| To reveal the regulation effect of root-sourced ABA to compensatory growth of spring maize after rehydration. Spring maize Jiudan 2 grown in pots experiment in greenhouse was subjected to five different treatments(well-watered and maintaining 75%~80% of maximum water holding capacity(CK)、moderately stressed and maintaining 50%~55% of maximum water holding capacity(MS)、severely stressed and maintaining 35%~40% of maximum water holding capacity(SS)、rehydration after moderately stressed (MS-CK)、rehydration afterseverely stressed(SS-CK)).The maize biomass, photosynthetic characteristics, root-sourced ABA concentrations and antioxidant enzyme activity were measured. The results showed that severe drought stress resulted in higher root-sourced ABA content of 80.15%, and significantly increased the activity of antioxidant enzymes SOD, POD, and CAT, by 85.48%, 72.67%, and 22.58%, respectively, but resulted in significant decrease of leaf stomatal conductance (Gs) and photosynthetic rate (Pn) by 51.56% and 12.16%, while the maximum Jmax, VCmax, TPU, and carboxylation efficiency (CE) of RuBP carboxylase decreased, which resulted in 46.56% decrease in the biomass per plant compared with normal water supply. After rewatering, the higher ABA content affected the recovery rate of cell membrane repairing and photosynthesis. Therefore, the biomass per plant increased by 90.36% compared with severe drought stress and increased by 1.73% compared with normal water supply, showing a compensatory effect. Moderate drought stress had a relatively lower ABA content of 23.53%, which resulted in increase of antioxidant enzymes SOD, POD, and CAT activity in leaves, by 64.72%, 41.72%, and 11.62%, respectively. That made the decrease in Gs and Pn relatively smaller by 15.01% and 6.42%, while Jmax, VCmax, TPU, and CE of RuBP carboxylase decreased less, which reduced the biomass per plant and decreased by only 13.64% compared to normal water supply. After rewatering, the relatively low ABA content in roots eventually increased the biomass per plant by 30.71% compared with moderate drought stress and increased by 12.88% compared with normal water supply showing a super-compensatory effect. In conclusion, the root-sourced ABA caused by drought stress plays a positive regulatory role in light absorption, photosynthetic carbon assimilation, and antioxidant protection on spring maize. |