Response Mechanisms Of Typical Emerged Plants To Salt And Water Environment In Wetlands Of The Yellow River Delta

The Yellow River Delta new-born wetlands is one of the biodiversity richest areas in the world, and is the most integrated, broadest, youngest wetland ecological system in warm temperate zone of our country. In recent years, it is faced with the threat of high strength of human activity with the development of economy, hydro-ecological processes and water-environment effect become the core problem for it. In this paper, based on the methods of combining the field survey and indoor simulation, the response mechanisms of emerged plant's morphostructure, physiological, biochemical, and breeding characteristics under different salt and water environment in Wetlands of the Yellow River Delta was studied. These study would provide a scientific basis on exploration of coupling mechanism of emerging plant's biological production and hydrological processes, and provide valuable reference foundation for the project of hydro-ecological processes, water-environmental effects and integrated control of ecological security for wetlands in Huang-Huai-Hai region of our country. The main conclusions were obtained as follows:1. The results of seed germination of the four dominant species(Suaeda salsa, Apocynum venetum, Phragmites australis and Typha orientalis)of the newly created wetland indicated that salinity significantly affected the germination percentage and germination rate of seeds of the four species. All species have a trend of decreased germination percentage and rate of germination with the increase of salinity levels, but influence degree of salinity on the germination percentage of each specie was different, which confirmed that salinity is one of the pivotal factors on seed gemination of plants. And the results of seed germination of the four dominant species in the newly created wetland are accorded with the results of field investigate of community distribution along the gradients of environmental salinity. Further revealed salinity is one of the most pivotal factors limited the distribution of the plant vegetation in the newly created wetland of Yellow River Delta.2. As the dominant emerged plant in Yellow River Delta, P.australis showed vary physiological indexes under the condition of different water depth and salinity, and in the tolerance range, P.australis through increased intracellular soluble sugar content, POD and CAT activities to quickly adapt the salt and drought environment.3. There were obvious differences in the morphological structure of the leaves and root of P.australis among different geomorphological locations in Yellow River Delta. Compared to the P. australis grown in wet areas, the P. australis grown in drought areas had thicker leaves, smaller bubbly cells and more developed vascular tissue, the phenomenon of stomatal subsidence alse be founded. These characteristics were helpful to decrease water transpiration, and promote water transportation and migration of nutrient elements under the condition of decrease of transpiration; The P. australis grown in drought areas had less quantity of cortexlayers of root than which growth in wet areas. These characteristics make it possible to shorten the transverse transportation distance of water. Morever, the aerenchyma of root was more developed in the wet ares than that in the drought areas, which makes it could adapt the hypoxia caused by water stress. These structure characteristics reflected the adaptive mechanisms of P. australis to drought and salt stress, also reflects the reeds have strong ability to adapt to the environment.