisture levels plant P content was greater in clones RRIC 121 and 102. Most of the data on growth are also consistat with the physiological parameters such as leaf water protential (LWP) relative water content (RWC), transpiration rate (TR) and leaf diffusive resistance (LDR). It was further noted that the LWP and RWC were highest while TR was lowest in clone RRIC 102. Moreover, the clone RRIC 102 had the highest LDR compared to other clones, confirming the ability of this clone in maintaining a higher water holding capacity under low soil moisture conditions.Item Control of variability in experiments with rubber using covariance technique. a review(Rubber Research Institute. Agalawatta, 1997) Wijesuriya, B.W.; Thattil, R.O.Comparatively little has been published on experimental techniques and statistical methods in rubber.This paper is a review of available literature on the use of covariates in experiments falling into immature and mature stages of rubber.The main objective is to encourage researchers to collect appropriate pre-treatment records to adjust the post.treatment variables so as to obtain high precision of results.In this connection,the effectiveness of rubber yield,girth and panel variables as pre-treatment records during the mature stages;seed and budded stump weights as covariates during the immature stages are discussed.The use of double covariance and other possible approaches to minimize initial variability in fertilizer,pest and disease,weed and green house experiments are also discussed.