Background  The land salinization is an important limiting factor for plant introduction and cultivation in some sandy areas in northern China. Cyperus esculentus is an economic crop introduced and cultivated on salinized land in sandy areas in recent years, which has both ecological and economic benefits. However, most domestic and foreign researches on C. esculentus focus on food processing and agricultural production, and there is little research on its resistance mechanism to salt-alkali stress. The purpose of this work simulates the effects of salt and alkali dual-factor cross stress on the growth and physiological processes of C. esculentus, and reveals its salt resistance and tolerance through the exploration of the antioxidant enzyme system activity, osmotic regulation and hormone regulation mechanism of C. esculentus. Alkaline mechanism provides a theoretical basis for the introduction of C. esculentus in the northern saline-alkaline soil.

Methods  Taking the seedlings of C. esculentus as the research object, using the method of potted control, a cross experiment of 3 salt concentration gradients (50-100,150-200, and > 250mmol/L) and 2 pH gradients were set up to explore the effects of different NaCl concentration and pH on the growth and physiological and biochemical characteristics of C. esculentus.

Results  1) Under moderate (150-200mmol/L) and severe stress (>250mmol/L), the growth indexes such as plant height and biomass of C. esculentus were significantly lower than those of the control (P < 0.05), that is, growth was inhibited. Under mild salt stress (<100mmol/L), the effect was not significant; under severe salt stress, pH aggravated the effect of salt stress. 2) The activities of peroxidase and superoxide dismutase in the leaves and roots of C. esculentus increased first and then decreased with the increase of salt concentration.3) The content of osmotic adjustment substances (proline and soluble sugar) in the leaves and roots demonstrated a trend of first increasing and then decreasing with the increase of single salt concentration. Under alkaline conditions, the content of each osmotic adjustment substance increased with the increase of salt concentration. 4) The content of ABA in the leaves increased with the increase of salt stress concentration. The content of ABA in the roots increased with the increase of salt stress concentration until mild salt stress and decreased under the condition with 250mmol/L salt concentration, which may be related to the permanent damage of plant roots caused by severe salt stress.

Conclusions  Salt and alkali stress have an interactive effect on the influence of C. esculentus. C. esculentus presents physiological adaption mechanism to slight and mild saline-alkali stress through antioxidant enzyme system, osmotic regulation and hormone regulation mechanism, while the physiological adaption mechanism would lose its efficiency in severe stress of over 250mmol/L.