AbstractsBiology & Animal Science

A knowledge of the processes governing the intake of water and food substances by parasites from the tissues of their hosts is essential for a full understanding of parasitism, but the study of this aspect of the nutrition of phytopathogens is decidedly incomplete. The more destructive parasites which manifest the phenomenon of "action in advance" are considered to be able to satisfy their nutritiona1 requirements from materials liberated from host cells which are killed by some toxin or enzyme secreted by, and diffusing in advance of, the parasitizing mycelium; but the more highly specialized parasites such as the rust fungi employ no such drastic action. The delicate relationship which exists between this latter group of parasites and their hosts has been the subject of voluminous comment, but the physiological mechanism by which these fungi are able to obtain the necessary nutrients from the host cells without causing any marked injury has received little attention or explanation. [...]