Variations in osmotic adjustment and water relations of Sphaerophysa kotschyana: Glycine betaine, proline and choline accumulation in response to salinity

Background: Sphaerophysa kotschyana Boiss. is naturally distributed in overly salty regions. The key to the completion of the life cycles of S. kotschyana in harsh saline soils may be hidden in changes of its osmo-protectants, but there is currently no information about the interaction between osmotic adjustment and water relations in adaptation to saline conditions. The aim of this article was to determine growth, relative growth rate (RGR), relative water content (RWC), osmotic potential (psi(Pi)), photosynthetic efficiency (F-v/F-m), thiobarbituric acid-reactive substances (TBARS) and osmo-protectant contents [proline (Pro), choline (Cho) and glycine betaine (GB)] in S. kotschyana leaves and roots exposed to 0, 150 or 300 mM NaCl for 7 and 14 d (days). Results: The results clearly showed that the reductions in growth, RWC, F-v/F-m, RGR and psi(Pi) were more pronounced at 300 mM, especially after 14 d. In the same group, the highest increase in TBARS was recorded in roots (126%) and leaves (31%). The induction at 150 mM was not as high. Therefore, roots appear to be the most vulnerable part of this plant. Moreover, S. kotschyana was able to withstand short-term low salinity. Conclusions: The osmo-protectant accumulation in S. kotschyana as a salinity acclimation or adaptation was sufficient for toleration of low salt concentration (150 mM). In contrast, the plants exposed to the highest NaCl concentration (300 mM) were not able to maintain the ability to prevent water loss because of further decrease in root/shoot ratio of fresh weight (FW) and dry weight (DW), RWC and RGR.