| On the basis of lead and rhythmic water change in different growth period, regarding the different variations of soil water supply as three phase factors, this study used quadratic regression rotary design of three factors to studies and illustrates the rules of lead and rhythmic moisture stress on Amorpha fruticosa and Sophora japonica seedlings growth, photosynthetic and water physiology, and tries to seek the optimal water supply combination for different indexex, in order to provide technical and theoretical foundations for vegetation restoration and reconstruction of arid and semi-arid lead-zinc mining area. The main research conclusions are as follows:1. When the relative soil moisture content is 100%, chlorophyll a, chlorophyll b and chlorophyll(a+b) of Amorpha fruticosa seedlings under the stress of lead are significantly lower than control CK(P < 0.05); chlorophyll a content of Sophora japonica is lower than CK, and chlorophyll b and chlorophyll(a+b) are significantly higher than CK. Under the dual stress, chlorophyll a and chlorophyll(a+b) of Sophora japonica and Amorpha fruticosa increase firstly then decrease as water stress increase, and reach the maximum when relative soil water content is 70%. Water stress causes the decline of chlorophyll a/b ratio. Soil relative moisture content of the early growth and middle growth stage had the significant influence on chlorophyll content of Amorpha fruticosa, Sophora japonica showed the order: the middle growth stage > the early growth stage > the terminal growth stage.2. When the relative soil moisture content is 100%, a certain concentration of lead promote the net photosynthetic rate of Amorpha fruticosa, but has an inhibition on Sophora japonica. Under the dual stress, net photosynthetic rate of Amorpha fruticosa showed a down trend with water stress increasing, and reached the minimum when the relative soil water content was 52.16%. Net photosynthetic rate of Sophora japonica showed a reduction-increase- decreases trend, and drop to the minimum when the relative soil water content was 40%. Under lead stress, WUE of Amorpha fruticosa seedling increased firstly then decreased and increased last with the intensification of water stress. It reached the maximum when the SRW is 40%; WUE of Sophora japonica seedling showed the same trend. It drop to the minimum when SRW is 52.16%.Soil relative moisture content of tetminal growth had the greatest influence on Pn of Amorpha fruticosa and Sophora japonica, followed by the early growth stage, and the middle growth stage the least.3. Lead stress significantly reduced the water saturation deficit of Sophora japonica and Amorpha fruticosa when the water is plentiful, while the leaf water potential elevated slightly. Under lead stress, leaf relative water content of Sophora japonica and Amorpha fruticosa declined with the decrease of soil moisture, while water saturation deficit trend is opposite. Leaf water potential of Sophora japonica and Amorpha fruticosa are showing a continuous decrease trend with the intensification of water stress.Under lead stress, water supply at the terminal growth stage had a significantly effect on water saturation deficit and leaf water potential of Sophora japonica and Amorpha fruticosa, while the water supply at middle and late growth stage had no significant influence on water physiology. Soil relative moisture content of the middle growth had the greatest influence on PLC of Amorpha fruticosa and Sophora japonica, followed by the early growth stage, and the terminal growth stage the least.4. Lead stress inhibits the ground diameter growth of Amorpha fruticosa when soil moisture is enough, but promoted the height growth; and a certain concentration of lead inhibited height growth and diameter growth of Sophora japonica. Under the dual stress, with the increase of water stress, the height increment and ground diameter growth of Amorpha fruticosa and Sophora japonica all showed a trend of decrease, reached the least when SRW was 40%.Under the lead stress, soil relative moisture content of the early growth had the greatest influence on height increment of Amorpha fruticosa, followed by the middle growth stage, and the terminal growth stage the least; and ground diameter growth is: the middle growth stage > the early growth stage > the terminal growth stage. For Sophora japonica, soil relative moisture content of the early growth had the greatest influence on height increment and ground diameter growth, followed by the middle growth stage, and the terminal growth stage the least. Soil relative moisture content of the middle growth had the greatest influence on biomass of Amorpha fruticosa, followed by the early growth stage, and the terminal growth stage the least. For Sophora japonica, influence on biomass of three stages soil water supply showed the order: the early growth stage > the middle growth stage > the terminal growth stage. Effects of water supply at different growth stage are that biomass of Amorpha fruticosa and Sophora japonica decreases gradually as water stress increased.5. Using comprehensive principal component analysis to analyse the influence of different moisture combination processing on Amorpha fruticosa and Sophora japonica.The results show that PLC, biomass and plant height growth play main roles in values for Amorpha fruticosa; biomass and plant height, ground diameter, PLC value play main roles in values of Sophora japonica. Effects of water supply at different growth stage are that comprehensive principal component values of Amorpha fruticosa and Sophora japonica gradually decreases as water stress increased. With frequency analysis respectively, the results showed that when the water combination is 94.35%~100.00% in early stage, 91.36%~100.00% in middle stage and 82.28%~99.62% in late stage, the comprehensive growth value of Amorpha fruticosa is 95 percent higher than 80% of maximum; For Sophora japonica, the water combination is 93.31%~100.00% in early stage, 89.92%~100.00% in middle stage and 87.48%~97.93% in late stage. |
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