关键词: 中国南瓜, 低温胁迫, 生理指标, 光合作用

Abstract: Taking 2 low-temperature tolerant and 2 low-temperature sensitive Cucurbita moschata Duch. seedlings as test materials,this experiment conducted low-temperature stress treatment：with day and night 10 ℃/2 ℃（12 h/12 h）in an artificial climate chamber；took day and night 25 ℃/15 ℃（12 h/12 h）as a
normal temperature contrast；and studied the effects of low-temperature stress on physiological indexes and photosynthetic related indexes of Cucurbita moschata seedlings with different low temperature tolerance．The results indicated that when low-temperature stress sustained 10 days，the soluble sugar content in low-temperature tolerant germplasm resources was still obviousely higher than that in low-temperature sensitive germplasm resources．While，after low-temperature stress，there were no obviouse differences among soluble protein content in low-temperature tolerant germplasm resources and low-temperature sensitive germplasm resources．The low-temperature tolerant germplasm resources could better maintain the chlorophyll content in leaves，and
its net photosynthetic rate was signifigantly higher than that in low-temperature sensitive germplasm resources．Correlation analysis showed that Fv/Fm was significantly positively correlated with Fv/F0 and negatively correlated with stomatal conductance．The net photosynthetic rate，chlorophyll content and soluble sugar content showed significant or extremely significant positive correlation．The above results indicated that the soluble sugar content，chlorophyll content and net photosynthetic rate could be used as reliable indexes to identify the lowtemperature tolerance of Cucurbita moschata germplasm resources under low temperature stress for 7 days．

Key words: Cucurbita moschata Duch., low-temperature stress, physiological index, photosynthesis