The possibility of intercropping cinnamon (Cinnamomum verum) with rubber (Hevea brasiliensis) planted with the standard inter row spacing of 8.1 m was examined. Measurements of light availability and root length density of both the crops in the inter row space and the cinnamon bark yield and its components were recorded for eight years. PAR transmission from the rubber canopy into the middle of the inter row was reduced to 20.6 per cent by eighth year. The length density of fine roots (RLD in cm/ 1000 cm3) of rubber in the inter row increased from 6.4 in the third year to 175.8 in the eighth year in intercropped plots while those of control plots increased from 77.7 to 138.5. RLD of cinnamon in intercropped plots decreased from 51.8 in the third year to 33.5 in the eighth year. Length per stick, weight and bark yield of cinnamon also declined. The reduction in bark yield of cinnamon per bush was 70.5 per cent by the eighth year. The dry matter content of bark was highest (9.36%) when the light level was about 60 per cent. Adverse effects of poor light availability and competition from rubber on cinnamon at this spacing by fifth year were evident. 

Growth and yield of certain Indian and imported clones of Hevea brasiliensis in large scale trials were studies over 15 years of tapping in the traditional rubber growing zone of India. Data on yield and secondary characters like tapping panel dryness and diseases were also collected. In Trial-I, only RRII 105 recorded significantly higher yield (54.5 g/t/t) in BO1 panel while, in panel BO 2, RRII 105, RRII 101, RRII 116 and RRII 103 recorded significantly higher yield than the control clone Tjir 1. In terms of mean yield over 15 years of tapping, clones RRII 105, RRII 101, RRII 116 and RRII 103 were significantly superior to the control. At the age of 23 years girth of clones RRII 114 (112.5 cm) and RRII 116 (107.9 cm) was significantly higher than that of the control Tjir 1 (95.5 cm). In Trial-II, RRIC 100 with the yield of 49.3 g/t/t was significantly superior to the control GT 1 (41.4 g/t/t). At the age of 21 years, clones RRIC 104 (114.0 cm), RRIC 52 (107.8cm) and RRIC 100 (96.5 cm) showed significantly higher girth. In Trial-I clone RRII 105 and in Trial-II RRIC 100 showed overall superiority. 

Dichlorocarbene modification of natural rubber (NR) was carried out by alkaline hydrolysis of chloroform in presence of cetyl trimethyl ammonium bromide as phase transfer catalyst. Modified NR was characterized chemi­cally by chlorine estimation, FTIR, DSC and thermal studies. Extent of modification depended on the time and temperature of reaction. FTIR studies revealed the introduction of chlorine through a cyclopropyl ring to the main chain of NR. Chemical modification considerably increased the Tg of NR as observed from the DSC thermograms. Thermogravimetric analysis showed that the degradation temperature shifted towards the higher side with increased level of chlorination. Modification was accompanied by a change in the physical nature of NR from a soft flexible state to a hard non-tacky form. Peroxide vulcanizates of modified NR showed higher tensile strength than that of pure NR. Solvent swelling studies indicated polar nature of the modified NR and it showed lower swelling in ASTM oils. Oil swelling nature of modified NR containing 15% and more chlorine content was closer to that of hydroge­nated nitrile rubber (HNBR). Due to the polar nature, modified NR mixed well with the polar rubber HNBR and showed improved properties for peroxide vulcanizates.

The response to ethephon stimulation in nine selections of RRII 200 series clones of rubber was studied. Three methods of stimulant application (bark, groove and panel) were imposed. Ethephon at 5% (v/v) concentration was applied on the renewed panel of trees tapped under 1 /2 S d/2 6d/7 system. Monthly yield and dry rubber content (DRC) were recorded for two consecutive years. Results showed considerable clonal variability in yield during the period of study due to stimulation. In general, panel application of the stimulant gave higher yield than the bark and groove methods. DRC was not significantly affected under yield stimulation. Response to stimulation was low in high yielding clones (RRII 208, RRII 203) and high in low yielding clones (RRII 201, RRII 205). 

Oven drying of shelled whole seeds of Hevea brasiliensis at 60 - 180°C over 30 to 180 min resulted in reduction (8.5 to 43.63%) in cyanide content. Drying of chipped seeds was more effective.  Rats fed with feed formulation containing such processed rubber seed kernels did not show any toxicity symptoms although there was increase in cyanide and thiocyanate in the blood serum and urine.

Rubber (Hevea brasiliensis) is clonally propagated through bud grafting. Rough and corky surface of the graft area on the budded stump was observed as a clear symptom of incompatibility of stock and scion. The anatomical conse­quences of this is the development of a deflected type of vascular connection between stock and scion and an impeded type of vasculature. Though the morphological expression could be a consequence of structural incompat­ibility, all structural incompatibilities are not morphologically expressed. An undulating surface topography of the scion bark is another symptom indicating a differential cambial activity at the tangential plane of mutual contact which may lead to a weak connection of vascular tissue leading to reduced strength at the union part. The impeded vascular tissue may lead to a reduced translocation of metabolites from scion to stock and changes in carbohydrate level and starch distribution in scion tissue, as reported in other crops. Dissimilarities of the graft partners for growth potential may be one of the factors influencing incompatibility.