Changes of Chlorophyll Fluorescence Parameters and Correlations Between Variety Tolerance in Pumpkin Seedlings Under Chilling and Low Irradiance Conditions
In order to elucidate the cultivar tolerance of pumkin plants to chilling under low irradiance, five Lines of pumpkin (Cucurbita moschata) plants were exposed to chilling under low irradiance (12℃/8℃ ,80 μmol·m-2 ·s-1) for 6 d, and then chilling index, gas exchanges, chlorophyll fluorescence parameters and antioxidant enzyme activities were investigated.Results showed that the chilling index was increased evidently by low temperature under low irradiance treatment, and it was less significantly in line S4-1 and S44-1 than line G2-3, G75-1 and G75-2, suggesting that line S4-1 and S44-1 were more tolerant.Chilling under low irradiance treatment resulted in the decrease in net photosynthesis rate (Pn), coefficient of photochemical quenching (qP), effective quantum use efficiency of PSII in the light-adapted state (Fv'/Fm') and actual quantum yield of PSII (IPSI).Line S4-1 and S44-1 showed less evidence of these parameters compared with other lines.MDA content and electrolyte leakage were increased by chilling under low irradiance, and were less significantly in Line S4-1 and S44-1 plants.The activities of SOD, CAT and GPOD increased firstly and then decreased during the chilling under low irradiance treatment, while APX activities showed the opposite trend.Pn, qP, Fv'/Fm' and IPSI were negatively correlated to chilling index, while MDA content and electrolyte leakage were positively correlated to chilling index.Thus these parameters can be used to identify the cultivar tolerance of pumkin plants to chilling under low irradiance.The present study could provide theoretical basis for selection chilling and low irradiance resistant varieties in pumpkin.
chilling and low irradiancepumpkinchlorophyll fluorescenceantioxidant enzyme
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