An Ultrastructural Study of Tetranychus mcdanieli feeding injury to the Leaves of ‘Red Delicious’ apple (Acari: Tetranychidae)

Abstract

Cytological changes resulting from foliage feeding by Tetranychus mcdanieli McGregor on ‘Red Delicious’ apple resembled those reported for both natural senescence and induced changes consequent upon fungal and viral infections, cold injury, chemical treatments and mineral deficiencies for the Angiospermae. Injured mesophyll tissues possessed some cells with coagulated protoplasts, some devoid of any visible content, and many with collapsed walls. Mesophyll cells contiguous with or in close proximity to injured ones showed conspicuous fine structural changes occuring within the chloroplasts. These changes were manifested as a marked swelling of the organelle with the granal and stromal thylakoids becoming cup- shaped and the stroma filling the cup; in sectional view these chloro plasts had a characteristic C-shaped silhouette.