| Broomcorn millet is an important industrial crop and grain crop in arid and semi-arid area. The moisture is a vital factor which restricts the yield and quality of broomcorn millet,the rehydration after water stress at different times or different levels has different effects on crop growth and yield. Therefore, to explore the influence of the rehydration on growth of broomcorn millet after water stress is of great significance for revealing the response mechanism of rehydration of broomcorn millet after water stress under different conditions,and improving the use efficiency of water and the resisting drought and saving water technique of broomcorn millet.Using Yumi 2 as the material, a pot experiment was conducted: take whole growth period adequate water supply as CK. In jointing and heading stage after moderate and severe water stress after re-watering on broomcorn millet root growth, photosynthetic characteristics,antioxidant protective enzyme activity, leaf and stem sheath transport rate and the influence of production, the study reached the following main results.(1) Water stress inhibited the growth of root cap of broomcorn millet, reduced root-shoot ratio, and the root-shoot ratio decreased with the increasing of stress degree. The compensation effect of root growth and physiological reaction of broomcorn millet after rehydration is relatively obvious. The absorption effect of rehydration after severe water stress during the jointing stage of broomcorn millet was better than that of moderate water stress,but the adverse impacts of the root water absorption increased according with the intensification water stress during three leaf stage. At the same time, the ways of water absorption of root varied with the levels of water stress, the water absorption of roots with rehydration after severe water stress mainly depended on the increase of new roots, the excitation of deactivation roots occupied a second role; oppositely, the water absorption of root with rehydration after moderate water stress mainly counted on the excitation of deactivation roots, the increase of new roots was secondary.(2) From the flowering period to maturity, the response of the green leaf area of top 3leaves, chlorophyll content and leaf number on water deficit and rehydration was different.From flowering period to maturity, the green leaf area of moderate and severe water deficitwas respectively 22.5% and 44.6% lower than that of controls; the severe water deficit was more significant. During the jointing stage, the after-effect of leaf number with rehydration of severe water stress was greater than that of moderate water stress, and the leaf number with rehydration of severe water stress was more than that of moderate water stress. During the flowering period, the green leaf area and chlorophyll content was respectively 5.12% and12.5% higher than controls. The increase of chlorophyll content improved the strength of the "source", and was conducive to the accumulation of photosynthetic products. On the contrary,the after-effect of leaf number with rehydration of moderate water stress was greater than that of severe water stress during the heading stage. Meanwhile, the after-effect of leaf number with rehydration after water stress of the jointing stage was greater than that of the heading stage.(3) Leaf photosynthetic rate, stomatal conductance and intercellular CO2 concentration of the broomcorn millet all decreased with the increase of the degree of water stress, the increase of photosynthetic rate after rehydration was the result of the compensation effect of the improved physiological activity of the new organs, but not the result of the recovery of old leaves. Intimidation of old leaves, net photosynthetic rate under stress during or after the complex water showed a decrease trend. Compared with controls, both jointing stage and heading stage after water stress before the growth of leaf net photosynthetic rate is low after water, the heavier stress level net photosynthetic rate is smaller; Dried grow new leaves, and heavy water stress after jointing stage water treatment new leaves net photosynthetic rate is highest, after the water 20 d is 14.5% higher than control, moderate water stress after jointing stage after water new leaves net photosynthetic rate compared with no significant difference;Moderate water stress at 10 d after flowering period after water treatment after water is 10.8%higher than control, but different from jointing stage after water, after water after 10 d net photosynthetic rate began to decrease. 3 leaf stage with severe water stress, therefore, the complex water advantageous physiological activity increases, the new organ for corn millet and photosynthetic rate of root cap function best compensation effect.(4)The effects of water stress and rewatering on the activities of SOD and POD and the content of content of MDA on top clover after flowering were related with stress, rewatering period and stress lasted. After flowering, the activities of SOD and POD on top clover of control were flag leaf > top second leaf > top third leaf and showed first increased then decreased. The appearance time of maximum SOD and POD of moderate and severe water stress were earlier than that of control, but reduced the activities of POD and SOD.Rewatering after moderate and severe water stress at jointing stage improved the activities of SOD and POD on top clover after flowering 6-18 days, rewatering after moderate water stressat heading stage improved the activities of SOD and POD on top clover, rewatering after severe water stress at heading stage improved the activities of SOD and POD, but still lower than that of control, the content of MDA on top clover were top third leaf>top second leaf>flag leaf. Compared with control, under moderate water stress, the content of MDA of rewatering on jointing stage has been low, rewatering on heading stage decreased the content of MDA on top clover after flowering 12-24 days. Under severe water stress, rewatering on jointing stage decreased the content of MDA significantly after flowering and produced contour compensation effect, the content of MDA decreased obviously after rewatering at heading stage.(5)After different degrees of water stress then rewatering, broomcorn millet has different transfer rate and yield. Compared with the photographic, Two treatments of stressed in the whole stages reduced beginning flowering and mature leaves and stem sheath dry weight in different degree.There leaves and stem sheath transfer efficiency reduced 19.7%and 38.7%. After rewatering, every treatments’ leaf dry weight and leaf sheaths has a certain degree of increase.The treatmentof after jointing stage of severe water stress then rewatering effect is best.Its’ leaf sheaths and blades material transport rises high. compared with respectively increased 11.1% and 21.7%. It to the greatest extent promoted the accumulation of production.In one word, different levels of water stress on broomcorn millet will have the different damage and after rewatering will have different recovery.Moderate and severe water stress after heading stage water largely reduces the broomcorn millet root growth, active after flowering of the top 3 leaf green leaves area, net photosynthetic rate, chlorophyll content,antioxidant enzyme activity, reduce the stem sheath material output rate and the transfer rate,to compensate the effect not beautiful, therefore should avoid broomcorn millet long experience in the growth process of water stress.However, severe water stress after jointing stage water broomcorn millet root cap growth activity, the top 3 leaf net photosynthetic rate,seed setting rate were a certain amount of higher contrast, shows that severe water stress after jointing stage water is conducive to the growth and yield of broomcorn millet. |
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