Gas exchanges and chlorophyll fluorescence of young coffee plants submitted to water and nitrogen stresses

摘要

This research aims to evaluate the impact of nitrogen deprivation and water stress on gas exchange and chlorophyll fluorescence in young plants of five cultivars of Arabic coffee. A factorial experiment 5 (cultivars) x 3 (treatments: control without stress, water stress of -1.5 MPa and stress of N - 0.0 mmol L-1N) was carried out in a complete randomized block design with three replicates. Before being submitted to the treatments, the plants were grown in a greenhouse for 240 days, and then transferred to a growth chamber under controlled conditions. Subsequently, after the experimental period of 96 h we measured photosynthetic rate (A), stomatal conductance to water vapor (g(s)), transpiratory rate (E), internal and external carbon ratio (Ci/Ca), water use efficiency (A/E), electron transport rate (ETR), actual quantum yield of PS II electron transport (phi FSII), and maximum photochemical efficiency of PS II (Fv/Fm). Water stress reducedA,g(s),E,A/E, ETR, phi FSII, andFv/Fm. The nitrogen deficiency reduced ETR, phi FSII, andFv/Fm. Under short-term water stress Catuai Vermelho maintain theAvalues due to better stomatal control, reduced water lost by transpiration (E) and better water use efficiencyA/E, while Mundo Novo and Acaua show lower damage toFv/Fm. Short-term nitrogen stress has low impact onAof young plants ofCoffea arabicacultivars with adequate N-nutrition.