WATER RELATIONS OF LEAVES OF BARLEY INFECTED WITH BROWN RUST

The water balance of brown rust (Puccinia hordei) infected barley seedlings was investigated. It was found that with the progression of the disease, the infected leaves lost their ability to maintain a favourable water status. This was attributed to tears in the cuticle, which occurred from day 5 after infection. In addition, a decreasing responsiveness of leaf diffusion resistance to bulk leaf water content was observed, probably due to the increasing proportion of water loss via the tears in the cuticle. An increase in leaf dry weight per unit area which was not associated with an increase in tissue volume, was found in diseased leaves. These responses to infection were cumulative with disease development, with no sudden effect of sporulation. Leaf turgor and water potentials were found to be lower in diseased leaves than in control leaves. © 1991 Academic Press Limited.