| In order to explore the physiological mechanism of water stress affects on the grain yield of waxy maize,the pot trial was conducted at pot farm in 2014-2015.The hybrids were Suyunuo 5 and Yunuo 7,the control varieties of waxy maize national regional trials in Southern China.The water stress(drought or waterlogging)was imposed on flowering stage(tasseling to silking stage)and grain formation stage(about 15 days after pollination).The biomass accumulation and translocation,antioxidant system,phytohormones,photosynthesis,enzymatic activities that involved in the grain yield formation were studied.The main results are as follows.1 Grain yield and biomass accumulation and translocationThe grain number and weight were reduced by water stress at flowering stage and grain formation stage,which induced the grain yield loss.The grain yield loss at DW1(drought at flowering stage),WW1(waterlogging at flowering stage),DW2(drought at grain formation stage),and WW2(waterlogging at grain formation stage)was 15.15%,20.17%,27.35%,and 35.52%in Suyunuo 5,and was 11.95%,15.97%,21.70%,and 30.26%in Yunuo 7.This indicated that the decrease was serious under waterlogging than under drought,and plants were sensitive to water stress at grain formation stage.The grain dry weight was reduced by water stress at different stages.The grain water content was significantly decreased by DW1,DW2,and WW1,which under WW2 treatment was higher than the control before 21 DAP,whereas it was lower than the control after 21 DAP,indicated that the grain filling were suppressed under waterlogging.Water stress increased the rate of remobilization of pre-anthesis stored biomass in vegetative organs and contribution of pre-anthesis stored biomass to grain yield,while amount of remobilization of post-anthesis stored biomass in vegetative organs,contribution of post-anthesis photoassimilate to grain yield,and post-anthesis biomass accumulation were decreased.This indicated that the grain yield under water stress conditions was mainly dependent on pre-anthesis stored photoassimilates.2 The photosynthetic and fluorescentic charactersWater stress(drought or waterlogging)reduced leaf moisture content,stomatal conductance(Gs),transpiration rate(Tr),photochemical quenching coefficient(qP),inhibited leaf photosynthesis rate(Pn),actual photochemical efficiency(?PSII)and PSII photochemical efficiency(Fv/Fm),meanwhile increased intercellular CO2 concentration(Ci)and non-photochemical quenching coefficient(NPQ),the effect of waterlogging on photosynthetic parameters was greater than that of drought,and the effect of water stress on Suyunuo 5 was greater than that of Yunuo 7,which indicated that Suyunuo 5 was more sensitive to water stress.The result showed that the effect of water stress at grain formation stage on leaf photosynthetic and fluorescentic characters were higher than it imposed on flowering stage.After re-hydration,all indexes could be recovered to different degrees,and the plants that suffered water stress at flowering stage can recovered to control level.The results of correlation analysis showed that the grain yield was positively correlated with Pn,Tr,Chl a,Chl b and Car.However,water stress decreased the photosynthetic parameters such as Pn,NPQ and photosynthetic pigments in leaves,increased the concentration of Ci,and led to the grain yield loss.3 Antioxidant enzymes and osmotic regulatorsWater stress enhanced the activities of superoxide dismutase(SOD),peroxidase(POD),catalase(CAT)and production rate of O2-,and increased the contents of soluble protein,malondialdehyde(MDA),proline and soluble sugar in leaves and grains.The superior grain was less affected to water stress than that of the inferior grain.The activities of antioxidases and osmotic regulation substances were more sensitive to waterlogging than to drought,which can remove reactive oxygen more effectively,reduce the damage degree of cell membrane.Correlation analysis showed that the yield was significantly positively correlated with the contents of protein and soluble sugar,and the activities of SOD,POD and CAT,and negatively correlated with MDA,Pro,and O2-.4 Endogenous hormoneWaterlogging or drought stresses increased the content of ABA and ETH produce rate but decreased the content of GA3,Z+ZR and IAA in leaves and grains.And the inferior grains were more sensitive to water stress than that of superior grains.The influence of water stress at grain formation stage on plant endogenous hormones were severe than that of stress imposed at flowering stage.After re-watering,the parameters can recovered at a certain level,and the plant that had suffered water stress at flowering stage can recovered to control level.The effect of water treatment on Suyunuo 5 was significantly greater than that on Yunuo 7,which indicated that Suyunuo 5 was more sensitive to water stress.The results of correlation analysis showed that the yield was positively correlated with the contents of ABA,IAA and Z+ZR,and negatively correlated with the contents of GA3 and ETH in leaves and grains.Therefore,lower contents of GA3,Z+ZR and IAA and higher release rate of ETH under water stresses were the important reasons for the decrease of grain weight.5 Enzymes related to carbon and nitrogen metabolismWith plant growth,the activity of ADP-glucose pyrophosphorylase(AGPase)-and soluble starch synthase(SSS)in grains,sucrose phosphate synthase(SPS),sucrose synthetase(synthetic),glutamate synthase,glutamine synthetase,sucrose synthetase(cleavage)and sucrose content in leaves and grains increased first and decreased later.Meanwhile,starch content and AGP activity in leaves as well as nitrate reductase(NR)activity and protein content in leaves and grains decreased with grain filling,while starch content gradually increased.Drought or waterlogging reduced the contents of starch,sucrose and protein in leaves and grains,and the decrease was higher when plants suffered waterlogging.Drought and waterlogging significantly reduced the enzymatic activities related to starch synthesis,nitrogen metabolism,SPS and sucrose synthase(synthetic),but increased the activity of sucrose synthase(cleavage).The influence was highest at 9 DAP.Moreover,the effect of waterlogging on plants was significantly greater than that of drought stress.Plants were more sensitive water stress that imposed on grain formation stage than imposed on flowering stage.After rewatering,all indexes could be recovered to a certain degree,and the plants suffered water stress at flowering stage can recovered similar to the control level,while those suffered stress at grain formation stage could not recovered to the control level after 14 days of rewatering,and the recovery of waterlogging was less than that of drought,which indicated that water stress caused irreversible damage to plants.The results of correlation results indicated that the yield was positively correlated to the contents of starch,sucrose,activities of NR,GS,GOGAT,SPS,AGP,SSS and SBE in leaves and grains,which indicated that higher enzymatic activities related to starch sucrose synthesis were beneficial to increase nutrients and then improve grain yield in waxy maize production. |
PDF Full Text Request