Changes in anatomical features, pigment content and photosynthetic activity related to age of 'Irwin' mango leaves.
Karim Ali, Koeda K., Nii N.
Author Affiliation: College of Agriculture, Meijo University, Tempaku, Nagoya 468-8502, Japan.
Journal of the Japanese Society for Horticultural Science 68 : 1090-1098
Abstract : Changes in the anatomical and physiological features of expanding mango leaves were examined to identify the factors that control photosynthetic activity related to leaf age. Studies were conducted using 8-year-old trees grown in 80-litre boxes in a greenhouse. 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 almost reached its maximum area, the chlorophyll content began to increase markedly. With increases in the leaf chlorophyll content, 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 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.