Physiology of virus-infected plants

Abstract

Little information is available on the sequence of physiological changes from virus inoculation to full development of disease symptoms. In this paper, we discuss (1) activity of chlorophyllase, (2) ferrous and ferric iron changes, (3) inorganic and organic phosphorus, and (4) respiration in pigeon pea sterility mosaic infected pigeon pea plants and cassava mosaic infected cassava plants. In both healthy and diseased plants, chlorophylla andb increased with age. However, these were significantly lower in diseased plants than in healthy plants, from early stages. Chlorophyllase activity increased with age, such increase being much steeper in diseased plants. There appeared to be a progressive conversion of ferrous Fe to ferric Fe in diseased leaves. Diseased leaves at all ages had higher levels of total P. There was a greater conversion of inorganic P to the organic form as the disease progressed. Respiration increased with progress of disease up to the production of full symptoms, and dropped thereafter reaching levels lower than those in healthy leaves of corresponding age. In PSMV-affected pigeon pea leaves activity of catalase, peroxidase, ascorbic acid oxidase and cytochrome oxidase increased while polyphenol oxidase activity decreased. Mitochondrial nitrogen was much higher in diseased leaves than in healthy leaves.