The behavior of the fungus Pythium coloratum Vaartaja on onion (Allium cepa L.) roots with a hypodermis of long and short cells was studied. Frequency of encystment adjacent to long versus short cells was compared in live and heat-killed roots. To determine whether the state of suberization of hypodermal cells was correlated with the number of zoospores encysting next to the cell, roots on which zoospores had encysted were stained with toluidine blue to quench most autofluorescence except that caused by lamellar suberin. Penetration of fluorescent long cells, nonfluorescent long cells, and nonfluorescent short cells was compared. Encystment of zoospores on the onion epidermis was more frequent adjacent to short cells of the hypodermis than could be expected for random encystment. More zoospores encysted next to short cells on heat-killed roots than on live roots. Encystment was more frequent over nonfluorescent long cells than over fluorescent long cells. Penetration by the fungus was more frequent into short cells and nonfluorescent long cells than into fluorescent long cells.
Features of the state of the components of the prooxidant andantioxidant system in Allium cepa L. root tissues
