Abstract: In order to compare the regulatory effects of different oligosaccharides on the growth and yield of greenhouse cucumber, the chitosan oligosaccharide(GT) and mixed-oligosaccharide(KP) were selected as the preparation treatments, while the conventional control(CG) and clear water control(CK) were compared as controls. The relative leaf chlorophyll content(SPAD), chlorophyll fluorescence parameters, leaf cell structure, root morphologies and root vigor(RV), antioxidant enzyme activity and endogenous hormone contents were all tested in this study. The results showed that KP treatment could effectively promote the growth and development of cucumber leaves and roots. Compared with the other treatments, the SPAD, maximum photochemical quantum yield(Fv/Fm), photochemical quenching coefficient(qP), non-photochemical quenching coefficient(NPQ) and RV of the KP treatment were all significantly increased by 4.15%-15.63%, 6.49%-20.03%, 33.33%-152.63%, 10.37%-71.62% and 8.51%-171.43%. Meanwhile, the superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) activities were significantly increased by 6.75%-91.49%, 3.85%-97.62% and 3.00%-28.15%; the IAA content of cucumber leaves were enhanced larger than 5.43% in the late growth stage, and the abscisic acid (ABA) content decreased by 4.35%-18.63%. The yield and soluble sugar content of the KP treatment were increased by 13.72% and 11.52%, respectively. For the GT treatment, unstable effects were obtained, including the root and crown growth, endogenous hormones and antioxidant enzyme activity. The photosynthetic physiological characteristics of leaves, such as SPAD, chlorophyll fluorescence parameters and leaf ultrastructure, and RV in the fruit set stage were improved slightly. Compared with GT, KP showed a clear advantage in promoting coordinated root and crown growth, regulating antioxidant enzyme activity, and balancing the cucumber's endogenous hormones. The correlation analysis results showed that the yield of cucumber was significantly positively correlated with NPQ, RV, SOD and POD activity(P<0.01), and positively correlated with Fv/Fm(P<0.05). While SOD and POD were negatively correlated with ABA content(P<0.05). In conclusion, exogenous mixed-oligosaccharides mainly promoted the coordinated growth of root and shoot, especially maintained the high photosynthesis efficiency, root vitality and the stability of leaf functional structure in the late growth period, regulated the activity of antioxidant enzymes and the balance between growth promoting hormone and growth inhibiting hormone, which lead to the stability of cell membrane function in the late growth period, delay natural aging of leaves, and the improvement of yield and quality of cucumber.

Key words: Greenhouse cucumber, Mixed-oligosaccharides, Chitosan oligosaccharide, Physiological characteristics, Yield, Quality