PEP-Carboxylase Activity: A Comparison of its Role in a C4 and a C3 Species Under Salt Stress.

In our experiments, we found an increase of PEP-carboxylase activity in young shoots of maize under salt stress. Within this study, several analyses were carried out to identify the function of this enhanced enzyme activity during salt stress. In our first experiment, we analysed plants of the salt-resistant maize hybrid SR 03 ( Zea mays L .), whereas in the second experiment, we compared maize and wheat ( Triticum aestivum L. cv. Thasos), which were grown under two different light intensities for 20 days. In the saline treatments, NaCl was applied up to 100 mm, while control plants grew under non-saline conditions (1 mm NaCl). Analyses of shoot fresh weight revealed a comparable reduction for both genotypes and suggested salt resistance at a similar level. Analyses of sugar concentrations showed an increase in the saline treatment for both genotypes independent of the light intensity. Results for sucrose concentrations led to the conclusion that an increase in PEP-carboxylase activity was not required for sugar metabolism. Independent of light intensity, alkalinity and malate concentrations were decreased only in wheat. It can be concluded that an enhancement of PEP-carboxylase activity in young shoots of maize supports organic acid metabolism under salt stress. [ABSTRACT FROM AUTHOR]