Ultrastructural degeneration of part cells in young leaves of apricot caused by green peach aphids

Abstract：Aphids are plant phloem-feeding insect, sucking the sugary liquids from the host plant＇s vascular system. Green peach aphids （Myzus persicae ） often infest the emerging shoots of apricot （Prunus armeniaca Linn.）. The aphids reproduce rapidly and cause severe distortion of young leaves and inhibit the growth of the new shoots. In order to characterize the ultrastrueture alterations in the infested young leaves, leaf samples were examined by means of transmission electron microscopy. Most cells in the in- fested young leaves were moderately vaeuolated and appeared healthy, but there were a small number of cells that showed excessive vacuolation and cytoplasmic reduction. In the excessively vacuolated cell, a large vacuole occupied almost all the cell＇s total volume, whereas cytoplasm was reduced to very little. The excessive cytoplasmic reduction was concomitant with nucleus deterioration. The nucleus deterioration was symptomized as nucleus shrinkage, extensive accumulation of diffusible osmiophilic compounds, and disappearance of chromatin granules. The excessive cytoplasmic reduction and the concomitant nucleus deterioration led to the subsequent cell distortion. Results suggested that the infestation of green peach aphids caused uhrastructural degeneration to a limited number of cells in the infested young leaves of apri- cot.