Selective Alternations in Photosynthetic Pigment Characteristic and Photoelectron Transport during Senescence of Wheat Leaves

Summary

Aging induced selective changes were monitored both in intact and in detached primary leaves of wheat. We have shown that loss in senescence associated chlorophyll content in the case of wheat leaves, is linked to uniform loss in pigment in chloroplasts and not due to loss in chloroplast number. Analyses of loss of chloroplast absorption spectra both in detached and attached leaves indicate that far red absorbing forms of Chl a (Chl a 692, Chl a 700 and Chl a 708) are extremely sensitive to senescence induced losses. The shift in pH optimum of ferricyanide supported Hill activity of chloroplast during in vivo aging to the pH optimum of phenylenediamine supported Hill activity is indicative of a selective change in electron acceptance site of ferricyanide towards photosystem II. Thus in vivo aging seems to alter the oxidising side of photosystem II.