1999 Volume 68 Issue 6 Pages 1090-1098
Changes in the anatomical and physiological features of expanding leaves of mango (Mangifera indica L., cv. Irwin) were examined to identify the factors that control photosynthetic activity related to leaf age. Anthocyanin content increased before leaf enlargement but decreased rapidly as the lamina expanded. Immature leaves soon after budbreak were yellowish green with a small amount of chlorophyll. When they were stained with 4', 6-diamidino-2-phenylindole (DAPI), some chloroplasts fluoresced red, whereas others were yellowish in the same mesophyll tissues. When the leaf reached almost its maximum area, the chlorophyll content began to increase greatly. With increases in the chlorophyll content of the leaves, the intensity of staining with DAPI increased. Stomata did not differentiate in the leaves soon after budbreak. When leaves reached 28.6 cm2, guard cells of stomata appeared. Green and mature leaves contained higher concentrations of ribulose bisphosphate carboxylase-oxygenase, as detected by immunoblotting after SDS-polyacrylamide gel electrophoresis than did young, immature leaves. The photosynthetic rate and the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm) were consistently lower in young, immature leaves than in mature leaves. Oxygen evolution and Fv/Fm ratio increased with an increase of chlorophyll content but Fv/Fm increased much faster during rapid chlorophyll synthesis at the beginning of leaf enlargement than later when the increase in chlorophyll decelerated.
