Cucumber (Cucumis sativus L.) is one of the most economically important vegetables cultivated worldwide. Cucumbers are typical chilling-sensitive species that are extremely vulnerable to cold stress during solar greenhouse cultivation in winter or early spring in northern China. Under cold stress, cucumbers grow slowly, wither, and even die, thus seriously affecting crop productivity and quality.In the present study, glycine betaine (GB), chitosan (CTS), and chitosan oligosaccharide (COS) were used as exogenous substances to investigate their positive effects in improving cold stress tolerance in cucumber seedlings.
Figure 1. Phenotypic characteristics of cucumber seedlings treated with different exogenous substances under cold stress (12 ◦C/6 ◦C, day/night) after 24 h. NK group represents cucumber seedlings sprayed with distilled water and subjected to normal temperature (28 ◦C/18 ◦C, day/night). LK group represents cucumber seedlings sprayed with distilled water and subjected to cold stress. GB5, GB10, and GB25 groups represent cucumber seedlings sprayed with 5 mM, 10 mM, and 25 mM GB subjected to cold stress, respectively. The COS25, COS50, and COS100 groups represent cucumber seedlings sprayed with 25 mg·L −1 , 50 mg·L −1 , and 100 mg·L −1 COS subjected to cold stress, respectively. The CTS25, CTS50, and CTS100 groups represent cucumber seedlings sprayed with 25 mg·L −1 , 50 mg·L −1 , and 100 mg·L −1 CTS subjected to cold stress, respectively
This study suggests that low-temperature stress significantly affects the morphology, growth, and physiological and biochemical indices of cucumber seedlings. Different concentrations of exogenous GB, CTS, and COS reduced the cold damage state of cucumber seedlings to varying degrees. The alleviation effect of exogenous GB, CTC, and COS on cold stress was concentration-dependent, and 50 mg·L −1 COS showed the best activity. It effectively increases plant growth, chlorophyll content, photosynthetic capacity, osmotic regulatory substance content, and antioxidant enzyme activities while reducing relative electrical conductivity and malondialdehyde levels in cucumber seedlings under cold stress.
Reference:Integrated Physiological and Transcriptomic Analyses Revealed Improved Cold Tolerance in Cucumber (Cucumis sativus L.) by Exogenous Chitosan Oligosaccharide