Changes in the physiology of leaves were monitored for their entire life time in tapped and untapped trees of Hevea brasiliensis. At periodic intervals the biochemical components of the leaves, namely, chlorophyll, soluble proteins, free amino acids (FAA), starch, soluble sugars and malondiadehyde (MDA) and the extent of membrane leakage were measured. Total chlorophyll, soluble protein, starch and sugar progressively increased as the leaves matured, but their levels decreased during senescence and wintering. FAA and MDA contents in the leaf increased during the maturation and remained constant before their concentrations increased drastically during wintering. The total chlorophyll/soluble protein ratio decreased sharply and FAA/soluble protein and MDA/total chlorophyll ratios were found to increase abruptly during wintering. Accumulation of MDA indicates severe peroxidative damage of the membrane systems leading to increased membrane leakage during wintering. Results show that tapping led to higher concentrations of starch and soluble sugars in the leaves possibly due to the increased photosynthesis as a result of increased sink activity (exudation of latex). There was more accumulation of MDA and increased membrane damage suggesting increased stress in the leaves of the tapped trees when compared to the untapped trees.
Ageing, Hevea brasiliensis, Malondialdehyde, Membrane damage, Oxidative stress, Senescence, Tapping, Wintering