Sugarcane Resilience to Recurrent Water Deficit is Dependent on the Systemic Acclimation of Leaf Physiological Traits

Sugarcane cultivation area is exposed to irregular rainfall which leads to several water deficit events during crop development. The plants have the ability to promote physiological and morphological changes to face water deficit. It is probable that, in sugarcane, higher tolerance to recurrent water deficit events is caused by physiological adjustment after the first water deficit exposure. We tested the hypothesis that previous exposition to water deficit event increase drought tolerance of sugarcane in a second water deficit event. Our study was carried out with genotypes RB72454 (drought-susceptible) and RB867515 (drought-tolerant) submitted to two water conditions: control and two events of water deficit (WDE1 and WDE2), separated by a rehydration event (RE). Sugarcane genotypes under WDE1 decreased pre-dawn and mid-day water potential (Ψmd and Ψpd), photosynthesis (A), stomatal conductance (gs), electron transport rate (ETR), and increased intercellular CO2 concentration (Ci), when compared to control conditions. Contrastingly, sugarcane genotypes under WDE2 displayed smaller decrease in A, due to higher ETR, as compared to WDE1. The Multivariate Plasticity Index (MVPi), showed that sugarcane genotypes displayed high physiological plasticity in WDE1, being even higher in the drought-tolerant genotype than in the drought-susceptible one. In WDE2, sugarcane presented a decrease in physiological plasticity. Thus, higher physiological plasticity in WDE1 indicated that water deficit affected plant homeostasis, causing an impact in physiological traits, whereas the lower physiological plasticity showed in WDE2 is possibly related to sugarcane acclimation to water deficit, with a less prominent impact in physiological traits.