Ecophysiologie du stade urédien de Melampsora larici-populina Kleb. et de M. allii-populina Kelb.

Uredospores of Melampsora larici-populina and Melampsora allii-populina show some reactions in common physical factors. In both species germination requires high relative humidity and darkness has adverse effects. For other characters, differences appear in their behavior. The optimum temperature for germination is 13°C for M. larici-populina but 16°C for M allii-populina. M. larici-populina uredospores germinate more slowly but their germ tubes grow faster. Above 16°C, germination of M. laricipopulnaa spores is reduced and temperatures above 30°C induce a delay in subsequent germination. However, their germination capacity is less affected by heavy and long frosts as compared with M. allii populina.