Stressed mothers, tolerant daughters: a case study about the physiological responses and growth of sugarcane plants under water deficit
Drought stress can imprint marks in plants after a previous exposure, leading to a permissive state that facilitates a more effective response to subsequent stress events. Such stress imprints would benefit plants obtained from progenitors previously exposed to drought. Herein, our hypothesis was that daughter plants obtained from mother plants previously exposed to water deficit will perform better under water deficit as compared to those obtained from mothers that did not face stressful conditions. Sugarcane mother plants were grown under well-hydrated conditions or subjected to three cycles of water deficit by water withholding. Then, daughter plants produced through vegetative propagation were subjected to water deficit. Leaf gas exchange was reduced under water deficit and daughters from mothers that experienced water deficit presented a faster recovery of CO2 assimilation and higher instantaneous carboxylation efficiency after rehydration as compared to daughters from mothers that did not face water deficit. Plants obtained from mother plants that faced water deficit showed the highest leaf proline concentration under water deficit as well as higher leaf H2O 2 concentration and leaf ascorbate peroxidase activity regardless of water regime. Under well-watered conditions, daughters from mothers that faced stressful conditions presented higher root H2O2 concentration and root catalase activity than ones from mothers that did not experience water shortage. Such physiological changes were associated with improvements in leaf area and shoot and root dry matter accumulation in daughters from stressed mothers. Our results suggest that root H2O2 concentration is a chemical signal associated with stress memory and improved sugarcane growth. Such findings bring a new perspective to sugarcane production systems, in which stress memory can be explored for improving drought tolerance in rainfed areas.