Influence of Hormones on Respiratory Metabolism of Healthy & Rust-Affected Tissues

Abstract

The effect of brief (11/2-6 hr) treatments with IAA on the respiratory rates and pathways of healthy bean and wheat leaf tissue and safflower hypocotyl tissue grown under constant environmental conditions were studied. In all species, low concentrations of IAA (1-5 ppm) stimulated rates of respiration while high (100 ppm) inhibited rates. Although alternation of rates was evidence for the penetration of IAA and interaction with cellular metabolic systems, IAA did not appear to alter the pathways of glucose catabolism as measured by C6/C1 ratios. Gibberellic acid, alone or in combination with IAA, also did not influence carbohydrate pathways. Since hormonal effects on growth and metabolism frequently depend on environment and the status of the tissues employed, a number of environmental and biological parameters were tested to ascertain if IAA could induce a change in C6/C1 ratios. No positive effects were observed. IAA failed to induce changes in C6/C1 ratios in tissues infected with rust fungi. It is concluded that the higher levels of IAA in tissues infected with oligate parasites are not involved in the narked increases in oxidative pentose pathways previously observed during sporulation of the parasites.