PHOTOSYNTHETIC ACTIVITIES OF VEGETATIVE AND FRUITING TISSUES OF TOMATO

Photosynthetic activities of different chlorophyll-containing parts of tomato plants (Lycopersicon esculentum Mill. cv, Saporo) were assesse d using chlorophyll fluorescence techniques. Trusses selected for stud y contained near mature, green fruit and measurements were carried out on the truss peduncle, pedicels, calyces, and fruit. Activities of th ese tissues were compared with those of adjacent compound leaves consi dered to be the primary suppliers of photosynthetic assimilates to fru it. All tissues showed high intrinsic efficiencies of photosystem II, measured as F-v/F-m,, in dark-adapted tissue (range 0,77-0,82), Maxima l photosynthetic electron transfer activities varied from 110 to 330 p mol m(-2)s(-1). With increasing photon flux density there was a gradat ion of tissue activity with actual photosynthetic yields, electron tra nsport rates and photochemical quenching coefficients (q(p)) of tissue s decreasing in the order: upper leaf lamina, lower leaf lamina, leaf petiole, truss peduncle, pedicel, calyx, and fruit. The reverse order was found for the rapidity at which absorbed photon energy was diverte d to non-photochemical pathways as photon flux density was increased. The onset of F-o quenching at high photon flux densities suggested tha t all tissues contained a regulated mechanism for dissipating excess e nergy as heat. It was concluded that the non-leaf green tissues of tom ato are quite active photosynthetically and therefore potentially cont ribute significantly to plant growth. At a photon flux density of 185 mu mol m(-2) s(-1), 29% of photosynthetic electron transport activity on a surface area basis was located in tissues other than leaf laminae , with fruit accounting for 15%.