典型热带植物对零度以上低温十分敏感，但机理尚不清楚。
近日，中国科学院西双版纳热带植物园曹坤芳研究组通过模拟零上低温和中等强度光照对4种热带树木光合系统的影响，发现热带植物的光系统II比光系统I对零上低温更敏感，其中一个种光系统I也遭遇严重损伤，低温处理后其光合系统的功能不能恢复，随后叶片死亡脱落。
研究表明，典型的热带植物不能在冬季较冷凉的北热带、亚热带地区正常生长的一个重要的原因是短时间的低温光照胁迫就可能导致其叶片受损严重并死亡。该项研究结果与传统认识相悖，传统研究认为冷敏感植物光系统I比光系统II更敏感。
相关研究成果发表在《光合作用研究》（Photosynthesis Research）期刊上，评审专家认为该论文的发现对于认识热带植物低温敏感性具有重要的意义。(生物谷www.bioon.net)
生物谷推荐原文出处：
Photosynthesis Research DOI：10.1007/s11120-010-9539-7
The different effects of chilling stress under moderate light intensity on photosystem II compared with photosystem I and subsequent recovery in tropical tree species
Wei Huang1, 2 , Shi-Bao Zhang1 and Kun-Fang Cao1, 2
(1) Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, 666303 Mengla, Yunnan, China
(2) School of Life Science, University of Science and Technology of China, 230027 Hefei, Anhui, China
Tropical plants are sensitive to chilling temperatures above zero but it is still unclear whether photosystem I (PSI) or photosystem II (PSII) of tropical plants is mainly affected by chilling temperatures. In this study, the effect of 4°C associated with various light densities on PSII and PSI was studied in the potted seedlings of four tropical evergreen tree species grown in an open field, Khaya ivorensis, Pometia tomentosa, Dalbergia odorifera, and Erythrophleum guineense. After 8 h chilling exposure at the different photosynthetic flux densities of 20, 50, 100, 150 μmol m?2 s?1, the maximum quantum yield of PSII (F v /F m) in all of the four species decreased little, while the quantity of efficient PSI complex (P m) remained stable in all species except E. guineense. However, after chilling exposure under 250 μmol m?2 s?1 for 24 h, F v /F m was severely photoinhibited in all species whereas P m was relative stable in all plants except E. guineense. At the chilling temperature of 4°C, electron transport from PSII to PSI was blocked because of excessive reduction of primary electron acceptor of PSII. F v /F m in these species except E. guineense recovered to ~90% after 8 h recovery in low light, suggesting the dependence of the recovery of PSII on moderate PSI and/or PSII activity. These results suggest that PSII is more sensitive to chilling temperature under the moderate light than PSI in tropical trees, and the photoinhibition of PSII and closure of PSII reaction centers can serve to protect PSI.
