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.
The widespread and frequent drought events have caused serious crop yield losses. A better understanding of the yield response to drought plays an important role in accurately assessing the impact of drought and managing yield production. Based on the arranged experimental platform of drought-rewetting (CK for natural precipitation treatment; RD for water control from 30 June to 10 August 2020, followed by rewetting to CK) in the Jinzhou Agricultural Weather Experiment Station, net photosynthetic rate (Pn), transpiration rate (Tr) daily stem flow (DSF) and maize yield component factors are measured. The results show that Pn decrease by 5.0% and Tr increase by 12.4% at the beginning of water control of RD treatment at the jointing stage compared with CK treatment, but the trends are not significant. At the grain filling stage, when soil water content (SWC) are less than 40.0%, Pn, Tr and DSF under RD treatment significantly reduce to 23.6%, 6.9% and 32.5% of those under CK treatment, respectively. Moreover, most of the photosynthetic products of leaves were transported to the ear during the grain filling stage, and water consumption is greater than that of the jointing stage, leading to the obvious inhibitory effect of water stress on Pn, Tr and DSF. At the milk-ripe stage, RD treatment entered the rewetting stage, Pn, Tr and DSF increase and recovere to 61.5%, 75.0% and 46.6% of those under CK treatment, respectively, indicating that decreased Pn, Tr and DSF during the water control period could not be completely recovered during this period. Correlation analysis showe that Pn and Tr significantly reduce during the period of water control by reducing leaf water ratio (LWR) and stem water ratio (SWR). The correlation of LWR with Pn and Tr are 0.57 and 0.84, and the correlation of SWR with Pn and Tr are 0.59 and 0.67. Continuous water control from jointing stage to filling stage may lead to the decrease of photosynthetic organ activity, and rewetting fails to restore it, eventually leading to crop yield reduction. Compared with CK treatment, spike length, spike diameter and 100 grain weight under RD treatment decrease significantly, resulting in a yield reduction rate of 54.0%.
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 (Pn) 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 Pn of spring maize leaves under WS-35 treatment was the highest, and Pn 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 Pn 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 (Tr) increased with temperature increasing. When the water supply was insufficient, compared with CK-40 treatment, the Tr and stomatal limitation (Ls) of spring maize leaf decreased significantly (P<0.05), while intercellular CO2 concentration (Ci) increased significantly (P<0.05) under WS-40 treatment. With the increase of PAR, Tr 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 one of the major agro-meteorological disasters to restrict the improvement of grain production and quality in China. The soil moisture and mineral elements affect alternately to the growth and development of winter wheat as well as the yield and quality. The response of leaves mineral elements accumulation, yield and grain quality of winter wheat to different grades drought stress was explored at the moisture critical period, which has a certain realistic significance to scientific fertilization and drought disaster prevention. At the moisture critical period (jointing to flowerings stage), the winter wheat ‘Qimai 2’ was used as material to set the water control experiments with five gradients (T1 treatment, soil moisture at 20 cm depth was suitable (60%-80%) in the whole period, and T2, T3 and T4 treatments were supplied once with water at 80%, 50% and 25% of 75.0 mm base recharge, respectively, while T5 treatment wasn’t supplied water)， the influences of drought stress on the accumulation of nitrogen, phosphorus and potassium mineral elements, photosynthetic pigments and photosynthetic parameters, yield and grain quality of winter wheat were simulated and analyzed. The results show that the total nitrogen, total phosphorus, photosynthetic pigment content and the maximum net photosynthetic rate (Pnmax), apparent quantum efficiency (AQE) and light saturation point (LSP) of winter wheat leaves were all the highest under T1 treatment during the water control to rewatering. Due to drought stress, the above-mentioned indicators reduced significantly under T2, T3, T4 and T5 treatments, and the heavier the drought stress, the greater the reduction was. Compared with T1 treatment, the total nitrogen, total phosphorus content, chlorophyll a, chlorophyll a+b, carotenoid content, Pnmax, AQE and LSP of leaves reduced by 1.68%, 0.15%, 0.90 mg·g-1, 1.05 mg·g-1, 0.21 mg·g-1, 64.6%, 65.8% and 31.2% under T5 treatment, respectively. However, the total potassium content and light compensation point (LCP) of leaves increased with the aggravation of drought stress, and those under T5 treatment were 1.20% and 84.0% higher than under T1 treatment, respectively. In addition, the drought stress decreased significantly spike grains number, forming spike rate and thousand grains weight. Compared with T1 treatment, the theoretical yield and grain protein content decreased by 56.6% and 30.1%, respectively, while the grain starch content increased by 11.6% under T5 treatment.
As the fourth major staple crop after rice, wheat and corn, potato is of great significance for ensuring the national food security. In order to explore the response characteristics of potato (Solanum tuberosum L.) yield, leaf photosynthetic physiology, dry matter accumulation characteristics to water stress in the semi-arid region of the Loess Plateau, the soil water stress experiment was conducted in 2021 by using the main potato variety “Xindaping” as the test material. The soil water was controlled during the critical period of tuber enlargement (August). Field water capacity was set at 40%±5% (moderate water stress, T1 treatment) and 55%±5% (mild water stress, T2 treatment), and 75%±5% (full water treatment, T3) was used as the control for analysis. The results show that under water stress, the maximum tuber weight per plant, tuber weight per plant and yield all decreased, the number of tubers decreased, the weight and the number of pellet potato increased significantly (P<0.05), and compared with T3 the yield of potato under T1 and T2 treatments decreased by 30% and 13%, respectively. The net photosynthetic rate (Pn), stomatal conductance (Gs) and intercellular CO2 concentration (Ci) of potato leaves decreased significantly, among them the Gs decreased by 59%, and the water use efficiency (WUE) of T1 treatment was 31% higher than that of T3. In the weak light area, the effect of moderate and mild water stress on Pn is not obvious (P>0.05), when the light intensity was higher than 300 μmol·m-2·s-1, the differences between treatments increased, and Pn under T1 and T2 treatments decreased by 42% and 32% on average compared with T3. Under the influence of water stress, the maximum net photosynthetic rate (Pnmax), light compensation point (LCP) and dark respiration rate (Rd) decreased significantly (P<0.05), and light saturation point (LSP) under mild water stress was the highest (893.32 μmol·m-2·s-1). The range of available photosynthetically active radiation (PAR) of leaves decreased under moderate water stress, and the ability to use strong light decreased. The dry matter weight of roots, stems, leaves and petioles decreased under water stress, and under moderate water stress, the petiole decreased the most (63%), followed by leaves (57%) and roots (50%). This study can provide theoretical basis for potato drought damage assessment and soil water efficient utilization in semi-arid area of Loess Plateau.
