Míguez Fátima, Fernández-Marín Beatriz, Hernández Antonio, Becerril José Maria, García-Plazaola José Ignacio
Department of Plant Biology and Ecology, University of Basque country (UPV/EHU) Apdo 644, 48080 Bilbao, Spain.
Funct Plant Biol. 2015 Feb;42(2):175-185. doi: 10.1071/FP14083.
European mistletoe (Viscum album L.) is a hemiparasitic plant with perennial leaves and photosynthetic stems easily discernible according to their age. These properties make V. album the perfect species to (i) compare the mechanisms of seasonal acclimation of photosynthetic stems with those of leaves, and (ii) evaluate the influence of ageing in the efficiency of photosynthetic tissues. To achieve these general objectives, photosynthetic pigments, maximal photochemical efficiency of PSII (Fv/Fm), recovery kinetics and key thylakoidal proteins were analysed during winter and spring in leaves and at different age stems. During winter, some woody species are able to maintain photosynthetic activity, but at lower rates than during spring. In the case of V. album, photosynthetic relevance of green stems appears equal to leaves in terms of total area. Besides, mistletoe stems are able to maintain higher Fv/Fm and lower level of antioxidants than leaves, especially during winter season. The recovery from winter photoinhibition is also faster in stems than in leaves. Thylakoidal protein composition (mainly high levels of D1) also supports the idea of stems as main photosynthetic organs in V. album during winter. Further, in winter, the level of photoinhibition of V. album stems decreased concomitantly with ageing. This work highlights the importance of stem photosynthesis in plant carbon balance and demonstrates that ageing does not necessarily imply a loss of vitality in stems.
欧洲槲寄生（白果槲寄生Viscum album L.）是一种半寄生植物，其叶片多年生，光合茎根据年龄易于区分。这些特性使白果槲寄生成为理想的物种，可用于（i）比较光合茎与叶片的季节性适应机制，以及（ii）评估衰老对光合组织效率的影响。为实现这些总体目标，在冬季和春季对叶片以及不同年龄的茎进行了光合色素、PSII最大光化学效率（Fv/Fm）、恢复动力学和关键类囊体蛋白的分析。在冬季，一些木本植物能够维持光合活性，但速率低于春季。就白果槲寄生而言，绿色茎的光合相关性在总面积方面似乎与叶片相当。此外，槲寄生茎能够维持比叶片更高的Fv/Fm和更低水平的抗氧化剂，尤其是在冬季。茎从冬季光抑制中的恢复也比叶片更快。类囊体蛋白组成（主要是高水平的D1）也支持了冬季白果槲寄生茎作为主要光合器官的观点。此外，在冬季，白果槲寄生茎的光抑制水平随着衰老而降低。这项工作突出了茎光合作用在植物碳平衡中的重要性，并表明衰老不一定意味着茎活力的丧失。
