Ultrastructural changes to chloroplasts in leaves of eggplant caused by senescence

In order to determine the effect of senescence on the structure and function of chloroplasts in leaf mesophyll cells of eggplant(Solanum melongena Linn.),chloroplasts in immature and senescing leaves were comparatively studied by means of electron microscopy.Chloroplasts in the young leaf mesophyll cells contain cylindrical grana that are connected by stroma thylakoids,rich starch grains,and a few small plastoglobuli that are less than 0.1 μm in diameter.The thylakoids are stained more strongly.However,in the chloroplasts in the old leaves,grana become spherical,thylakoids are stained weakly,stroma thylakoids become less in number,starch grains are reduced or disappeared,plastoglobuli increase in number and size with diameter up to 0.9 μm,and phenolic accumulation appears.It is suggested that leaf senescence of eggplant induces change to thylakoid membrane constituents,inhibits starch accumulation,promotes plastoglobule accumulation,and stimulates phenolic accumulation.