Abstract
Drought stress can imprint marks in plants after a previous exposure, leading to plant acclimation and a permissive state that facilitates a more effective response to subsequent stress events. Such stress imprints would benefit plants obtained through vegetative propagation (propagules). Herein, our hypothesis was that the propagules obtained from plants previously exposed to water deficit would perform better under water deficit as compared to those obtained from plants that did not face stressful conditions. Sugarcane plants were grown under well-hydrated conditions or subjected to three cycles of water deficit by water withholding. Then, the propagules were subjected to water deficit. Leaf gas exchange was reduced under water deficit and the propagules from plants that experienced water deficit presented a faster recovery of CO2 assimilation and higher instantaneous carboxylation efficiency after rehydration as compared to the propagules from plants that never faced water deficit. The propagules from plants that faced water deficit also showed the highest leaf proline concentration under water deficit as well as higher leaf H2O2 concentration and leaf ascorbate peroxidase activity regardless of water regime. Under well-watered conditions, the propagules from plants that faced stressful conditions presented higher root H2O2 concentration and higher activity of catalase in roots as compared to the ones from plants that did not experience water shortage. Such physiological changes were associated with improvements in leaf area and shoot and root dry matter accumulation in propagules obtained from stressed plants. Our results suggest that root H2O2 concentration is a chemical signal associated with improved sugarcane performance under water deficit. Taken together, our findings bring a new perspective to the sugarcane production systems, in which plant acclimation can be explored for improving drought tolerance in rainfed areas.
Highlights
As a semi-perennial species, sugarcane plants face seasonal drought under field conditions, where water deficit causes reduction in photosynthesis and accumulation of carbohydrates, changes in antioxidant metabolism, and impairment of plant growth and sucrose yield [1, 2]
The origin plants were subjected to three cycles of water deficit and leaf gas exchange was measured during the dehydration and rehydration stages (S1 Fig)
The propagules were placed in plastic boxes with nutrient solution and four treatments were done after 18 days: the propagules from plants grown under well-watered conditions maintained under well-watered conditions (W/W) or subjected to water deficit (W/D); and the propagules from plants grown under cycles of water deficit maintained under well-watered conditions (D/W) or subjected to water deficit (D/D)
Summary
As a semi-perennial species, sugarcane plants face seasonal drought under field conditions, where water deficit causes reduction in photosynthesis and accumulation of carbohydrates, changes in antioxidant metabolism, and impairment of plant growth and sucrose yield [1, 2]. Recurrent cycles of drought followed by rehydration are known to improve plant performance during a new stressful event [3,4,5]. Such phenomenon indicates that plants are able to change their metabolism and growth after an external stimulus, improving recovery or resilience of photosynthesis, increasing water use efficiency [4] and photoprotection [6] and reducing the negative impact of drought on yield, i.e. increasing resistance [7]. The physiological acclimation permits plants to overcome resource limitation, improving tolerance while impairing plant growth [8]. While increased activity of antioxidant enzymes would permit a faster and more effective control of stress-induced production of reactive oxygen species [11], lower stomatal conductance due to accumulation of abscisic acid could reduce water consumption and improve water balance under drought without impacting photosynthetic rates [5]
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