Smog Injury and Rust Infection.

Abstract

Bean and sunflower leaves infected with rust (Uromyces phaseoli or Pucclnia helianthi) were less injured by natural or artificial smog than were otherwise similar, healthy leaves. To produce the same degree of smog, or ozonated olefin, damage on bean tissue that had been infected with rust for 7 days required about 5 times as long an exposure to smog as to produce the same injury in healthy tissues. Rusted tissue in which the rust mycelium was killed by heat was still resistant to smog damage. The protection from smog damage by rust infection could not be explained by stomatal closure or by the high content of pantothenic acid in the rust infected tissue but appears to be due to some substance that diffuses beyond the limits of the rust mycelium.