| Abstract: | Following exposure of the youngest mature leaf of uniculm barleyto 14CO2, groups of plants were harvested over a 72 h periodto determine the fate of 14C in the photosynthesizing leaf andin growing leaves and roots. Initially, 14C was mainly presentin sucrose with a little in starch and charged compounds; transportout of the fed leaf was rapid and, by 7 and 24 h, 56 and 93%respectively of the 14C had been translocated about equallyto growing leaves and roots. Sucrose entering meristems wasquickly metabolized to protein and structural carbohydrate (40and 60% of the 14C in these organs at 7 and 24 h respectively),while the remainder was converted to short-term storage productsor intermediary metabolites. By the end of the first day c.35% of the 14C originally assimilated had been lost in respiration. The metabolism of the leaf appeared to be organized on a diurnalbasis, for it exported nearly all its carbon within 24 h ofassimilation. In contrast, some of the assimilate imported intogrowing leaves and, to a lesser extent, roots was not immediatelyused for growth but persisted as temporary metabolites and wassubsequently used for growth in the following days. |
