ABSTRACT:
The tumescent stems of Zizania latifolia are consumed as vegetable in southern and eastern Asia. This study aimed to compare photosynthesis and chilling tolerance parameters between two well-known Zizania latifolia cultivars: Longjiao 2 and Zhejiao 911, which are chilling tolerant and sensitive, respectively. We found that severe cold stress induced photosynthesis inhibition (5°C) resulted from non-stomatal factors. However, net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) of the cultivar Longjiao 2 were higher than that of Zhejiao 911 with more gradual variations. Six parameters of chlorophyll fluorescence including latent activity of PSII (Fv/F0), efficiency of primary photochemistry (Fv/Fm), photochemical quenching coefficient (qP), non-photochemical quenching coefficient (qN), quantum yield of electric transport (Yield) and the ratio of electric transport at PSII (ETR) were analyzed in the two cultivars. We found that Longjiao 2 had significantly higher Fv/Fm and qN than Zhejiao 911 while qP values were only slightly different for the two lines at severe cold stress. In our experiments, Yield and ETR changed in a similar way in both Longjiao 2 and Zhejiao 911. In addition, the ability of heat dissipation of Longjiao 2 was statistically higher than that found in Zhejiao 911 when treated at 5°C for one day. These data suggest that cultivar Longjiao 2 induces chilling tolerance by modulating critical pathways including photosynthesis and energy dissipation.
Keywords:
Longjiao 2; Zhejiao 911; cold stress; photosystem; photoinhibition.
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