Resistance of Cucumber Seedlings to Damping-Off as Related to Age, Season of Year, and Level of Nitrogen Nutrition

Abstract

Cucumber seedlings were grown in sand culture at high and low levels of nitrogen nutrition during several different seasons of the year. The seedlings were artificially inoculated at different ages with a fungus of the Pythium type, causing the damping-off disease, and the relative resistance or susceptibility to infection noted. The more important results are as follows: 1. Young seedlings were more susceptible to infection than older ones. 2. Seedlings grown under the relatively poor light conditions of winter remained susceptible to infection for a longer time than those grown under the good light conditions of late spring and early summer. 3. Seedlings grown with no external supply of nitrogen remained susceptible to infection for a longer time than seedlings supplied with a complete nutrient solution containing nitrogen. 4. Resistance to infection was accompanied by a deposition of lignin in the cell walls of the tissue surrounding the area of infection. Susceptibility to infection was accompanied by the incompleteness or absence of such cell-wall lignification. It is suggested that such lignification, when continuous, may serve as a barrier in preventing spread of the fungus. 5. Deposition of lignin was found to be a function of living parenchymatous cells and occurred in the vicinity of a wound or fungus infection. In a healthy plant these cells did not become lignified.