School of Plant Biology , The University of Western Australia , Crawley 6009, WA , Australia.
AoB Plants. 2011;2011:plr030. doi: 10.1093/aobpla/plr030. Epub 2011 Nov 30.
Wetland plants inhabit flood-prone areas and therefore can experience episodes of complete submergence. Submergence impedes exchange of O(2) and CO(2) between leaves and the environment, and light availability is also reduced. The present review examines limitations to underwater net photosynthesis (P(N)) by terrestrial (i.e. usually emergent) wetland plants, as compared with submerged aquatic plants, with focus on leaf traits for enhanced CO(2) acquisition.
Floodwaters are variable in dissolved O(2), CO(2), light and temperature, and these parameters influence underwater P(N) and the growth and survival of submerged plants. Aquatic species possess morphological and anatomical leaf traits that reduce diffusion limitations to CO(2) uptake and thus aid P(N) under water. Many aquatic plants also have carbon-concentrating mechanisms to increase CO(2) at Rubisco. Terrestrial wetland plants generally lack the numerous beneficial leaf traits possessed by aquatic plants, so submergence markedly reduces P(N). Some terrestrial species, however, produce new leaves with a thinner cuticle and higher specific leaf area, whereas others have leaves with hydrophobic surfaces so that gas films are retained when submerged; both improve CO(2) entry.
Submergence inhibits P(N) by terrestrial wetland plants, but less so in species that produce new leaves under water or in those with leaf gas films. Leaves with a thinner cuticle, or those with gas films, have improved gas diffusion with floodwaters, so that underwater P(N) is enhanced. Underwater P(N) provides sugars and O(2) to submerged plants. Floodwaters often contain dissolved CO(2) above levels in equilibrium with air, enabling at least some P(N) by terrestrial species when submerged, although rates remain well below those in air.
湿地植物栖息在洪水泛滥的地区，因此会经历完全淹没的时期。淹没会阻碍叶片与环境之间的 O(2)和 CO(2)交换，并且光可用性也会降低。本综述检查了与水生植物相比，陆生（即通常是挺水的）湿地植物在水下净光合作用 (P(N))方面的限制，重点是增强 CO(2)获取的叶片特性。
洪水在溶解氧、CO(2)、光和温度方面是可变的，这些参数影响水下 P(N)以及水生植物的生长和存活。水生物种具有形态和解剖学叶片特性，可以减少 CO(2)吸收的扩散限制，从而有助于水下 P(N)。许多水生植物还具有碳浓缩机制，以增加 Rubisco 处的 CO(2)。陆生湿地植物通常缺乏水生植物所具有的许多有益的叶片特性，因此淹没会显著降低 P(N)。然而，一些陆生物种会产生新的叶片，具有更薄的角质层和更高的比叶面积，而其他物种的叶片具有疏水性表面，因此在淹没时会保留气膜；两者都能改善 CO(2)的进入。
淹没会抑制陆生湿地植物的 P(N)，但在水下产生新叶的物种或具有叶片气膜的物种中，抑制作用较小。具有更薄角质层或具有气膜的叶片在洪水中具有更好的气体扩散性，从而增强了水下 P(N)。水下 P(N)为水生植物提供糖和 O(2)。洪水通常含有与空气平衡时的溶解 CO(2)水平以上的溶解 CO(2)，使陆生物种在淹没时至少能够进行一些 P(N)，尽管速率仍远低于空气中的速率。
