三种常绿阔叶树光系统Ⅱ在低温胁迫下的光抑制及恢复

Photoinhibition and recovery of photosystem Ⅱ of three broad-leaved evergreens under low temperature stress

关键词:  光合作用生理, 光系统Ⅱ, 光抑制, 低温胁迫, 非光化学淬灭, 光保护

Key words:  physiology of photosynthesis, photosystem Ⅱ(PS Ⅱ), photoinhibition, low temperature stress, non-photochemical quenching(NPQ), photoprotection

摘要:

冬季低温胁迫对亚热带常绿阔叶树光合活性的主要影响之一,体现在光合机构的低温光抑制。为了阐明冬季低温胁迫下常绿阔叶树光系统Ⅱ的光抑制程度及光保护机制,该文研究了冬季自然低温胁迫(零下低温冻害和零上低温寒害)对红叶石楠、枇杷和猴樟三种亚热带常绿阔叶树光合机构光系统Ⅱ(PSⅡ)光抑制的影响以及春季气温回暖后的恢复情况。结果表明:冻害和寒害低温胁迫使猴樟的PSⅡ活性显著降低,PSⅡ受到较严重的光抑制,低温胁迫解除后PSⅡ活性未能完全恢复。红叶石楠PSⅡ活性下降程度和光抑制程度最轻,春季PSⅡ活性显著上升,光抑制显著下降。枇杷PSⅡ活性和光抑制程度介于猴樟和红叶石楠之间。低温胁迫下红叶石楠的非光化学猝灭(NPQ)接近常温水平; 枇杷的NPQ略有降低,春季恢复正常; 猴樟NPQ最低,春季低温解除后仍不能完全恢复。此外,三种常绿阔叶树在冬季低温胁迫和春季恢复时期的NPQ与PSⅡ的光抑制程度存在显著的负相关关系。综合以上结果分析表明,冬季低温对红叶石楠PSⅡ影响不大,对枇杷有一定影响但春季气温回暖后可以及时恢复,对猴樟PSⅡ有显著的光抑制且恢复过程较慢,同时NPQ对保护常绿阔叶树PSⅡ免受冬季低温光抑制有重要的贡献。

Abstract:

The limits on photosynthesis of subtropical evergreen trees imposed by winter low temperature are mainly from photoinhibition of photosynthetic apparatus. To understand the extent of photoinhibition of photosystem Ⅱ(PS Ⅱ)and the mechanism of photoprotection of evergreen trees under winter low temperature stress, PS Ⅱ photoinhibition and recovery were studied in three broad-leaved evergreen tree species Photinia × fraseri, Eriobotrya japonica and Cinnamomum bodinieri. The results were as follows: PS Ⅱ of Cinnamomum bodinieri was severely depressed and suffered photoinhibition under freezing and chilling temperature, and function of PS Ⅱ was unable to fully recover at spring normal temperature. Photinia × fraseri showed the most unaffected PS Ⅱ function and the least photoinhibition, whereas the situation in Eriobotrya japonica was in the intermediate. Accordingly, Photinia × fraseri maintained the level of non-photochemical quenching(NPQ)almost as high as at normal temperature, and NPQ of Eriobotrya japonica showed a little decrease but recovered at normal temperature condition. Cinnamomum bodinieri displayed the lowest NPQ under low temperature and was unable to totally recover. Furthermore, all the three tree species showed a strong negative relationship between NPQ and PS Ⅱ photoinhibition, which was indicated by the maximum potential photochemical efficiency of PS Ⅱ(F_v/F_m)and the quantum yield of non-regulated energy dissipation of PS Ⅱ [Y(NO)]. Overall, the results demonstrate that Photinia × fraseri is more resistant to low temperature stress than Eriobotrya japonica and Cinnamomum bodinieri in terms of PS Ⅱ. At the same time, NPQ plays an important role for protecting PS Ⅱ of these trees from photoinhibition under low temperature.