Abstract:

To explore the response mechanism of maize seedlings to low temperature stress， the low-temperature sensitive GS2264 and the low-temperature tolerant LY2030 were used as materials， which were cultured at 10 （LT） and 22 ℃ （CK） for 7 d. And the changes of seedling growth and photosynthetic performances， reactive oxygen species， osmotic regulation， antioxidant enzymes activities， and the expression levels of antioxidant enzymes related genes in leaves were analyzed. The results showed that low temperature stress inhibited the growth and development of maize seedlings. Compared with CK treatment， the seedling length， root length， seedling fresh weight， root fresh weight， and root-shoot ratio of LT treatment significantly decreased by 7.06%， 19.60%， 18.75%， 24.32% and 7.79%， respectively， and the net photosynthetic rate， stomatal conductance， transpiration rate， rubisco activity， water use efficiency， F_v/F_m and F_v/F_o significantly decreased by 42.88%， 27.09%， 15.23%， 59.38%， 29.78%， 31.90% and 32.88%， respectively， however， intercellular CO₂ concentration， O{}_{\mathrm{2}}^{?-} production rate and the contents of H₂O₂， proline， malondialdehyde significantly increased by 67.27% and 119.55%， 154.04%， 55.19%， the activities of SOD， POD， CAT， APX significantly increased by 46.66%， 96.53%， 158.44%， 4.34%， while GR activity showed a slight decreased of 3.34%. The correlation and principal component analyses showed that a complex and network relationship among traits of maize seedlings. Further analysis showed the relative expression levels of 8 antioxidant oxidase related genes were significantly up-regulated under LT treatment， which indicated they could be used as candidate genes for improving cold resistance in maize. Above results laid a foundation for systematically revealing the cold-resistant response mechanism of maize seedlings and the improvement of cold-resistant maize germplasm.

Key words: maize seedling, low-temperature stress, physiological response, reactive oxygen species, antioxidant enzymes, gene expression level

摘要：

为探究玉米幼苗对低温胁迫的响应机制，以低温敏感型GS2264和耐低温型LY2030玉米幼苗为试材，在10（低温）和22 ℃（对照）处理7 d后测定其幼苗生长、叶片活性氧、渗透调节、抗氧化酶活性、光合性能的变化及抗氧化酶相关基因的表达特征。结果表明，低温胁迫显著抑制玉米幼苗的生长发育。与常温对照相比，低温胁迫下玉米幼苗的苗长、根长、苗鲜重、根鲜重及根冠比分别下降22.98%、31.70%、32.27%、37.40%和7.83%；净光合速率、气孔导度、蒸腾速率、Rubisco活性、水分利用效率、光系统Ⅱ的最大光能转化效率及光系统Ⅱ的潜在光化学活性分别下降42.88%、27.09%、15.23%、59.38%、29.78%、31.90%和32.88%；胞间CO₂浓度升高50.84%；玉米幼苗体内O{}_{\mathrm{2}}^{?-}产生率和H₂O₂、脯氨酸、丙二醛含分别显著升高67.27%和119.55%、154.04%、55.19%；超氧化物歧化酶、过氧化物酶、过氧化氢酶、抗坏血酸过氧化物酶活性增强46.66%、96.53%、158.44%、4.34%，而谷胱甘肽还原酶活性下降3.34%。相关性分析和主成分分析结果表明，22个性状间的关系较为复杂。进一步分析发现，低温胁迫处理下8个抗氧化酶相关基因显著上调表达，因此，这8个基因可作为玉米抗寒性改良的重要候选基因。以上研究结果为低温胁迫下系统揭示玉米幼苗的抗寒响应机制及抗寒种质改良奠定了基础。

关键词: 玉米幼苗, 低温胁迫, 光合性能, 活性氧, 抗氧化酶, 基因表达水平