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

摘要： 以2份耐低温和2份低温敏感的中国南瓜幼苗为试材，在人工气候室中进行昼/夜为10 ℃/2 ℃（12 h/12 h）的低温胁迫处理，以昼/夜为25 ℃/15 ℃（12 h/12 h）作为常温对照，研究低温胁迫对不同耐低温性中国南瓜幼苗生理指标和光合作用相关指标的影响。结果表明：低温胁迫10d时，耐低温种质的可溶性糖含量仍明显高于低温敏感种质；而低温胁迫后的可溶性蛋白含量在耐低温种质与低温敏感种质间无明显差异；耐低温种质能够在低温胁迫下更好的维持叶片叶绿素含量，且净光合速率明显高于低温敏感种质。相关性分析表明，Fv/Fm与Fv/F0呈显著正相关，与气孔导度呈显著负相关；净光合速率、叶绿素含量和可溶性糖含量之间均表现为显著或极显著的正相关关系。以上结果表明，低温胁迫7 d时，可溶性糖含量、叶绿素含量和净光合速率可以作为中国南瓜种质耐低温性鉴定的可靠指标。

关键词: 中国南瓜, 低温胁迫, 生理指标, 光合作用