A study on the histological changes resulting from certain virus infections of the potato

Abstract

A degeneration of the phloem elements of the potato, which occurs in plants suffering from Leaf-roll, was first described by Quanjer (1913). Since them phloem necrosis has been recorded by many workers, some ascribing it to specific pathogenic causes while others state that it occurs in both healthy and diseased plants. Esmarch (1921) states that it is always present in the ripening plant, and v. Brehmer (1923) shows three types of necrosis, viz., Nekrobiose , Obliteration and Necrosis , of which only the last is necessarily due to virus infection. On the other hand, Artschwager (1923) found necrotic changes only in virus infected and injured plants. In this paper an attempt is made to correlate the histopathological changes occuring in virus diseased plants with the external symptoms which they exhibit. A large part of the work is devoted to the morbid anatomy of certain “Streak” diseases, for a detailed account of the external symptons of which see Salaman and Bawden (1932).