No post-drought compensatory growth of corns with root cutting based on cytokinin induced by roots

The effect of shallow and deep roots on compensatory growth of potted corn seedlings during post-drought rewatering was investigated on the basis of leaf cytokinin induced by roots. Two treatment conditions, namely, root cutting and nitrate (NO3-) addition, were used in the study. Results showed that drought stress retained corn growth. In the absence of root cutting, rewatering increased the net photosynthetic rates of corn and induced compensatory growth. However, under root cutting, no compensatory growth occurred in the rewatered corns. In the absence of root cutting, significantly higher zeatin riboside (ZR) concentrations in the leaves and xylem saps were recorded under rewatering treatment than under wet treatment. However, these results were not observed under root cutting owing to loss of deep roots. Furthermore, corns with deep roots added with NO3- showed significantly higher ZR concentration in the leaves and xylem saps than those with shallow roots added with NO3-. High leaf cytokinin concentration is known to induce rapid corn growth. Thus, no compensatory growth occurred during post-drought rewatering in corns with few deep roots, likely due to lack of leaf cytokinin enhancement induced by deep roots.