| Drought is the important limiting factor for maize production.Photosynthesis is key metabolic process of corn production,which provides the main material basis of maize yield.The direct effect of drought on maize is the decline in photosynthesis.Rehydration can increase the photosynthetic rate of leaves and accelerate plant′s growth.To a certain extent,rehydration compensates for the damage caused by drought and maintain high yield on maize.Therefore,in-depth study on the photosynthetic physiological response mechanism of maize under drought and re-watering is of great significance to improve the yield,as well as to develop drought resistant and water saving cultivation techniques is of great significance.In this study,thirteen maize cultivars（shaandan609,zhengdan958,shaandan902 et al.）were subjected to drought and re-watering.The drought tolerance of these 13 maize varieties was estimated by analyzing the drought resistance coefficient and drought resistance index based on yield.Two maize cultivars including drought-tolerant‘shaandan609’and drought-sensitive‘shaandan902’were subjected to drought stress and re-watering in pot experiment.We used chlorophyll fluorescence technology to investigate the photosynthetic response characteristics and photosynthetic gene expression in different drought-tolerant varieties,and it will provide a scientific basis for maize drought-resistant breeding.Give the results as follows:1.The yield,drought resistance coefficient and drought resistance index of 13 maize varieties showed significant difference in irrigation and arid areas.The results showed that shaandan609（SD609）,zhengdan958（ZD958）and xianyu335（XY335）had high drought resistance coefficient and drought resistance index,high yield and good productivity,and good stability and strong drought resistance;the shaandan902（SD902）,shaandan8806（SD8806）,jindan81（JD81）,yuyu22（YY22）,weike702（WK702）,qinlong14（QL14）and denghai605（DH605）are drought-sensitive type;and the other three maize are moderate drought-resistant varieties.2.Drought reduced the relative water content（RWC）,net photosynthetic rate（Pn）,chlorophyll content（SPAD）and stomatal conductance（Gs）,and increased intercellar CO2concentration（Ci）of SD609 and SD902.It is indicated that the decrease in photosynthetic rate is caused by non-stomatal limitation.Compared with SD902,SD609 could maintain higher photosynthetic capacity,thereby increasing its recovery rate and degree after re-watering.3.Moisture changes could affect the photosynthetic electron transport efficiency of corn leaves.Under drought stress,the electron transport activity from the photosystem II（PSII）donor side to the photosystem I（PSI）receptor side decreased,and it was relieved after re-watering.Compared with SD902,SD609 can better coordinate the electron transfer between two photosystems,keep higher photosystem capacity,thus maintains the stability of the structure and function of the photosystems under drought and re-watering.4.The energy conversion of photosystems showed significant differences in two maize varieties in response to drought stress and re-watering.Drought leads to the accumulation of excess light energy in leaves of SD902,resulting in irreversible photoinhibition of PSII and PSI,which cannot be alleviated after re-watering;while in SD609,the excitation of cyclic electron flow（CEF）and non-photochemical fluorescence quenching Y（NPQ）could jointly protect PSII and PSI from damage and facilitate the recovery of photosynthetic capacity after re-watering.5.Moisture changes significantly affected the expression characteristics of photosynthetic genes in maize leaves.Drought stress induced markedly down-regulation of the expression of psbA,psbD and other photosynthetic related gene,and gradually recovered after re-watering.Compared with SD902,SD609 could maintain higher gene expression,and psaA,psaB which encoded PSI showed specific high expression.This indicating that SD609（drought-tolerant maize variety）could increase gene expression to enhance drought resistance under drought stress.In summary,the drought-tolerant maize variety SD609 has good photosynthetic potential.This is mainly attributed to its ability to maintain the integrity of photosynthetic structure and function,stimulate strong photoprotective mechanisms and increase gene expression under drought stress and re-watering.However,the photoprotective mechanisms and gene expression in SD902 showed lower level,which could not coordinate the electron transfer between two photosystems.These results lead to irreversible photoinhibition of photosystems and could not recover upon re-watering. |
