Mechanical properties of stem and physiological–biochemical responses of cucumber under different N and K conditions

In order to investigate the effects of N and K on the mechanical properties of cucumber stems, the physiological and biochemical indexes under different N and K conditions were compared. The analysis showed that the pho-tosynthetic rate was affected by both stress and the self-senescence of cucumber plants, and that the crops under N and K stress were stimulated to activate a highly effective antioxidant system to cope with the damage. Sugar, as the basis for the synthesis and structure formation of the stems, was highly related to stem strength, and polyphenol oxidase in the study of stem strength was limited but indispensable. Compared with CK, the epidermal penetration strength under LN, LNLK, and LNHK treatments increased by at least 10%, while the strength under HN, LK, HNLK, and HNHK treatments decreased by at least 7%. To sum up, it was the photosynthesis rate, the sucrose transportation, as well as the futile cycling of K+ that were the keys of stem strength.