Selênio (se) e silício (si) na atenuação de estresse hídrico no desenvolvimento inicial do cafeeiro (Coffea Arabica)

Abstract

Plants are constantly exposed to abiotic stresses, resulting from high temperatures and irregular rainfall distribution, negatively affecting agriculture, especially sensitive crops such as Coffea arábica. The aim of this study was to evaluate the effects of silicon (Si) application via soil combined with selenium (Se) doses via foliar application in the attenuation of water stress in Coffea arabica plants grown up to 280 days after transplanting (DAT). The study was conducted in a greenhouse at the Department of Soil Science at UFLA, from December 2022 to November 2023. Two simultaneous experiments were installed, each in a completely randomized experimental design, with three replicates. Si applications at doses of 35 and 70 mg kg-1 were tested at 85 DAT in both experiments, combined with Se at doses of 5, 10 and 20 g ha-1at 95 DAT for experiment No. 1 and 240 DAT for experiment No. 2, plus a control (without Se and Si doses) in each experiment. The stress period lasted 20 days, starting at 255 DAT, and initially the available water in the soil was reduced to 60% for 10 days (humidity monitored with the Teros 11 sensor), and then to 50% for another 10 days. After this period, the plants were rehydrated for 5 consecutive days. Evaluations were carried out at two moments (maximum stress and rehydration) with readings of photosynthesis, stomatal conductance and transpiration; the percentage of relative water content in the leaves was also determined. At the end of the experiment (280 DAT), the nutritional value of Se and Si, as well as other macro and micro nutrients, was evaluated. The dry mass of the aerial part and root was also determined, at which time a leaf sample was separated to evaluate the isotopic composition of carbon thirteen (δC13). The Se contents in the plant tissues ranged from 2.35 to 4.92 mg kg-1 for the application time of 95 DAT and from 2.84 to 4.21 mg kg-1 for 240 days DAT. The values for Si ranged from 7.02 to 9.12 g kg-1. Plants that received the dose of 70 mg kg-1 Si combined with 5 g ha-1 Se at 95 DAT showed a gain of 30.8% in MSPA and 34.35 in MSR, also showing a higher photosynthetic rate (3.13 μmol CO2 m-2s-1). Coffea arábica plants showed δC13 values between -25.97 and -27.78 ‰. It is concluded that applying doses of 35 mg kg-1 Si combined with 5 g ha-1 Se applied in advance (95 DAT) to the water deficit period can improve coffee tolerance, favoring its growth and increasing its resistance. These results are promising for mitigating the negative impacts of climate change on coffee production. Furthermore, it was observed that the lower concentration of Si and Se in leaf tissues is associated with greater tolerance in Coffea arabica, indicating a potential way to optimize management practices aimed at the climate adaptation of plants.