Modulating seed reserve mobilization and antioxidant systems contributes to resilience to water stress in Mauritia flexuosa (Arecaceae) seedlings

Abstract Mauritia flexuosa is an Amazonian palm that has expanded its domains to the seasonal environment of the Cerrado biome. The species produces recalcitrant seeds, but the seedlings are tolerant to water deficit. Our objective was to evaluate the effect of water stress on post-germinative development in the species, focusing on dynamics of seed reserve mobilization and oxidative stress control. Seedlings were grown irrigated with water (Ψ w = 0 MPa) and under moderate (Ψ w = –0.9 MPa) and severe (Ψ w = –2.1 MPa) stress, for 30 days. Biometric, anatomical, histochemical and physiological evaluations (quantification of H 2 O 2 and MDA, histolocalization of O 2 − , evaluation of endo-β-mannanase and antioxidant system enzymes activities) were performed. The haustorium (cotyledonary blade) plays a central role in the resilience of seedlings to dehydration, as it adjusts its water potential to maintain water and nutrient absorption. In conditions of water deficit there is an accumulation of partially degraded (and unmobilized) reserves in the digestion zone, which favors water retention in the seed. Endo-β-mannanase activity increases in the endosperm adjacent to the embryo under moderate water stress. Also under moderate stress, root development is prioritized over the aerial part, which contributes to maintain a favorable water status. Seedlings present enzymatic and non-enzymatic antioxidant systems responsive to water stress (in the aerial part and haustorium), which help promote oxidative homeostasis. The resilience of M. flexuosa seedlings to water stress involves sophisticated adjustment in reserve mobilization patterns and the action of an efficient antioxidant system, which contribute to their reproductive success and adaptation to seasonality.