Study On The Drought Sensitivity And Recovery Ability Of Different Genotypic Maize Under Cyclical Drought And Rewatering

The cyclical drought and rewatering has been occurred frequently in summer maize growing period,which has been significantly influenced the growth and development of summer maize in Huang-huai-hai Plain of China.A pot and micro-field experiment has been conducted to explore the morphological,physiological and biochemical responses of maize under the drought-rewatering environment with seven maize hybrids of Henan province in seedling stage and tasseling stage in May-July 2017 and June – October 2018 respectively,by which to illustrate the sensitivity and resilience of different maize varieties under different growth stage,stress duration and drought-rewatering cycles.The results had been showed below:1、Drought stress in seeding and tasseling stage inhibited plant growth and accelerated leaf senescence and shedding.The growth rate increased after re-watering but it can’t offset the impact of drought stress.In the flowering stage,vegetative growth was less affected by drought stress,and there was no significant difference in plant height between the treatment groups and control.The decrease of leaf area was mainly reflected in the shedding of bottom leaves,and the leaf dry weight was significantly lower than the control.Chlorophyll synthesis was blocked and the leaf water content was decreased in drought stress.When the successive drought lasted 2days(reached to 40%FC),chlorophyll content in maize leaves was less affected but decreased significantly after the drought lasted 4 days(reached to 25%FC).Chlorophyll content has increased in ZD958 and XD29 because of the decrease of leaf expansion.All of these changes can be recovered equal to the control after rewatering.Carotenoids in leaves were less responsive to short period stress but significantly higher than control in long period of drought,and the recovery degree of carotenoids varied with the varieties.2、The photosynthetic characteristics under drought stress were mainly regulated by stomatal factors.The Fv/Fm was less affected by soil water condition and it can be recovered quickly after rewatering.The Pn,Gs and Tr of was gradually decreased within successive drought.The rate of decline was faster when the drought lasted 2days to 3 days(about 30%-40%FC),and it reached to the lowest value when the drought lasted 4 days(reached to 25%FC).The Pn and Gs increased rapidly after rewatering for 1 day(reached to 70%FC),and the Tr increased rapidly in 2d-3d(maintained at 70%FC for 1-2d).The photosynthesis recovered to the control level after 3 days(70%FC)of rewatering.3、 Osmotic adjustment system was sensitive to water stress,which is mainly dominated by proline regulation in maize.The osmotic potential of maize leaf decreased gradually with the duration of drought stress,while the proline accumulation was on the contrary,and they were not completely recovered after rewatering,which showed a high osmotic regulation ability.The accumulation of soluble protein content was varied under drought stress within material and drought intensity.It increased after the drought lasted 2 days(40%FC)and decreased after the drought lasted 4 days(25%FC).4、MDA content increased with leaf senescence and decreased gradually after rewatering.The activity of antioxidant enzymes: SOD and POD were less responsive under the drought lasted 2 days(40%FC).With the extension of stress duration,it was significantly higher than that of the control group,and the activity of antioxidant enzyme in ZD958 and XD29 were lower than that of the control group under severe drought,which mainly owing to the enzymatic inactivation of protein decomposition under severe drought conditions.SOD activity recovered to the control level,while POD had the lower resilience after rewatering.5、Under drought stress,abscisic acid(ABA)and auxin(IAA)were significantly increased,which regulated stomatal closure to delay leaf senescence,thereby enhanced plant drought resistance,and it decreased to the control level after rewatering.Gibberellin(GA)and maize nucleoside(ZR)were irresponsive in flowering period,and no obvious change had been found in drought and rewatering.6、Multiple drought-rewatering cycles induced a stress prints in maize.When they subjected to stress again,due to the "stress memory",maize would change its response to drought in response speed,degree and recovery ability.Moreover,maize adapt to environment after multiple drought and rewatering was manifested as two-sided.The results of this study showed that repeated drought and rewatering enhanced the adaptability of the photosynthetic system in the second cycle of drought,which mainly reflected in increasing the range of threshold in photosynthetic capacity,faster recovery rate and stronger recovery ability after rewatering.Osmotic regulation system and antioxidant system were more sensitive to water stress after pre-drought rehydration.In addition,the water consumption of plants in the second cycle was significantly lower than that in the first cycle.7、The results of heat map analysis showed that osmotic regulation system responded to water stress early and sensitively,while photosynthetic system and antioxidant system changed less under slight drought and more under severe drought.After rewatering,the leaf water content and photosynthetic system recovered rapidly,and the osmotic regulation system and antioxidant enzyme system remained active.For 7 maize hybrids,LY35 and WK702 were insensitive to soil water content,while XD29 and XY335 were sensitive to soil water environment.After rewatering,WK702,ZD958 and DH605 had strong recovery ability,while WG704 and XD29 were the opposite.