ANTIOXIDANT COMPOUND RESPONSES TO CHILLING STRESS IN DIFFERENTIALLY SENSITIVE INBRED MAIZE LINES

Chilling temperatures increase the amounts of potentially lethal toxic oxygen compounds present within plants. These toxic oxygen compounds can be scavenged by antioxidant compounds such as ascorbate and beta-c arotene. Three developmental stages (first, third and fifth leaf) of f our inbred lines of maize (Zea mays L.) exhibiting differential sensit ivity to chilling were examined in order to determine if the chilling- sensitive line had lower concentrations of antioxidant compounds than did the tolerant lines. Plants were exposed to one of three treatments : (1) control (25 degrees C constant), (2) control treatment plus a sh ort-term chilling exposure of 11 degrees C one day prior to harvesting , and (3) long-term (11 degrees C constant) chilling exposure. Total a scorbate, total glutathione, beta-carotene, alpha-tocopherol and chlor ophyll contents were quantified, and ratios of dehydroascorbate/ascorb ate and reduced/oxidized glutathione were determined. Lower concentrat ions of beta-carotene were found in the chilling-sensitive relative to those in the chilling-tolerant lines for the first-leaf stage under b oth short- and long-term chilling treatments. Concentrations of total ascorbate and glutathione and beta-carotene in the chilling-sensitive line increased as the chilling treatment progressed and as the plants developed until they ultimately became either significantly higher or no different relative to the tolerant lines. Results suggest that this sensitive line became less sensitive to chilling-induced oxidative st ress with development.