Trocas gasosas e estado hídrico em cacau consorciado e monocultivo sob diferentes lâminas de irrigação

Cacao is of major socioeconomic importance in the Trans-Amazonian region, where irregular rainfall may affect plant physiological performance. This study evaluated gas exchange and water status in seed-propagated cacao grown under intercropping and monoculture systems and subjected to irrigation levels corresponding to 0, 65, 100, and 130% of reference evapotranspiration. The experiment was conducted under field conditions using a split-plot design with five blocks. Leaf water potential (Ψf), net CO₂ assimilation rate (A), stomatal conductance (gs), intercellular CO₂ concentration (Ci), leaf transpiration (E), instantaneous water-use efficiency (WUE), and carboxylation efficiency (CE) were evaluated. During the rainy season, no significant differences in Ψf were observed among treatments, with values ranging from –0.17 to –0.55 MPa, indicating high water availability. During this period, plants grown in monoculture showed higher A, gs, and E due to greater availability of photosynthetically active radiation, whereas WUE was approximately 38% lower in monoculture cacao than in cacao grown in the intercropping system. During the less rainy season, increasing irrigation levels progressively increased Ψf, indicating mitigation of water stress. Mean Ψf was higher in the monoculture system (–0.75 MPa) than in the intercropping system (–1.07 MPa). These results indicate that irrigation is essential for maintaining plant water status during the less rainy season, whereas during the rainy season, the two cropping systems exhibit distinct responses associated with radiation availability and water-use efficiency.