Institut für Phytosphäre, ICG-3, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
Ann Bot. 2009 Dec;104(7):1435-44. doi: 10.1093/aob/mcp257. Epub 2009 Oct 23.
Concomitant increases in O(2) and irradiance upon de-submergence can cause photoinhibition and photo-oxidative damage to the photosynthetic apparatus of plants. As energy and carbohydrate supply from photosynthesis is needed for growth, it was hypothesized that post-submergence growth recovery may require efficient photosynthetic acclimation to increased O(2) and irradiance to minimize photo-oxidative damage. The hypothesis was tested in two flood-tolerant species: a C(3) herb, Alternanthera philoxeroides; and a C(4) grass, Hemarthria altissima. The impact of low O(2) and low light, typical conditions in turbid floodwater, on post-submergence recovery was assessed by different flooding treatments combined with shading.
Experiments were conducted during 30 d of flooding (waterlogging or submergence) with or without shading and subsequent recovery of 20 d under growth conditions. Changes in dry mass, number of branches/tillers, and length of the longest internodes and main stems were recorded to characterize growth responses. Photosynthetic parameters (photosystem II efficiency and non-photochemical quenching) were determined in mature leaves based on chlorophyll a fluorescence measurements.
In both species growth and photosynthesis recovered after the end of the submergence treatment, with recovery of photosynthesis (starting shortly after de-submergence) preceding recovery of growth (pronounced on days 40-50). The effective quantum yield of photosystem II and non-photochemical quenching were diminished during submergence but rapidly increased upon de-submergence. Similar changes were found in all shaded plants, with or without flooding. Submerged plants did not suffer from photoinhibition throughout the recovery period although their growth recovery was retarded.
After sudden de-submergence the C(3) plant A. philoxeroides and the C(4) plant H. altissima were both able to maintain the functionality of the photosynthetic apparatus through rapid acclimation to changing O(2) and light conditions. The ability for photosynthetic acclimation may be essential for adaptation to wetland habitats in which water levels fluctuate.
重新浮出水面时 O(2) 和光照的同时增加可能会导致植物光合作用器官的光抑制和光氧化损伤。由于光合作用产生的能量和碳水化合物供应是植物生长所必需的，因此推测，后淹没生长恢复可能需要光合作用的有效适应，以增加 O(2) 和光照，最大限度地减少光氧化损伤。该假设在两种耐淹没的物种中进行了测试：一种 C(3) 草本植物，Alternanthera philoxeroides；和一种 C(4) 草，Hemarthria altissima。通过不同的淹没处理与遮光相结合，评估了低 O(2) 和低光照（混浊洪水的典型条件）对淹没后恢复的影响。
在 30 天的淹没（水浸或淹没）期间进行实验，有或没有遮光，并在生长条件下随后恢复 20 天。记录干质量、分枝/分蘖数以及最长节间和主茎的长度变化，以表征生长反应。根据叶绿素 a 荧光测量，在成熟叶片中测定光合作用参数（光系统 II 效率和非光化学猝灭）。
在两种物种中，生长和光合作用在淹没处理结束后都得到了恢复，光合作用的恢复（在重新浮出水面后不久开始）早于生长的恢复（在第 40-50 天明显）。光系统 II 的有效量子产率和非光化学猝灭在淹没期间降低，但在重新浮出水面后迅速增加。所有遮光植物，无论是否淹没，都有类似的变化。尽管淹没植物的生长恢复受到阻碍，但在整个恢复期间它们并未遭受光抑制。
在突然重新浮出水面后，C(3) 植物 A. philoxeroides 和 C(4) 植物 H. altissima 都能够通过快速适应不断变化的 O(2) 和光照条件来维持光合作用器官的功能。光合作用的适应能力对于适应水位波动的湿地生境可能至关重要。
