In order to explore the response mechanism of photosynthetic physiological process of spring maize to soil water and temperature changes in semi-arid region of the Loess Plateau under the background of climate change, taking spring maize as the research object, the pot water control experiment was carried out in the Dingxi Arid Meteorology and Ecological Environment Experimental Base of China Meteorological Administration in 2017. Control treatment (CK treatment, soil moisture at 80% of field water capacity) and water treatment (WS treatment, soil moisture at 45%-50% of field water capacity) were set at spring maize seven-leaf stage. Three leaf temperature gradients were set, which were optimum temperature 25 ℃, high temperature 35 ℃ and extreme high temperature 40 ℃ (CK treatment corresponds to CK-25, CK-35 and CK-40; WS treatment corresponds to WS-25, WS-35 and WS-40). The response characteristics of leaf gas exchange parameters and water use efficiency to soil moisture and temperature changes at seven-leaf stage of spring maize were analyzed. The results show that within a certain range of photosynthetically active radiation (PAR), the net photosynthetic rate (P_n) of leaves gradually increased with the increase of PAR. When water supply was insufficient, with the increasing of PAR, stomatal limiting factors of spring maize leaves under WS treatment transferred to non-stomatal limiting factors, and photosynthesis is inhibited obviously. The P_n of spring maize leaves under WS-35 treatment was the highest, and P_n of maize leaves under WS treatment was significantly lower than that under CK treatment in the PAR high value area. The PAR at light saturation point decreased under different temperature gradients. Compared with CK-40 treatment, the P_n of spring maize leaf under WS-40 treatment decreased significantly with the increase of PAR (P<0.05), and photoinhibition was obvious. When the water supply was sufficient, the transpiration rate (T_r) increased with temperature increasing. When the water supply was insufficient, compared with CK-40 treatment, the T_r and stomatal limitation (L_s) of spring maize leaf decreased significantly (P<0.05), while intercellular CO₂ concentration (C_i) increased significantly (P<0.05) under WS-40 treatment. With the increase of PAR, T_r decreased and water use efficiency (WUE) of spring maize treated by WS-40 was higher than that CK treatment. This study can provide reference for the physiological characteristics of spring maize in semi-arid region of the Loess Plateau under the background of climate change.

Drought is a major meteorological disaster with the highest frequency, the longest duration and the widest scope of harm in the world today, which has a huge and extensive impact on agriculture, ecology, social development and national economy all over the world. The drought is an important factor affecting agricultural production which determines the stability of crop production, further relates to the national food security. China is a large agricultural country, and also is a country with frequent drought disaster. Therefore, to improve the monitoring, forecasting and warning level of agricultural drought disaster, it is necessary to deeply understand its formation, influence characteristics, drought intensity, severity and physiological process and mechanism of crop victimization. It is also an important scientific problem to reduce and prevent drought disaster losses and improve national food security production. This paper comprehensively reviews the recent internal and overseas research progress of agricultural drought with different degrees and its impact on crop production, and explores the influence characteristics and mechanism of drought from the aspects of crop morphology, physiology, cellular and molecular levels, etc. The main indicators, indexes, methods and early warning systems in current agricultural drought monitoring are reviewed around food production to cope effectively agriculture drought. According to the new characteristics of agricultural sustainable development and drought, the current situation of drought disaster prevention and mitigation and agricultural drought coping are discussed. A series of drought coping measures both adaptation and mitigation are emphasized. On this basis, combining with the needs of national, regional and industrial development, the paper puts forward the important scientific problems, research countermeasures and the prospect of discipline development which should be emphasized in the future.

As the impact of climate warming on agro-ecosystems intensifies, the arid and semi-arid crops in the northwest, where water resources are extremely scarce, will face major challenges. In this paper, the water control starts from the corn tasseling period to the end of the growth period (T1 treatment) and the natural drought at the whole growth period (T2 treatment) in arid and semi-arid regions, the similarities and differences of the formation of drought disasters to the same crop were revealed in arid and semi-arid regions, in order to provide a theoretical basis for grasping the crop drought inducing-disaster process in different climatic regions. The results showed that different drought stresses affected significantly the plant height, leaf area and chlorophyll content of maize in arid and semi-arid regions. During the whole growth period of drought treatment, the response of maize in arid area to drought stress was more sensitive than that in semi-arid area, while T1 treatment had more significant effects on the growth of maize plant height and leaf area per plant in semi-arid rain-fed area. The leaf area per plant of maize under different drought treatments in semi-arid area showed an increasing trend from the horse chestnut stage to grain filling stage as a whole. Although drought stress reduces the leaf area per plant of maize, in order to ensure the later growth and development of plants, the increase of leaf area make up for the lack of photosynthetic yield due to drought stress. Therefore, in order to ensure the yield of maize in arid and semi-arid regions, semi-arid areas are suitable for planting varieties with strong photosynthetic capacity, arid areas are suitable for planting varieties with suitable plant height and leaf area, and the tasseling period is a sensitive period for maize growth and development to drought in semi-arid regions.

In order to study the effect of warming on field water characteristics of spring wheat，the field experiments that temperature was increased by an infrared radiator were designed at Dingxi experiment station in semi － arid area of the Loess Plateau in central Gansu． The results showed that with the increase of temperature，leaf water potential was lowered． Compared with no warming，warming of 1． 0 ℃ and 2． 0 ℃ reduced daily average leaf water potential by 2． 61% and 4． 45%，respectively． Soil water potential increased with increase of soil depth gradually． With the increase of temperature，soil water potential at different soil depth showed a decreasing trend， the higher temperature was，the greater decline of soil water potential was． There was negative correlation between warming and soil water content． Warming significantly decreased soil water storage of spring wheat，and increased evapotranspiration． Under the conditions of warming 2 ℃，irrigation increased the total storage capacity of soil，especially after jointing stage． Soil water consumption amount increased with the increase of temperature ( 0 － 100 cm) ，while the variation tendency of soil water consumption amount was not obvious ( 100 － 160 cm) ． When temperature was increased by 2 ℃，soil water consumption amount of wet treatment was higher than that of the normal water supply and drought treatment for 0 － 160 cm soil depth．