Luo Fang-Li, Chen Yue, Huang Lin, Wang Ao, Zhang Ming-Xiang, Yu Fei-Hai
School of Nature Conservation, Beijing Forestry University, Beijing 100083, China.
School of Nature Conservation, Beijing Forestry University, Beijing 100083, China
Ann Bot. 2014 Jun;113(7):1265-74. doi: 10.1093/aob/mcu057. Epub 2014 Apr 10.
Submergence and de-submergence are common phenomena encountered by riparian plants due to water level fluctuations, but little is known about the role of physiological integration in clonal plants (resource sharing between interconnected ramets) in their adaptation to such events. Using Alternanthera philoxeroides (alligator weed) as an example, this study tested the hypotheses that physiological integration will improve growth and photosynthetic capacity of submerged ramets during submergence and will promote their recovery following de-submergence.
Connected clones of A. philoxeroides, each consisting of two ramet systems and a stolon internode connecting them, were grown under control (both ramet systems untreated), half-submerged (one ramet system submerged and the other not submerged), fully submerged (both ramet systems submerged), half-shaded (one ramet system shaded and the other not shaded) and full-shaded (both ramet systems shaded) conditions for 30 d and then de-submerged/de-shaded for 20 d. The submerged plants were also shaded to very low light intensities, mimicking typical conditions in turbid floodwater.
After 30 d of submergence, connections between submerged and non-submerged ramets significantly increased growth and carbohydrate accumulation of the submerged ramets, but decreased the growth of the non-submerged ramets. After 20 d of de-submergence, connections did not significantly affect the growth of either de-submerged or non-submerged ramets, but de-submerged ramets had high soluble sugar concentrations, suggesting high metabolic activities. The shift from significant effects of integration on both submerged and non-submerged ramets during the submergence period to little effect during the de-submergence period was due to the quick recovery of growth and photosynthesis. The effects of physiological integration were not found to be any stronger under submergence/de-submergence than under shading/de-shading.
The results indicate that it is not just the beneficial effects of physiological integration that are crucial to the survival of riparian clonal plants during periods of submergence, but also the ability to recover growth and photosynthesis rapidly after de-submergence, which thus allows them to spread.
由于水位波动，淹水和退水是河岸植物常见的现象，但对于克隆植物（相互连接的分株之间的资源共享）生理整合在其适应此类事件中的作用知之甚少。本研究以空心莲子草为例，检验了以下假设：生理整合将提高淹水期间被淹分株的生长和光合能力，并促进退水后它们的恢复。
将空心莲子草的相连克隆体（每个克隆体由两个分株系统和连接它们的匍匐茎节间组成）分别置于对照（两个分株系统均不处理）、半淹水（一个分株系统淹水而另一个不淹水）、全淹水（两个分株系统均淹水）、半遮光（一个分株系统遮光而另一个不遮光）和全遮光（两个分株系统均遮光）条件下培养30天，然后进行退水/退荫处理20天。对淹水植物也进行遮光处理，使其光照强度极低，模拟浑浊洪水中的典型条件。
淹水30天后，被淹与未被淹分株之间的连接显著增加了被淹分株的生长和碳水化合物积累，但降低了未被淹分株的生长。退水20天后，连接对退水或未退水的分株生长均无显著影响，但退水后的分株可溶性糖浓度较高，表明其代谢活性较高。从淹水期间整合对被淹和未被淹分株均有显著影响，到退水期间影响较小，这一转变是由于生长和光合作用的快速恢复。未发现生理整合在淹水/退水条件下的影响比遮光/退荫条件下更强。
结果表明，对于河岸克隆植物在淹水期间的存活而言，不仅生理整合的有益作用至关重要，退水后迅速恢复生长和光合作用的能力也很关键，这使得它们能够扩散。
