Eggert Anja, Van Hasselt Philip R, Breeman Anneke M
Department of Marine Biology, University of Groningen, P.O. Box 14, 9750 AA Haren, The Netherlands.
J Plant Physiol. 2003 Aug;160(8):881-91. doi: 10.1078/0176-1617-00810.
Chilling induced inhibition of photosynthesis was studied in nine isolates of the marine tropical to warm-temperate green macrophyte Valonia utricularis (Roth) C. Agardh. According to their temperature requirements for growth and survival, the isolates belong to a cold-tolerant Atlantic/Mediterranean group and a cold-sensitive Indo-west Pacific group. After 5 hours exposure to 5 degrees C under moderate light, all isolates experienced similar substantial photoinhibition, which approached steady state levels after a decline in Fv/Fm to about 40% of the initial values. After return to optimal temperature and dim light conditions, Fv/Fm values increased with biphasic kinetics. A fast phase with half-life times of less than 30 minutes (dynamic photoinhibition) was followed by a slow phase lasting a few hours, indicating repair of photodamaged PSII reaction centres (chronic photoinhibition). In the Atlantic/Mediterranean isolates the fast phase accounted for more than 80 % of the recovery response, showing that these isolates were able to cope with the applied low temperature stress by down-regulating their PSII reaction centres. In contrast, the two isolates from the Seychelles were predominantly photodamaged. In a second experiment, three isolates (Corsica, Seychelles, Japan) were exposed to a similar relative amount of cold stress (0, 10, 15 degrees C, respectively). The Japanese isolate and the isolate from the Seychelles showed significantly less inhibition compared to 5 degrees C exposure, but no significant difference was found in the Corsican isolate. However, the degree of low temperature stress had no significant influence on the relative contributions of dynamic and chronic photoinhibition. Only two of the seven investigated isolates had a lower final inhibition level when grown at sub-optimal temperatures than at optimal temperatures. However, all sub-optimally grown Atlantic/Mediterranean isolates exhibited faster recovery kinetics from chilling-induced photoinhibition than optimally grown plants. This is related to a faster recovery from chronic photoinhibition than to a higher relative contribution of dynamic photoinhibition. A specific role of the photoprotective pigments of the xanthophyll cycle, leading to an acclimation response in the Atlantic/Mediterranean isolates may be involved. We conclude that ecotypic differentiation in V. utricularis is mirrored in different degrees of susceptibility to low temperature stress.
对9个海洋热带至暖温带绿藻大叶藻（Valonia utricularis (Roth) C. Agardh）分离株进行了低温诱导光合作用抑制的研究。根据它们生长和存活的温度需求，这些分离株分为耐寒的大西洋/地中海组和冷敏感的印度-西太平洋组。在中等光照下暴露于5℃ 5小时后，所有分离株都经历了相似程度的显著光抑制，在Fv/Fm下降至初始值的约40%后接近稳态水平。回到最适温度和弱光条件后，Fv/Fm值以双相动力学增加。先是半衰期小于30分钟的快速阶段（动态光抑制），随后是持续数小时的缓慢阶段，表明光损伤的PSII反应中心得到修复（慢性光抑制）。在大西洋/地中海分离株中，快速阶段占恢复反应的80%以上，表明这些分离株能够通过下调其PSII反应中心来应对施加的低温胁迫。相比之下，来自塞舌尔的两个分离株主要受到光损伤。在第二个实验中，三个分离株（科西嘉岛、塞舌尔、日本）分别暴露于相似相对量的冷胁迫（分别为0℃、10℃、15℃）。与暴露于5℃相比，日本分离株和来自塞舌尔的分离株的抑制作用明显较小，但科西嘉岛分离株未发现显著差异。然而，低温胁迫程度对动态和慢性光抑制的相对贡献没有显著影响。在七个研究的分离株中，只有两个在次优温度下生长时的最终抑制水平低于在最适温度下生长时。然而，所有次优生长的大西洋/地中海分离株从低温诱导的光抑制中恢复的动力学比最优生长的植物更快。这与慢性光抑制的更快恢复有关，而不是与动态光抑制的更高相对贡献有关。叶黄素循环的光保护色素的特定作用可能导致大西洋/地中海分离株的适应反应。我们得出结论，大叶藻的生态型分化反映在对低温胁迫的不同敏感程度上。
