The colloidal stability of enzyme deproteinized natural rubber latex (EDPNRL) was investigated in comparison with the conventional high ammonia (HA) latex. The colloidal stability of EDPNRL was improved by the addition of potassium hydroxide or a combination of potassium hydroxide and amrnonium laurate during compounding. The vulcanization characteristics of EDPNRL were compared with HA latex in a conventional sulphur system using zinc diethyldithiocarbamate (ZDC) as primary accelerator and ZDC in combination with other accelerators namely zinc di-n-butyldithiocarbamate (ZDBC), zinc dibenzyldithiocarbamate(ZDBEDC) and activated dithiocarbamate (Setsit-5). The compounds of EDPNRL with ZDC, ZDBC and their combinations were fast curing. The mechani­cal properties and ageing resistance were within the limits specified for dipped goods. 

In a second phase evaluation of 80 selected wild accessions of Hevea brasiliensis in the 1981 IRRDB Brazilian germplasm collection established at the Rubber Research Institute of India, girth, bark thickness, total number of latex vessel rows, density of laticifers and test tap yield at the age of four years were studied. RRII 105, a popular clone, was used as control. The accessions showed statistically significant differences for all the five traits in the early growth phase. In general, the wild accessions were poor yielders except for one from Mato Grosso, MT/IT/15 – 28/207, with yield (9.72 g/t/t), comparable to RRII 105 (9.40 g/t/t). Certain accessions showed early girthing and longer boles with high but few branches, which are indications of timber production potential. The accessions from Mato Grosso, in general, continued to be superior in the early phase of further evaluation also. Among the top 25 per cent of the wild accessions ranked using rank sum method based on the pooled performance for all the five characters, 20 per cent were from Mato Grosso. Most of the accessions identified earlier as superior for yield and other secondary characters were ranked high. 

The biomass accumulation and total nutrient content in twenty year old rubber (Hevea brasiliensis) trees was quantified by weighing the entire tree by destructive sampling and analysing the nutrient content in different parts of the tree. The balance sheet of nutrients for a planting cycle was worked out, and comparison was drawn between rubber (after three cycles) and forest ecosystems for nutrient reserve and depletion in soils. The branches and trunk accounted for 80 per cent and the roots comprised about 15 per cent of the total dry matter on whole plant basis. The concentration of nitrogen in the leaf and bark exceeded that in the branches and trunk, while calcium concen­tration in the bark was greater than that in the wood / leaf by factors ranging from five to forty times. In general, major portion of nutrients was accumulated in the branches and trunk and was in the order of Ca > N > K > Mg > P. Balance sheet of nutrients indicated that a substantial amount of all the nutrients was removed through biomass and there was a calcium deficit. The depletion of potassium and calcium at 60 cm depth was considerably higher in rubber cultivated soils compared to forest soils. The 'R' factor (per cent of cultivation within the cycle of fallowing and cropping) worked out for rubber plantation in South India was 12.5 per cent, which makes it an agro-forestry ecosystem closely resembling the rain forest. 

Twelve clones of rubber (Hevea brasiliensis) introduced from Malaysia and Thailand were evaluated in a large-scale trial in comparison to the popular clone RRII 105 in India. The performance of these clones with respect  to yield, girth, girth increment, bark anatomical features, incidence of tapping panel dryness, wind damage and pink and powdery mildew diseases are presented. Significant clonal variations existed for all the characters. Clone PB 314 recorded the highest mean yield (79.08 g/t/t) over the first four years followed by PB 255 (76.16 g/t/t). Eight clones yielded significantly higher than RRII 105. The trunk girth in the immature phase was the highest for PB 235 (61.33 cm) followed by PB 280. High girth and uniform growth coupled with high yield of these clones indicate their potential as latex timber clones. 

The efficacy of different weed management methods for immature rubber was evaluated in a field experiment. The treatments included manual (scraping and slashing) and chemical (glyphosate and paraquat + 2, 4-D) methods as well as their combinations to control weeds along the planting strips and plant basins. Application of glyphosate in the entire planting strip was the most cost effective method. The integrated approach of spraying glyphosate in the plant basin and slash weeding the remaining area was also found to be cost effective and eco-friendly.

Light and scanning electron microscopic studies of the leaf surface of Hevea brasiliensis and H. benthamiana revealed that both the surfaces of the leaf lamina are sheathed in thick ornamental cuticle, which is more marked on the abaxial surface. The cuticular ornamentation of both the species appears as a reticulum of buttressed ridges around the stomata on the abaxial surface. The stomatal apparatus appears like a crypt. The buttressed ridges are sculptured with small cuticular continuities that appear as hairy appendages. In H benthamiana the ridges are thick and arranged more or less compactly reducing the width of the stomatal aperture. The cuticle over the laminar nectary is thick and smooth. The curicular pattern on the adaxial lamina is more or less uniform with long parallel striae arranged closely. The thick cuticle is covered with a thin layer of epicuticular wax. Although different interpretations have been given for the surface sculptures of H. brasiliensis, the present study shows that the important component responsible for the leaf features is cuticular in nature. The possible role of cuticle and epicuticular wax in disease resistance and ecological adaptations of Hevea is suggested.