Photosynthesis in Healthy and Rust-Affected Plants

Abstract

Incorporation of C/sup 14/O/sub 2/ during photosynthesis has been studied in healthy and rust-affected plants of bean, wheat, and safflower. Bean leaves carrying relatively light infection intensities showed consistent stimulation durin the flecking period when symptoms were first apparent. Subsequently, rate of C/sup 14/O/sub 2/ incorporation declined to one-third or one-half the rates of normal leaves. Heavily infected primary bean leaves did not show stimulation at any time, but did exhibit an abrupt decline in C/sup 14/O/sub 2/ fixation once sporulation was apparent. Wheat leaves infected by the stem rust fungus also showed marked inhibition during fungus sporulation, but there was no positive evidence for stimulated rates at any level of infection. Marked stimulation was found in young trifoliate leaves during periods when infected unifoliate leaves were inhibited. The extent of stimulation appeared to be related to the infection intensity of inoculated primary leaves. The data suggest that inhibition of photosynthesis in infected tissue can be compensated at least partially by stimulation in organs at a distance from the infected leaf. 25 references, 4 figures, 5 tables.