Chloride is beneficial for growth of the xerophyte Pugionium cornutum by enhancing osmotic adjustment capacity under salt and drought stresses.

Chloride (Cl-) is pervasive in saline soils, and the existing research concerning the influence of Cl- on plants has mainly focused on its role as an essential micronutrient and its toxicity when massive accumulations occur. However, the possible functions of Cl- in plants adapting to abiotic stresses have not been well documented. Previous investigations have shown that the salt tolerance of the xerophytic species Pugionium cornutum might be related to high Cl- accumulation. Here, we further investigated the Cl--tolerant characteristics and possible physiological functions of Cl- in the salt tolerance and drought resistance of P. cornutum. The results showed that P. cornutum can accumulate a large amount of Cl- in its shoots, facilitating osmotic adjustment and turgor generation under saline conditions. The application of DIDS, a blocker of anion channels, significantly inhibited Cl- uptake, decreased both the Cl- content and the contribution of Cl- to leaf osmotic adjustment, and therefore exacerbated the NaCl-induced growth inhibition of P. cornutum. Unlike glycophytes, P. cornutum could maintain NO3- homeostasis in its shoots when large amounts of Cl- were absorbed and accumulated. The addition of NaCl mitigated the deleterious effects of osmotic stress on P. cornutum because Cl- accumulation elicited strong osmotic adjustment capacity. These findings suggest that P. cornutum is a Cl--tolerant species that can absorb and accumulate Cl- to improve growth under salt and drought stresses.