Journal of the Rubber Research Institute of Sri Lanka
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Item Accumulation of free proline in bark and latex of Hevea brasiliensis affected by brown bast(Rubber Research Institute. Agalawatta, 1986) Wickramasinghe, S.I.; Yapa, P.A.J.; De Soysa, T.V.W.Free proline accumulation in clone RRIC 101 of Hevea brasiliensis was investigated. The bark and the latex samples collected from both healthy and brown bast effected trees were analysed for free prline content. The average bark proline concentration/unit present in the brown bast trees was found to be considerable higher (P = 0.10) than that of healthy trees. The accumulation of free proline in latex was found to be significant in brown bast trees.Item Gas exchange parameters for early selection of Hevea brasiliensis Muell. Arg(Rubber Research Institute. Agalawatte, 1985) Nugawela, A.; Aluthhewage, R.K.Selecting high yielding progeny from Hevea breeding programmes is a money and time consuming approach and limits the progress of breeding, Girth, bark thickness, numberof lates vessel rings, latex vessel density and first few years yield of 7-8 year old Hevea budding are reported to be correlated to the yield potential. These parameters are used by some breeeders for a primary selection using smalle scale clone trials. Latex is biosythesised from sucrose in latex vessels and the potential of sucrose supply to latex vessels depends on CO2 assimilatory capacity of the canopy and the partitioning of assimilates. Attempts were made to estimate the mean CO2 assimilatory capacity of a healthy and a matur eleaf whole in year old Hevea clonal buddings. Preliminary studies show the mean CO2 assimilatory capacity of a whole and its ratio with water use efficiency value to be correlated qith yield potential. These observation suggest that effective selection of clones for further testing in large scale clone trials could be done on this basis, when buddings are around a year old.Item Variations involved in field measurements of transpiration rates and stomatal diffusive resistance of Hevea brasiliensis Muell. Arg. clones and the relationship of the latter with net photosynthetic rates(Rubber research Institute. Agalawatte, 1984) Nugawela, A.; Wickremasinghe, W.N.; Aluthhewage, R.K.Variance components and their percentage contribution to total variation during field measurements of stomatal diffusive resistance (DR) and transpiration rates (TR) were studied for Hevea clones. Variance from the plant component was much higher than other components viz., leaves of the same plant and determinations of the same leaf. DR, TRand coefficient of varian for DR and TR varied significantly with leaf age and time of the day. The three leaflets in a leaf were similar in respects to DR and TR. Within a whorl, the comparatively smalle leaves at the top of differed significantly withrespect to DR and TR from the rest. DR and Tr of clones RRIC 100, RRIC 103, RRIC 45, PB 86 and IAN 710 were significantly different at 0.1perc. level. Initial studies show stomatal diffusive resistance to have a tendancy to be correlated with net photosynthetic rates (NPR). Other possible factors that might bring about clonal differences in NPR are discussed.Item Effect of soil moisture on establishment success of different planting techniques in rubber(Rubber Research Institute. Agalawatta, 1993) Samarappuli, L.; Yogaratnam, N.; Hettiarachchi, R.Item Role of potassium on growth and water relations of rubber plants(Rubber Research Institute. Agalawatta, 1993) Samarappuli, L.; Yogaratnam, N.; Karunadasa, P.; Mitrasena, U.; Hettiarachchi, R.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 The positional effect of the explant on In vitro growth of axillary buds of Hevea brasiliensis(Rubber Research Institute. Agalawatte, 1996) Senaviratne, P.; Flegmann, A.W.; Wijesekera, G.A.S.Apart from the high apical dominance showed in shoot explants of hevea, the location of the node in the shoot, seems to play a vital role in in vitro axillary bud proliferation. Better performance was observed when the axillary buds harvested as nodes, were not too close and also not too far from the apex as measured by the primary axillary shoot growth. This was true for both juvenile and mature arigin materials. Furthermore, "active" nodes were superior to "dormant" nodes.Item Can tapping panel dryness of rubber (Hevea brasiliensis) be minimised at field level with better management?(Rubber Research Institute . Agalawatta, 2007) Senevirathna, A.M.W.K.; Wilbert, S.; Perera, S.A.P.S.; Wijesinghe, A.K.H.S.Item Physiological yield determinants of sun and shade leaves of Hevea brasiliensis Muell. Arg(Rubber Research Institute of Sri Lanka. Agalawatte, 1995) Nugawela, A.; Ariyawansa, P.; Samarasekera, R.K.Item Root development in Hevea brasiliensis in relation to management practices(Rubber Research Institute of Sri Lanka. Agalawatte, 1996) Samarappuli, L. and othersFeeder root density was shown to be significantly different between distances from the base of the rubber plant and in their vertical distribution with the highest percentage of roots being in the surface soil layers, 0-10 cm and 10-20 cm in the region of 120 cm circle. The amount of feeder roots in the surface soil was more than 75 per cent of the total feeder roots and only 17.2 per cent and 1.9 per cent of the total root weights were found in the lower soil layers, 20-50 cm and 50-90 cm, respectively. Statistical calculations (coefficient of variation) of volumetric moisture content data indicated that the distance 60 cm from the tree at surface soil layers would appear to give the highest variation. Significant positive correlations were found between fine sand content (<200µ diameter) and root density, while clay content was negatively correlated to root density. Root density had the tendency to decrease with increasing soil bulk density, but to increase with increasing soil organic carbon content. There was a significant difference in root density between clones. Vigorous clones like RRIC 102, RRIC 121, RRIC 100 and RRIC 110 had more feeder roots than a less vigorous clone like PB 86. Feeder root development also significantly differed between different establishment practices. Differences in the development of feeder roots were also shown to be significant with different soil moisture levels and potassium levels. Moreover, data obtained show that there was more vigorous feeder root development under mulching than under legume cover or natural cover.