EXPRESSION OF CHLOROPLASTIC GENES DURING AUTUMNAL SENESCENCE IN A DECIDUOUS TREE POPULUS DELTIODES

In Populus deltoides, a deciduous tree, the development on new leaves starts in the month of March, the leaves reach maturity by October and fall by December. Changes in the composition and function of the phot osynthetic apparatus were analysed during autumnal senescence. With th e progress of senescence, there was an initial increase followed by a decrease in the steady state levels of psbA, psbD/C and psaA/B gene tr anscripts. Decrease in the steady state level of D1 protein was faster than that of Cytochrome f. The decline in LHCP level was seen only du ring late senescence. Although the leaves continue to look green and h ealthy till late November, the electron transport driven by individual photosystems started declining by October end suggesting the onset of senescence.