Leaf physiological characteristics of seedlings of three Atriplex species under NaCl stress.

Atriplex species, such as Atriplex canescens ssp. aptera, A. canescens ssp. canescens var. laciniata and A. canescens, as unique quasi-evergreen shrubs in arid and semi-arid desert area, are of high socio-ecological importance in controlling desertification, improving soil quality in saline land, and supporting local ecological balance. Here we measured salt injury index, salt-tolerant thresholds and physiological characteristics of the first-year seedlings by a salt-stress experiment conducted in pots. In the experiment, the pots were filled with sand and the six salt levels were adjusted to 0, 0.1%, 0.3%, 0.5%, 0.7%, and 1.0% NaCl. The results showed that: 1) Na+ increased and K+ decreased in each part of three Atriplex seedlings under salt stress. Compared with A. canescens ssp. aptera and A. canescens, the relatively lower Na+ and higher K+ contents were retained in each part of A. canescens ssp. canescens var. laciniata, which was conducive to keeping higher K+/Na+ balance. 2) The initial NaCl concentration with salt stress, salt-tolerance threshold and salt concentration limit of A. canescens ssp. canescens var. laciniata were higher than the other two plants. 3) The salt-tolerance thresholds of A. canescens ssp. aptera, A. canescens ssp. canescens var. laciniata and A. canescens were 0.59%, 0.68%, and 0.63%, respectively. 4) With salt stress increasing, MDA content and cytomembrane permeability were consistently increasing. 5) The salt-tolerance thresholds of the three species based on subordinate function comprehensive evaluation were in the order of A. canescens ssp. canescens var. laciniata (0.686)＞A. canescens (0.532)＞A. canescens ssp. aptera (0.102). It is suggested that A. canescens ssp. canescens var. laciniata has a stronger adaptability to saline soil than A. canescens and A. canescens ssp. aptera.