Calcium carbide induced ethylene modulate biochemical profile of Cucumis sativus at seed germination stage to alleviate salt stress

• Salt stress inhibits seed germination and physiology of cucumber.
• Calcium carbide (CaC2) induced ethylene may alter biochemical profile of cucumber.
• Ethylene perception and synthesis inhibitor reduced positive impact of CaC2.
• CaC2 increased sugars, proteins and antioxidant activities in salt stress.
• Decreased melondialdehyde contents in salt stress confferred positive role of CaC2..

Ethylene is a hormone, which is well known for inducing triple responses in seedling with additional benefit to induce seed germination. However, its direct application to plants is prohibited owing to its gaseous nature and cost, thereby its precursor such as ethephon, 1-aminocyclopropane-1-carboxylate and calcium carbide (CaC2) could be applied. In this study, in vitro experiments were conducted with the aim to determine CaC2 ability to induce ethylene production and antioxidant activity for salt stress alleviation in cucumber at seed germination stage. Seeds were treated with various NaCl solution concentrations in the presence and absence of CaC2. The germination rate and ethylene evolution from seeds were reduced gradually with increasing NaCl concentrations and severely inhibited at 200 mM NaCl solution concentration. Addition of CaC2 in incubation medium significantly alleviated inhibitory effects of salt, however, addition of antagonists of ethylene perception (AgNO3) and ethylene synthesis (CoCl2) reduced positive impact of CaC2 on germination. At 150 mM NaCl and 30 mg CaC2 plate−1 significantly increased the activities of α-amylase, superoxide dismutase, catalase, soluble sugars, free amino acids and protein contents while decreased hydrogen peroxide (H2O2) and malondialdehyde (MDA) compared to that where NaCl was applied alone. Increased seed germination while decreased MDA and H2O2 contents under salt stress revealed the ameliorative impact of CaC2, which is possibly due to increased ethylene production and antioxidant activity. It is concluded that exogenously applied CaC2 might be used as an effective ethylene analogue in alleviating the salinity induced germination inhibition of cucumber seeds.