Further studies on the ultrastructure of Nicotiana tabacum leaves infected with an Egyptian strain of tobacco mosaic virus

Electron microscopic studies of mesophyll cells of Nicotiana tabacum leaf systemically infected with-an Egyptian strain of tobacco virus revealed several ultrastructural changes. Chloroplasts were spherical in shape; grana, intergrana lamellae [thylakoid] and chloroplast envelope were broken and peripheral reticulum appeared. Virus infection induced an increase in the number of osmiophilic globules, mitochondria and microbodies. Cristae of mitochondria were lost and mitochondrial envelope was disintegrated. There was an increase in crytal-containing microbodies. Virus particles occured in cytoplasm which also showed vacuolation

Histopathology of tomato leaves infected with a heat resistant strain of tobacco mosaic virus

A new heat resistant strain of tobacco mosaic virus isolated from Money maker tomato plantations in Egypt showed severe mosaic mottling and interesting abnormalities on infected leaves. A study of the histopathology of some infected leaves revealed the following: The epidermal cells are pyramid in shape. The upper and lower epidermis are undulated and wrinkled and show several protrusions and multicellular glandular hairs with multi cellular head. Crystals of various sizes and shapes are present in cells of the head. The blade is not constant in thickness. In some leaves there is no differentiation of mesophyll into palisade and spongy. In other leaves the mesophyll is well differentiated. The chloroplasts are large and greater in number. Blisters appear as thick convex, or concave curvatures raised above, or lowered below the surrounding green or light green mesophyll. The mesophyll of the blisters appears hyperplastic. There may he great, moderate, or no bulging of upper side of midrib. Xylem vessels are reduced in number and not arranged in rows. Phloem is riot differentiated and its cells are sometimes big with wavy walls. Xylem and sometimes the surrounding cells degenerate. A complete second leaf may develop on the upper or lower surface of the original leaf