Physiological and Biochemical Responses of Robusta Coffee to Water Deficit under Field Conditions

The sustainability of Coffea canephora cultivation in regions prone to water stress depends on the selection of cultivars adapted to water management conditions and environmental variability. This study aimed to evaluate the physiological and biochemical parameters of robusta coffee cultivars under different soil water tensions. The experiment was conducted in a split-plot design, combining five soil water tensions (20 kPa, 40 kPa, 60 kPa, 100 kPa, and no irrigation) and six robusta coffee cultivars (BRS 1216, BRS 2299, BRS 2314, BRS 3210, BRS 3213, and BRS 3220), allocated as main plots and subplots, respectively. The experimental design was randomized blocks with three replicates. Over two years, plants in the growth (2021) and production (2022) phases were evaluated for gas exchange, chlorophyll-a fluorescence, membrane damage, relative water content, and levels of photosynthetic pigments andmetabolites. Non-irrigated young robusta plants exhibited lower photosynthetic rate (A) and transpiration (E), along with reduced stomatal conductance (gS). The photochemical efficiency of PSII and energy dissipation mechanisms, except for NPQ, were also lower without irrigation. Soluble carbohydrate levels were negatively correlated with photosynthesis. During the growth phase, cultivars BRS 1216 and BRS 3210 showed higher photosynthetic productivity, while BRS 2314 had the lowest. It was concluded that stomatal regulation and light absorption adjustments in PSII, through reductions in Fv/Fm and photosynthetic pigment levels, are key mechanisms in robusta coffee plants to mitigate water stress damage. Additionally, the cultivars maintained photosynthetic performance under high soil water tension, suggesting their suitability for cultivation under low irrigation levels. Key words: Coffea canephora; Robustas Amazônicos;Water deficit; Irrigation.