| Along with the economical development in our country, the shortage of water resource is more and more serious. Drought and water shortage have become one of the most essential factors to stress the agricultural development in the northern arid area in China. Water saving irrigation is the great subject in agricultural production. Water stress is the most extensive adverse circumstance for crops to grow in the field. And proper water stress is beneficial for water saving irrigation and crops'growing. To understand the crops'response to such adverse circumstance is the prime to realize the rational control of crops and water saving irrigation. In order to reduce the waste of water resource during the irrigation, utilizing alternate partial root-zoon irrigation (APRI), which is the manmade irrigation method with partial root water stress, is the new breakthrough of regular irrigation methods.On the basis of previous research, and through the comparison and analysis with two years greenhouse capsicum's experiment of APRI with different irrigation low limits (40%θF,60%θF,80%θF), this research studied the influence of different water stress to the growth and physiological characteristics, and identified the optimal irrigation low limit and the sensitiveness of different indexes of moisture deficit diagnosis for greenhouse capsicum under APRI. This research offered theoretical support for the optimal water using method and the sieving of the index of moisture deficit diagnosis of"high yield, high quality, high efficiency"agriculture. The main research conclusions are the following.1) Through many information of ground temperature, it is analyzed that the ground temperature amplitude among each moment in different depth and the ground temperature variation gradient at the same time can be fitted to exponential function with ground depth; sallow layer ground temperature and air temperature are linear correlation in different treatment; the mean ground temperature of wet side and dry side in APRI is all higher than that of general irrigation, and the ground temperature of dry side is always higher than that of the wet side and general irrigation. So that we can make sure the temperature of one side root might not fall suddenly during the irrigation, and in that way the ground temperature around the root zone can be increased to some extend, which can offer a favorable temperature environment for the growth of crops'root system.2) To different treatments including general irrigation (T) and 80%θF (T3),60%θF(T2),40%θF(T1) of alternate partial root-zoon irrigation,the intensity of evaporation among the crops, the accumulation of capsicum's biomass and root hydraulic conductivity are all proportional to the amount of irrigation; the tendency is T>T3>T2>T1; the intensity of water consumption during the growth stage in different treatments is fruiting stage>flowering-fruit stage>seedling stage, and the water consumption during the growth stage in general irrigation treatment is the highest. APRI can reduce the ineffective evaporation among the crops effectively. In T and T3 treatments, the capsicum had growth redundancy. In T2 treatment, the root-shoot ratio was obviously optimized, and the production, water use efficiency (WUE) and quality were all under better lever.3) The capsicum production and WUE of yield of APRI have obviously quadratic curve correlation with irrigation low limit. In order to reach a high production, the irrigation low limit should be controlled around 65%θF, while in order to save water and reach high efficiency, the irrigation low limit should be controlled around 63%θF.4) Making comprehensive evaluation through input, output and efficiency of each lower limit of irrigation, I found that the economical efficiency of T2 treatment under irrigation low limit of 60%θF was the best, T3 treatment under irrigation low limit of 80%θF was worse, and T1 treatment under irrigation low limit of 40%θF was the worst, that is the economical efficiency was T2>T3>T>T1. Analyzing with quality and WUE, we found that capsicum production in APRI under irrigation low limit of 60%θF not only had higher production, but also had higher WUE, and better nutrition quality and commodity value than other treatments, which can be the optimal irrigation model of greenhouse capsicum for extension.5) Through path analysis as a mathematic method, three index----the soil moisture, capsicum physiological ecology and weather, are analyzed with capsicum production, WUE of yield and quality (the content of Vc). It is found that considering the optimal production as the goal, the index of moisture deficit diagnosis is most sensitive with leaf evaporation, less sensitive with soil moisture and stomatal conductance; considering optimal WUE of yield as the goal, also the index of moisture deficit diagnosis is most sensitive with leaf evaporation, less sensitive with leaf temperature and the vapor pressure deficit(VPD); while considering the content of Vc as the goal, the index of moisture deficit diagnosis is most sensitive with soil moisture, less sensitive with fruit water content and effective radiation of photosynthesis.
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