| Drought is the mostly important limiting factor of agricultural yielding. Improving water use efficiency of crops is the key of saving-water agriculture. In the region of mudflats along the coast, irrigating salt-tolerant plant with seawater can not only save limited fresh water resources, but also may improve water use efficiency of salt-tolerant plant in the condition of lower drought and seawater irrigation of low concentrations. And it provides a new method to sustainable development of agriculture in coastal regions. Consequently, the further study, especially the research of salt resistance and its water use efficiency is very important for the further use of Jerusalem artichoke, and there's also significant meaning to exploit and make use of the plants in mudflats.There were three parts in this research: seawater irrigation experiments; seawater irrigation and drought stress experiments; exogenous calcium ameliorating seadrought stress experiments.The main results were as follows:Seawater irrigation experiments:The growth and development, photosynthesis, water consumption and related physiological and biochemical indices of Jerusalem artichoke seedlings irrigated with seawater of different concentrations under soil culture of pot experiment were studied to find out the effect of seawater irrigation on Jerusalem artichoke seedlings from different angles. And the suitable seawater concentration that was fit for the growth and could promote its water use efficiency was selected. The results were showed as below:(1) There were significant influences of seawater irrigation on the height, biomass, net photosynthesis, conductance, leaf water use efficiency, etc of Jerusalem artichoke seedlings. And the roots would grow towards the deeper soil with seawater irrigation.(2) Influences were existed in physiological indices of leaves under seawater irrigation, and osmotic potential of soil didn't hurt NY2 under the irrigation of 5% and 10% seawater. But high osmotic stress had decreased water content in cell when irrigated with seawater of 30% and 40%, and it also affected photosynthesis and water use efficiency, therefore inhibited its growth. In short, the most favorable concentration was 10%, and in this condition, water, photosynthesis and biomass etc were all in accordance with the requirements of physiology and production.Seawater irrigation and drought stress experiments:Jerusalem artichoke in pot was grown to simulate drought stress and seawater irrigation in fields on the basis of seawater irrigation experiment, in order to study the influences on growth and development, photosynthesis, water consumption characteristics and water use efficiency of Jerusalem artichoke with irrigation of seawater under drought stress. The results were showed as below:(1) The plants grew well irrigated with seawater of 10% and soil water being between 75% and 85%, but its leave water use efficiency and biomass water use efficiency were not high enough. While the plants irrigated with seawater of 10% and being suitable drought stress had higher water use efficiency.(2) The plants grew well with full fresh water irrigation, but they showed the inelasticity to seawater irrigation of 20% and drought stress.(3) The treatment of 10% seawater irrigation and suitable drought showed superiority in growth and development and physiological characteristics, especially it had higher water use efficiency. Therefore, Jerusalem Artichoke can be grown in semi-drought regions which irrigated with seawater.Exogenous calcium ameliorating seadrought stress experiments:(1) Exogenous calcium could ameliorate seadrought stress on Jerusalem artichoke seedlings. The treatment of exogenous calcium had higher biomass compared with one which irrigated with the same concentration of seawater, and the resistance to seadrought stress were also increased.(2) It could also improve containing water ability of leaves by exogenous calcium, and it also promote leave water use efficiency.
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