Anatomical and physiological changes of fruit tree leaves during greening and senescence

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The present experiment was designed to determine the effect of fruiting, different nitrogen application, ringing, and water stress on starch accumulation in relation to amylase activity, photosynthetic rate (Pn), and RuBisCo protein in several fruit trees.1. Fruiting effect. The photosynthetic rate was faster in leaves of fruiting limbs during the fruit maturation stage. The chlorophyll was more concentrated in leaves of bearing than in those from non-bearing trees. Non-bearing trees accumulated more starch in th chloroplasts than leaves of bearing trees. The volume of thylakoid decreased with increasing starch size in the chloroplasts.2. Ringing effect. The size of starch grains in the chloroplasts of defruited leaves expanded rapidly in the spongy cell. The chlorophyll content in defruited leaves was lower than in fruiting leaves. In the chloroplasts of defruited leaves, chloroplast-nuclei were localized at the periphery of the plastids. The pn in fruiting leaves was higher than in defruited leaves. Particularly, the Pn of the defruited leaves were under the compensation point.3. Nitrogen effect. The contents of chlorophyll in the leaves declined in parallel with decreasing the nitrogen application in th soil. The starch content in the leaves without or with lower nitrogen application increased more than those in any-nitrogen application plots.The pn increased with nitrogen application.4. Amylase activity decreased with the incease of starch accumulation and with the decrease of chlorophyll content.5. RuBisCo protein was the lowest in the leaves without nitrogen application and accumulation was in inverse proportion to that of starch in the leaves.6. Water stress. The yellowing of the fig leaves by water stress was related to the degradation of the chloroplast and chloroplast-nuclei.7. RuBisCo protein decreased markedly during the natural senescence of theleaves.