Phosphate starvation response precedes drought response in field-grown plants
Drought severely damages crop production, even under conditions so mild that the leaves show no signs of wilting. As effective methods for analyzing the field drought response have not been established, it is unclear how field-grown plants respond to mild drought. We show that ridges are a useful experimental tool to mimic mild drought stress in the field. Mild drought reduces inorganic phosphate levels in the leaves to activate the phosphate starvation response (PSR) in field-grown soybean plants. PSR-related gene expression is mainly observed under drought conditions that are too mild to activate abscisic acid-mediated gene expression. Thus, our study provides insights into the molecular response to mild drought in field-grown plants and into the link between nutritional and drought stress responses in plants.