Fernàndez-Martínez J, Fleck I
Departament de Biologia Vegetal, Unitat de Fisiologia Vegetal, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain.
Plant Biol (Stuttg). 2016 Jul;18(4):638-48. doi: 10.1111/plb.12439. Epub 2016 Feb 17.
Information on the photosynthetic process and its limitations is essential in order to predict both the capacity of species to adapt to conditions associated with climate change and the likely changes in plant communities. Considering that high-mountain species are especially sensitive, three species representative of subalpine forests of the Central Catalan Pyrenees: mountain pine (Pinus uncinata Mill.), birch (Betula pendula Roth) and rhododendron (Rhododendron ferrugineum L.) were studied under conditions associated with climate change, such as low precipitation, elevated atmospheric [CO2 ] and high solar irradiation incident at Earth's surface, in order to detect any photosynthetic limitations. Short-term high [CO2 ] increased photosynthesis rates (A) and water use efficiency (WUE), especially in birch and mountain pine, whereas stomatal conductance (gs ) was not altered in either species. Birch showed photosynthesis limitation through stomatal closure related to low rainfall, which induced photoinhibition and early foliar senescence. Rhododendron was especially affected by high irradiance, showing early photosynthetic saturation in low light, highest chlorophyll content, lowest gas exchange rates and least photoprotection. Mountain pine had the highest A, photosynthetic capacity (Amax ) and light-saturated rates of net CO2 assimilation (Asat ), which were maintained under reduced precipitation. Furthermore, maximum quantum yield (Fv /Fm ), thermal energy dissipation, PRI and SIPI radiometric index, and ascorbate content indicated improved photoprotection with respect to the other two species. However, maximum velocity of carboxylation of RuBisco (Vcmax ) indicated that N availability would be the main photosynthetic limitation in this species.
为了预测物种适应气候变化相关条件的能力以及植物群落可能发生的变化，了解光合作用过程及其限制因素至关重要。鉴于高山物种特别敏感，对加泰罗尼亚中部比利牛斯山脉亚高山森林的三种代表性物种进行了研究：山松（Pinus uncinata Mill.）、桦树（Betula pendula Roth）和杜鹃花（Rhododendron ferrugineum L.），研究条件为与气候变化相关的情况，如降水少、大气[CO₂]浓度升高以及地球表面入射的太阳辐射高，以检测任何光合作用限制。短期高[CO₂]浓度提高了光合速率（A）和水分利用效率（WUE），尤其是在桦树和山松中，而两种物种的气孔导度（gs）均未改变。桦树因降雨少导致气孔关闭而出现光合作用限制，这引发了光抑制和叶片过早衰老。杜鹃花尤其受到高辐照度的影响，在低光照下表现出早期光合饱和、叶绿素含量最高、气体交换率最低且光保护作用最小。山松具有最高的A、光合能力（Amax）和净CO₂同化的光饱和速率（Asat），在降水量减少的情况下仍能维持。此外，最大量子产量（Fv/Fm）、热能耗散、PRI和SIPI辐射指数以及抗坏血酸含量表明，与其他两个物种相比，其光保护作用有所改善。然而，RuBisco羧化的最大速度（Vcmax）表明，氮的有效性将是该物种光合作用的主要限制因素。
