Changes in Osmolarity and Solute Content of Pea Plants Exposed to Salinity and Abscisic Acid

Abstract

The response of pea plants (Pisum sativum L.) to the presence of 192 mM NaCl or of 10^-5 abscisic acid (ABA) was similar: shoot growth was inhibited, internal osmolarity and the content of organic solutes increased, and proline accumulated. It appears that most but not all of the new proline synthesized due to stress is located in the cytoplasmic compartment. The responses of the plant to salinity and externally applied ABA differed, apparently, in the mechanism of adjustment of the internal osmolarity: mainly ion absorption in the first, mainly synthesis of organic osmotica in the second. Potassium might have a special role in controlling internal events in pea shoots. Increase in the internal ABA content may serve as a trigger for the changes in pea shoots, but the sequence of events in pea roots may be different; the trigger may be some mechanism other than ABA accumulation. In this study ABA had no effect on root growth.