Abstract
Drought and salinity are the two major abiotic stresses constraining the crop yield worldwide. Both of them trigger cellular dehydration and cause osmotic stress which leads to cytosolic and vacuolar volume reduction. However, whether plants share a similar tolerance mechanism in response to these two stresses under natural conditions has seldom been comparatively reported. There are three different ecotypes of reed within a 5 km2 region in the Badanjilin desert of Northwest China. Taking the typical swamp reed (SR) as a control, we performed a comparative study on the adaption mechanisms of the two terrestrial ecotypes: dune reed (DR) and heavy salt meadow reed (HSMR) by physiological and proteomic approaches coupled with bioinformatic analysis. The results showed that HSMR and DR have evolved C4-like photosynthetic and anatomical characteristics, such as the increased bundle sheath cells (BSCs) and chloroplasts in BSCs, higher density of veins, and lower density and aperture of stomata. In addition, the thylakoid membrane fluidity also plays an important role in their higher drought and salinity tolerance capability. The proteomic results further demonstrated that HSMR and DR facilitated the regulation of proteins associated with photosynthesis and energy metabolism, lipid metabolism, transcription and translation, and stress responses to well-adapt to the drought and salinity conditions. Overall, our results demonstrated that HSMR and DR shaped a similar adaption strategy from the structural and physiological levels to the molecular scale to ensure functionality in a harsh environment.
Highlights
Drought and salinity are the two major abiotic stresses affecting plant growth and constraining agriculture productivity because of their inhibitory effects on many physiological processes
32.6 16.72 18.37 62.34 0.09 1.36 2.13 25.15 the typical swamp reed (SR) growing in the swamp with water-saturated soil and a 0.17% salt content in the root zone, the two terrestrial ecotypes (HSMR and dune reed (DR)) showed distinct differences in water and salt contents in the soil of the root zone, of which the heavy salt meadow reed (HSMR) growing on the low-lying salt flats had 43.53% water content and the highest salt content (0.86%) in the root zone, while the DR distributing on the 10 m high dune possessed the lowest water (18.37%) and salt contents (0.09%) in the root zone (Table 1)
The net photosynthetic rate (Pn) measured around 10∼11 a.m. was the highest in SR, followed by HSMR, and the lowest in the DR, which were closely related to their respective stomatal conductance (Gs) and intercellular CO2 concentration (Ci) (Figures 1D–F)
Summary
Drought and salinity are the two major abiotic stresses affecting plant growth and constraining agriculture productivity because of their inhibitory effects on many physiological processes. A variety of evidence indicates that combined stress factors impact plant growth and development more severely than a single one (Pandey et al, 2017; Sengupta et al, 2021). Under natural conditions, stresses tend to develop gradually and progressively, and plant responses might be dramatically different from those abrupt stress treatments. The studies applied a single stress factor to help researchers to identify specific genes or/and proteins linked to the stress, but might not be able to illustrate the complex mechanism of plant responses to the multifactorial stress in natural conditions. It is necessary to comprehensively understand the response mechanisms formed in the adaption of plants to variable, multifaceted, and usually stressful natural conditions
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