The effects of flooding on aerenchyma formation in the stem of Arundinella anomala var. depauperata Keng, a riparian plant in Three Gorges reservoir area
三峡库区河岸植物野古草(Arundinella anomala var. depauperata Keng)茎通气组织发生对水淹的响应

Arundinella anomala var. depauperata Keng, a graminoid species, distributes extensively at riversides of Yangtze and its tributaries in Three Gorges reservoir area, it is able to tolerate the river flooding every year and develop good plant community at the riversides. Some researchers have demonstrated that some plant species can form aerenchyma when flooding occurs, thereby ameliorating the gas transport within plant and enhancing the tolerance to flooding. To reveal whether flooding may affect the aerenchyma formation in A. anomala var. depauperata and the responses of A. anomala var. depauperata to different flooding regimes, the aerenchyma formation in the stems of A. anomala var. depauperata subjected to various water submersion depths, submersion durations, and submersion modes were investigated. In the experiment, 3 submersion depths (non-submersion control, belowground submersion, complete submersion with 2m water depth), 5 submersion durations (5, 10, 20, 30, 60days), 2 submersion modes (continuous submersion and intermittent submersion) were included. It was found in the experiment that: (1) A. anomala var. depauperata can form aerenchyma in its stem under the condition of non-flooding and the aerenchyma size increased gradually as plant grew. Flooding accelerated the formation of aerenchyma in A. anomala var. depauperata plants, and advanced the aerenchyma formation in flooded plants. (2) The aerenchyma formation in A. anomala var. depauperata plants did not continuously increase with the time of submersion, when the aerenchyma reached to a certain size, the aerenchyma formation did not increase though the plants were still flooded. (3) Submersion depth had some effects on the aerenchyma formation of A. anomala var. depauperata, in general, belowground submerged plants had larger aerenchyma than completely submerged plants. (4) The effects of submersion modes on the aerenchyma formation of A. anomala var. depauperata were dependent on submersion depth. Under the condition of complete submersion, continuously flooded plants had larger aerenchyma than intermittently flooded plants. However, as to belowground submersion, except at the initial period of flooding, continuously flooded plants did not show any difference in aerenchyma size as compared to intermittently flooded plants.