Development of Chloroplast in the Mesophyll Cells of Satsuma Mandarin Foliar Sprayed with Urea

Abstract

The development of chloroplasts in the mesophyll cells of control and urea-applied satsuma mandarin leaves were studied. At 20 days after budding (DAB) active differentiation of chloroplasts in urea-applied trees was evident. However, on a length times width basis, chloroplasts were small in both palisade (1.99 × 0.70 µm ) starch grains. The thylakoid layers per chloroplast were lesser (2.80) in this treatment compared to control (3.72). At 40 DAB, both control and urea-applied trees reached chloroplast maturity, but control trees had bigger chloroplast (4.87 × 2.39 µm 2 ) in the palisade layer cells which contained extremely large and numerous starch grains with few dilated thylakoid layers. Degenerating chloroplasts in the spongy layer cells of control trees were characterized by the disappearance of the outer membrane. While urea-applied trees had smaller chloroplast (4.56 × 2.39 µm 2 ) in the palisade layer. Further, few small starch grains, thylakoid-filled stroma and many lipid droplets were found. Moreover, thylakoid layers were about to dilate but outer membrane of the chloroplasts remained intact in both palisade and spongy layer cells. Compared to the palisade layer cells, chloroplasts in the spongy were bigger (5.32 x 1.95 µm 2 ).