Date Published: June 28, 2018
Publisher: Public Library of Science
Author(s): Xiao-Ling Wang, Rong-Rong Qin, Run-Hong Sun, Xiao-Gai Hou, Lin Qi, Jiang Shi, Jinxing Lin.
The effect of plant population density (PPD) and root-induced leaf cytokinin on the compensatory growth of potted corn seedlings during post-drought rewatering was investigated. The study design comprised four treatments: (1) wetness with low PPD, (2) wetness with high PPD, (3) rewatering with low PPD, and (4) rewatering with high PPD. Results showed that drought stress restrained the growth of corns. By contrast, rewatering enhanced the net photosynthetic rate and growth of corns. During the 8 days of rewatering, compensatory growth during post-drought rewatering occurred in corns with high PPD; however, such compensatory growth did not occur in corns with low PPD. Zeatin riboside concentrations in leaves and xylem saps were significantly higher under rewatering treatment than those under wet treatment. High leaf cytokinin concentration accelerated corn growth. The coefficients of variation and Gini-coefficient of wet treatment were significantly higher than those of rewatering treatment under high PPD, demonstrating that intense intraspecific competition occurred in the wet treatment. Extreme intraspecific competition negatively affected net photosynthetic rate. In brief, the interactions between root-induced leaf cytokinin and weak intraspecific competition promoted the compensatory growth under high PPD.
Plant compensatory growth theory during post-drought rewatering underlies the extensive application of water-saving agriculture techniques, which mostly involve regulated deficit irrigation, deficit irrigation technologies, and dryland agriculture [1–5]. Compensatory growth is defined as the increase in plant growth rate in response to water availability after drought. The mechanism of compensatory growth during post-drought rewatering has been investigated in numerous crops, including maize, wheat, Kentucky bluegrass, and cotton [6–9]. Photosynthetic rate, stomatal conductance, fertiliser use, anti-aging properties, and other attributes show close association with compensatory growth. Crop production is essentially controlled by plant population density (PPD). However, the population-level mechanism underlying crop compensatory growth during post-drought rewatering remains poorly understood and thus warrants further investigation.
In this study, drought stress inhibited corn seedling growth, whereas rewatering increased corn growth. Rewatering caused a larger increase in net photosynthetic rate under high PPD than under low PPD. During 8 days of rewatering, compensatory growth during post-drought rewatering easily occurred in high PPD corn, whereas no compensatory growth was observed in low PPD corn. Rewatering also increased ZR concentrations in leaves and xylem saps, and high leaf cytokinin concentration increased corn growth. Compared with wet corns, rewatered corn showed less intraspecific competition under high PPD, thereby benefiting increased growth and photosynthetic rate. The interaction of leaf cytokinin induced by roots and weak intraspecific competition caused compensatory growth to occur easily under relatively high PPD.