Species-specific responses to drought, salinity and their interactions in Populus euphratica and P. pruinosa seedlings

Abstract

Aims Drought and salinity are severe abiotic stress factors, which limit plant growth and productivity, particularly in desert regions. In this study, we employed two desert poplars, Populus euphratica Oliver and Populus pruinosa Schrenk seedlings, to compare their tolerance to drought, salinity and combined stress. Methods We investigated species-specific responses of P. euphratica and P. pruinosa in growth, photosynthetic capacity and pigment contents, nonstructural carbohydrate concentrations, Cl− allocation, osmotic regulation and the accumulation of reactive oxygen species (ROS) under drought, salinity and the combined stress. Important Findings Populus pruinosa exhibited greater growth inhibitory effects, photosynthesis decline, stomatal closure and ROS accumulation, and lower antioxidant enzyme activities and osmotic regulation compared with P. euphratica under drought, salinity and especially under their combined stress. On the other hand, salt-stressed P. euphratica plants restricted salt transportation from roots to leaves, and allocated more Cl− to coarse roots and less to leaves, whereas salt-stressed P. pruinosa allocated more Cl− to leaves. It was shown that there is species-specific variation in these two desert poplars, and P. pruinosa suffers greater negative effects compared with P. euphratica under drought, salinity and especially under the combined stress. Therefore, in ecological restoration and afforestation efforts, species-specific responses and tolerances of these two poplar species to drought and salinity should be considered under climate change with increasing drought and soil salinity developing.

Combined effects of water stress and salinity on growth, physiological, and biochemical traits in two walnut genotypes

“…δ 13 C) of both walnut trees, but late bearing walnut showed higher δ 13 C under stressful conditions (Figure 3). This result agreed with previous studies showing that water stress and salinity significantly increased WUE (δ 13 C) of plants (Chen et al, 2014; Li et al, 2016; Xu et al, 2008; Yu et al, 2020). The reason may be that water stress and salinity resulted in the stomatal closure (decreased g s ) and increased fixation of 13 C, implying a conservative water use strategy under stressful conditions (Li, 1999; Passioura, 1982).…”

“…In the present study, water stress, salinity, and their combination significantly decreased A , g s , C i , and E of both walnuts (Figure 2A‐D), which is in line with previous studies indicating that such conditions significantly decrease plant growth and gas exchange (Chen et al, 2010; Li et al, 2016; Yu et al, 2020). Furthermore, genotype‐specific stress responses were found as late‐bearing walnut possessed higher A under water stress, salinity and the combined stress.…”

“…Earlier studies have shown that plants can change biomass allocation between roots and shoots to cope with stress, such as water stress and salinity (Brunner et al, 2015; Yu et al, 2020). Our results agree with those studies showing that both walnuts have a higher R/S ratio under stressful conditions (Figure 1E).…”

“…The climate is warm-temperate, dry, and continental. The annual sunshine duration ranges between 2750 and 3029 h, the mean annual rainfall is <50 mm, and mean annual evaporation is >2500 mm (Yu et al, 2020).…”

“…Plants have different physiological and defense responses to lessen the damage under water stress, including changes in morphological and physiological traits to deal with water stress. For example, plants can change biomass allocation between roots and shoots under water‐limited conditions (Brunner et al, 2015; Dong et al, 2016; Yu et al, 2020). Stomatal closure can minimize water loss by transpiration and decrease photosynthesis under water stress (Adams et al, 2013; Chen et al, 2010; Choat et al, 2018).…”