Salt stress induces Kranz anatomy and expression of C photosynthetic enzymes in the amphibious sedge Eleocharis vivipara.

Eleocharis vivipara Link is a unique amphibious leafless plant of the Cyperaceae. The terrestrial form develops culms with Kranz anatomy and C-like traits, while the submerged form does culms with non-Kranz anatomy and C traits. The submerged form develops new culms with C-like mode when exposed to air or exogenous abscisic acid. In this study, we investigated whether salt stress (0.05-0.3 M NaCl) has a similar effect. When the submerged form was grown for one month in solutions of 0.1 M NaCl and more, culm growth was strongly suppressed. However, these plants slowly developed new culms that had Kranz anatomy with chloroplast-abundant Kranz bundle sheath cells. Although the culms of the submerged form had only few stomata, culms grown in the NaCl solution had many stomata. The NaCl-grown culms also accumulated large amounts of C photosynthetic enzymes (phosphoenolpyruvate carboxylase and pyruvate Pi dikinase), and the cellular localization patterns of these enzymes and ribulose 1,5-bisphosphate carboxylase/oxygenase were similar to those in terrestrial culms. Accumulation of C enzymes increased in mature culms of the submerged form (with non-Kranz anatomy) when exposed to 0.2 M NaCl solution for one week. These results suggest that salt stress induces development of Kranz anatomy and expression of C photosynthetic enzymes in the submerged C form of E. vivipara, whereas the anatomical and biochemical traits of C photosynthesis appear to be regulated independently.