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| 胡杨异形叶光合作用对光强与CO2浓度的响应 | |
| 引用本文： | 王海珍,韩路,徐雅丽,牛建龙. 胡杨异形叶光合作用对光强与CO2浓度的响应[J]. 植物生态学报, 2014, 38(10): 1099-1109. DOI: 10.3724/SP.J.1258.2014.00104 |
| 作者姓名： | 王海珍 韩路 徐雅丽 牛建龙 |
| 作者单位： | 塔里木大学植物科学学院, 新疆生产建设兵团塔里木盆地生物资源保护利用重点实验室, 新疆阿拉尔 843300 |
| 基金项目： | 塔里木荒漠河岸林建群种适应土壤干旱的用水策略与机理研究;胡杨叶形可塑性与生理生态适应机理研究 |
| 摘 要： | 胡杨(Populus euphratica)叶形多变, 随个体生长发育, 植株出现条形、卵形和锯齿阔卵形叶。在新疆塔里木河上游人工胡杨林内选择具有此3种叶形的成年标准株, 将枝条拉至同一高度, 通过活体测定, 比较其光合作用-光与CO2响应及叶绿素荧光响应特征。结果表明: 胡杨异形叶光合速率对光强/CO2浓度与电子传递速率对光强的响应曲线均可用直角双曲线修正模型来拟合, 得出的主要光合参数与实测值较吻合。胡杨卵形叶、锯齿阔卵形叶光合速率-光响应参数与生化参数及快速光响应参数与条形叶差异显著, 而光合速率-CO2响应参数则无显著差异。胡杨异形叶CO2饱和浓度下的最大净光合速率(Pnmax)较饱和光强下的Pnmax高, 表明胡杨强光下光合速率在很大程度上受CO2供应和1,5-二磷酸核酮糖(RuBP)再生能力的限制。卵形叶、锯齿阔卵形叶的初始量子效率(α)、初始羧化效率(CE)、Pnmax、光合能力(Amax)与最大羧化速率(Vcmax)均显著高于条形叶; 锯齿叶光饱和点(LSP)、最大电子传递速率(ETRmax)与光呼吸速率(Rp)高于卵形叶, 条形叶光补偿点(LCP)与LSP、α、CE最低。表明荒漠干旱环境下胡杨锯齿叶最耐强光, 高Rp可能是其耗散过剩光能、保护光合机构免于强光破坏的重要途径; 卵形叶高的α、CE、磷酸丙糖利用效率(TPU)、PSII实际光化学效率(ΦPSII)与低LCP及叶氮分配策略是其保持高光合速率的原因; 条形叶ΦPSII、ETR、Pn低, 因其制造光合产物不足而难以满足树体生长逐渐减少并处于树冠下部。可见, 胡杨条形叶光合效率低、抗逆性差, 主要以维持生长为主; 随着树体长大, 条形叶难以适应荒漠环境来维系其生长, 出现了卵形叶; 卵形叶光合效率高, 易于快速积累光合产物而加快树体生长, 但其LSP低和耐光抑制能力弱, 逐渐被更耐强光、高温与大气干旱的锯齿叶所取代, 从而使胡杨在极端逆境下得以生存, 这是胡杨从幼苗到成年叶形变化及异形叶着生在树冠不同高度的原因。 |
| 关 键 词： | 适应机制 异形叶 光合作用 胡杨 响应参数 |
| 收稿时间： | 2014-05-30 |
| 修稿时间： | 2014-07-13 |
Photosynthetic responses of the heteromorphic leaves in Populus euphratica to light intensity and CO2 concentration |
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| WANG Hai-Zhen,HAN Lu,XU Ya-Li,NIU Jian-Long. Photosynthetic responses of the heteromorphic leaves in Populus euphratica to light intensity and CO2 concentration[J]. Acta Phytoecologica Sinica, 2014, 38(10): 1099-1109. DOI: 10.3724/SP.J.1258.2014.00104 | |
| Authors: | WANG Hai-Zhen HAN Lu XU Ya-Li NIU Jian-Long |
| Affiliation: | College of Plant Science, Tarim University, Key Laboratory of Protection and Utilization of Biological Resource in Tarim Basin, Xinjiang Production & Construction Groups, Alar, Xinjiang 843300, China |
| Abstract: | Aims Populus euphratica is an important tree species and its leaf shape changes along the growth stages. Adult trees commonly comprise polymorphic leaves, including lanceolate, oval and serrated broad-oval leaves. Our objective were to elucidate the ecophysiological mechanisms of P. euphratica adapting to high temperature and strong light environment and its survival strategy by comparing photosynthetic efficiency and chlorophyll fluorescence parameters in heteromorphic leaves in an extremely arid desert area, and to explore the causes of changes in leaf shape in P. euphratica, in order to provide a scientific basis for the protection of desert P. euphratica forests. Methods Individuals with 10 cm diameter at breast height from a planted P. euphratica forest were selected. Measurements were made on the parameters of gas changes and chlorophyll fluorescence of three different leaf shapes on branches at the similar height using a LI-6400 Portable Photosynthesis System and a PAM-2100 chlorophyll fluorometer. The light/CO2 response curves of net photosynthetic rate (Pn) and rapid light curves of chlorophyll fluorescence in heteromorphic leaves were fitted and analyzed. Important findings The light and CO2 response curves, rapid light curves of the three different leaf shapes in P. euphratica were better fitted by the modified rectangular hyperbola models, and the model values of key photosynthetic parameters were very close to the measured data. There were significant differences in the light responses, biochemical parameters and the parameters of rapid light curves among the oval, serrated broad-oval leaves and lanceolate leaves, but the heteromorphic leaves did not significantly differ in carbon assimilationefficiency. The maximum net photosynthetic rate (Pnmax) of the heteromorphic leaves under saturated intercellular CO2 concentration was higher than under saturated irradiance, indicating that photosynthetic efficiency was limited to the great extent by CO2 supply and regeneration rate of ribulose biphosphate (RuBP). Initial quantum yield (α), initial carboxylation efficiency (CE), Pnmax, photosynthetic capacity (Amax), maximum carboxylation rate (Vcmax) were greater in the oval and serrated broad-oval leaves than in the lanceolate leaves; the serrated broad-oval leaves had the highest light saturation point (LSP), photosynthetic electron transportation rate (ETRmax) and rate of photorespiration (Rp), whereas the lanceolate leaves had the lowest light compensation point (LCP), LSP, α and CE. All the results above indicate that the serrated broad-oval leaves having greater resistance to strong light and higher Rp may be an important mechanism for dissipating excessive light energy and protecting the photosynthetic apparatus from light damage. In contrast, the oval leaves had higher values in α, CE, triose-phosphate utilization efficiency (TPU), PSII actual photochemical efficiency (ΦPSII), leaf nitrogen allocation strategy and low LCP and therefore could maintain high photosynthetic rate in extremely arid areas. The lanceolate leaves had the lowest values in Pn, ΦPSII, and ETR, which would be difficult to meet the individual growth demand because of the low production of photosynthate, and their number declined with growth and distributed mainly toward the lower tree crowns. |
| Keywords: | adaptation mechanism heteromorphic leaves photosynthesis Populus euphratica response parameter |
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