ABSTRACT
The development of food and forage crops that flourish under saline conditions may be a prospective avenue for mitigating the impacts of climate change, both allowing biomass production under conditions of water-deficit and potentially expanding land-use to hitherto non-arable zones. Here, we examine responses of the native halophytic shrub Atriplex leucoclada to salt and drought stress using a factorial design, with four levels of salinity and four drought intensities under the arid conditions. A. leucoclada plants exhibited morphological and physiological adaptation to salt and water stress which had little effect on survival or growth. Under low salinity stress, water stress decreased the root length of A. leucoclada; in contrast, under highly saline conditions root length increased. Plant tissue total nitrogen, phosphorus and potassium content decreased with increasing water stress under low salinity. As salt stress increased, detrimental effects of water deficit diminished. We found that both salt and water stress had increased Na+ and Cl- uptake, with both stresses having an additive and beneficial role in increasing ABA and proline content. We conclude that A. leucoclada accumulates high salt concentrations in its cellular vacuoles as a salinity resistance mechanism; this salt accumulation then becomes conducive to mitigation of water stress. Application of these mechanisms to other crops may improve tolerance and producitivity under salt and water stress, potentially improving food security.
ABSTRACT
In context of the climate change, major abiotic stresses faced by plants include salt stress and drought stress. Though, plants have similar physiological mechanisms to cope with these salt and drought stresses. The physiological and biochemical response of native plants to the combined application of salinity and drought stresses are still not well-understood. Thus, to investigate the combined effect of salinity and drought stresses, an experiment was conducted on Salsola imbricata with four levels of salinity and four drought intensities under the arid climatic conditions. The experiment was conducted in a randomized complete block design with a split-plot arrangement replicated three times. S. imbricata had been found resistant to different levels of individual and combined salt and drought stresses. S. imbricata survived till the end of the experiment. Salt and water stress did not show any significant effects on shoot weight, shoot length, and root length. The drought stress affected the photosynthetic rate, ion uptake and leaf water potential. However, salt stress helped to counter this effect of drought stress. Thus, drought stress did not affect plant growth, photosynthesis rate, and ion uptake when combined with salt stress. Increased Na+ and Cl- uptake under the salt stress helped in osmotic adjustment. Therefore, the leaf water potential (LWP) decreased with increasing the salt stress from 5 dSm-1 until 15 dSm-1 and increased again at 20 dSm-1. At lower salt stress, ABA and proline content declined with increasing the drought stress. However, at higher salt stress, ABA content increased with increasing the drought stress. In conclusion, the salt stress had been found to have a protective role to drought stress for S. imbricata. S. imbricata utilized inorganic ion for osmotic adjustment at lower salinity stress but also accumulate the organic solutes to balance the osmotic pressure of the ions in the vacuole under combined stress conditions. Due to the physical lush green appearance and less maintenance requirements, S. imbricata can be recommended as a native substitute in landscaping under the salt and drought stresses conditions.
ABSTRACT
Tetraena mandavillei L. is a perennial shrub native to the Middle Eastern countries of Asia, which is extensively regarded as a drought-tolerant plant. However, the plant reduces growth and biomass when grown in high concentrations of sodium chloride in the soil. We conducted a pot experiment to influence the negative impact of different levels of salinity (0, 10, and 20 dSm-1 ) and drought stress (100, 80, 60, and 40% water field capacity), to study different growth-related parameters, physiological alterations and ion uptake by T. mandavillei. Both salinity and drought stress caused a negative impact by affecting several attributes of T. mandavillei, but the plants showed some resistance against drought stress conditions in terms of growth and biomass. In addition to that, we noticed that a combinatorial and individual impact of drought and salinity stress decreased photosynthetic pigments and gas exchange parameters in T. mandavillei. Results also depicted that the combination of the abiotic stress conditions drought and salinity induced reactive oxygen species (ROS), indicating that the plants undergo oxidative damaged. However, due to the active plant defense system, the plant enhanced its performance under abiotic stress conditions, but due to the severe drought condition (40% water field capacity), a significant (P < 0.05) decrease in the activities of antioxidant compounds was caused. Furthermore, osmolytes also increased under both salinity and drought stress conditions in this study. Our results also showed that increased salinity and drought stress in the soil caused a significant increase in sodium (Na+ ) and chloride (Cl- ) ions in roots and shoots of T. mandavillei. In contrast to that, the contents of Calcium (Ca2+ ) and potassium (K+ ) were decreased in all organs of the plants with increasing levels of salinity and drought stress. Taken together, T. mandavillei can be classified as a facultative halophyte with the ability to tolerate drought stress and using salt accumulation mechanisms to tolerate salinity stress.
