Response of Wheat Seedlings to Combined Effect of Drought and Salinity

Abstract

In field conditions the plants are most commonly subjected to simultaneous effects of multiple stresses. The mechanisms of plant tolerance to salinity and drought are physiologically connected and overlapping, but some aspects of physiology and metabolism may differ when in the experiment salt and water stress is used separately or both stresses are used simultaneously. Physiological and biochemical reactions of the plants under combined effect of the drought and salinity are unique, which cannot be directly extrapolated from respective responses to each of these stresses individually. Drought and salinity reduce individually the availability of water for plants. However, the presence of salt in the soil inhibits the rate of the development of drought, enabling the plant to survive in unfavorable period of short-term drought without violation of basic physiological functions. At increased NaCl concentration in the soil during the combined stress, basic physiological and biochemical functions of the plants remain constant until a critical threshold, after which the plants' productivity decreases dramatically. This article shows the features of the combined stress and its difference from the drought and salinity individually.

Drought-Adaptive Mechanisms of Young Sweet Cherry Trees in Response to Withholding and Resuming Irrigation Cycles

“…It is clear that P. sargentii increased the SLW under heavy drought to reduce the leaf size, which is advantageous, as it could reduce canopy temperature and improve water use efficiency [41]. The RWC values of MS and SS leaves decreased during the drying cycles as a result of dehydration of the cells, which could have contributed to a relative change in cell volume of leaf tissues [45] and to the maintenance or even decrease in the Ψo values through lower hydration levels [46]. The fact that gs was equal or greater than 100 mmol m −2 s −1 at the most critical moments of the SS strategy (Table 1) supports the evidence that SS leaves did not reach the lower limit of RWC, where tree regulation is deficient, and metabolism is unable to maintain vital functions [47].…”

Changes in the photosynthetic performance, the activity of enzymes of nitrogen metabolism, and proline content in the leaves of wheat plants after exposure to low CO₂ concentration

“…Free Pro accumulates in plants in response to a wide range of abiotic and biotic stresses. Most of the data on the regulation of Pro-metabolism were obtained on plants grown under conditions of salt and osmotic stress (Ivanov 2015). In our experiments with CO2 deficiency, an increase in the Pro concentration in the leaves was also observed (Fig.…”

“…Under unfavorable environmental conditions, the accumulation of proline (Pro) is often observed in plant leaves, the synthesis of which is most often explained by the activation of specific biochemical mechanisms to counteract the harmful effects of stress. We have previously shown that there is a direct correlation between the change in stomatal conductance and the formation of Pro in the leaves of wheat plants (Ivanov 2015). A decrease in CO2 fixation due to stomatal closure under stress conditions also leads to the C/N imbalance and the accumulation of excessive amounts of nitrogen-containing substances, for example, Pro.…”

“…However, the plant response to low CO2 concentration at the physiological and biochemical levels is still insufficiently studied (Wu et al 2020). It has been shown that the oxygen evolution rate remains at a fairly high level, despite a decrease in CO 2 concentration in the intercellular spaces of leaves (Ivanov 2015). On the one hand, under these conditions, there is a change in the ratio of carboxylase and oxygenase activities of ribulose bisphosphate carboxylase/oxygenase (EC 4.1.1.39) and an increase in the photorespiration rate.…”