The occurrence of purple root disease caused by Helicobasidium compactum Boedijn is reported for the first time on rubber in India. The attack is mainly on nursery plants occasionally leading to their mortality.  The presence of distinct fruiting bodies girdling  the collar region, purple coloured fungal growth on root surface and adventitious  root formation are the distinguishing features of the disease.

Some biological parameters of latex, according to the interval between two tappings, were studied in clones PB 235, PB 217 and GT 1 with a view to having a better understanding of metabolic controls and regulation systems involved in latex regeneration.  Three days' interval is needed after tapping to obtain maximal yield indicating complete latex regeneration  in situ for these clones.  Analyses of total solids content in the latex and study  of other  parameters  linked  to energetic  processes of laticiferous cells, such as thiols and inorganic phosphorus content, sugar content and their variations, organic N and total P and ionic (K and Mg) elements were effected. The results obtained lead to link the variations observed in the metabolic activity of laticiferous cells with the tapping intervals and the clones. The results emphasise the importance of metabolic activity in latex regeneration and  thus in production.   Also, they can explain the differences among these clones in their response to stimulation.  They underline the necessity to exploit each Hevea clone according to the metabolic typology of its laticiferous system.

Interrelationships among yield, some physiological factors and soil moisture were studied in Hevea. Data on girth (G), latex yield (LY), rubber yield (RY), latex solute potential (Yp), rubber content (Cr), initial flow rate (F), plugging index (p), latex turgor before and after tapping (pre tap and post-tap Plv), predawn leaf water potential (PD y1), and soil moisture (SM) were collected during   the first  year  of  tapping.  Correlation analysis  was  performed to understand  the relationship existing among the different variables. The contribution of different variables to yield was discerned by subjecting the correlation matrix to path coefficient analysis.  By performing a series of path coefficient analyses, an explanatory model was worked  out for  showing  the dependence  structure and path of action of factors important  for response function. Correlation between LY and RY was close to functional. Correlations of both LY and RY with other variables were similar and the coefficients were higher for LY. The results indicated that among the system variables considered in the study, Yp  and Cr are the primary factors and post-tap Plv, PD Y1 and G are the secondary factors influencing yield, with soil moisture as the driving force. The different variables accounted for 42 per cent of variability in yield.

The diseased laticifers in which latex did not coagulate and the cells nearby in brown bast trees of Hevea brasiliensis  were  observed  using  transmission  electron  microscope. The various organelles in the laticifers showed many abnormal changes.  One of the important changes was membrane turnover disorder.   The membranes, especially the boundary membranes of some lutoids, Frey-Wyssling complexes, nuclei, etc. were disorganised.   The membrane materials appearing as myelin-like structures abnormally accumulated in diseased laticifers.  One of the significant characteristics of the nucleus in diseased laticifer was the frequent presence of bundles of straight microfibrils, which might be microfilaments, about 5 nm in diameter.  The nuclei were often found with decreased contents and partly disorganised nuclear membrane.

Two extractants were compared for the estimation of available K, Ca and Mg in acid soils under rubber. Wide variation in soil K, Ca and Mg was recorded between the samples. Numerically higher values were obtained for available K with ammonium acetate extraction. For Ca and Mg more quantity was extracted with Morgan's extractant. Correlations between soil test values and corresponding leaf nutrient concentrations indicated that both extractants are equally good for evaluating the availability of K and Ca. Considering the non-corrodable nature and being the universal extractant, ammonium acetate was found to be the better choice. A better extractant has to be identified for available Mg.

Oxygen-induced  polymerisation  of blends of fatty acids from rubber seed (RSA), watermelon seed (MSA) soyabean (SBA) and linseed (LSA) was done with a view to optimising the drying performance of the semidrying  ones for development  of alkyd resin paint binders.   The results obtained showed  two types of behaviour  in oxygen absorption: a linear response by LSA/RSA and SBA/RSA blends in which oxygen absorbed increased directly with the amount of the more drying fatty acid; and a synergistic response by MSA/RSA, MSA/LSA blends in which oxygen absorption showed optimum values between 40-50 wt per cent of MSA. This behaviour by MSA holds good promise for development of alkyd resins.