PHYSIOLOGICAL RESPONSES OF COFFEE TREE UNDER DIFFERENT IRRIGATION LEVELS

ABSTRACT The plant water potential and the leaf temperature are physiological responses of the coffee tree that can be used as indicative of the irrigation management of this crop. There is a dependence between the leaf water potential with the potential matrix of the soil solution, however, the water potential levels found for the coffee tree show divergent relationships in the literature regarding the matrix potential. The objective of this study is to verify the water potential and leaf surface temperature in the coffee tree when submitted to different irrigation levels. The study was conducted in Piracicaba, SP, Brazil, using Coffea arabica species from Red Catuaí IAC 144 variety, the drip irrigation system was adopted and the management done by tensiometry. The relationships among these physiological responses and the treatments of actions presented high determination coefficients (R2 of 0.84, 0.90 and 0.65 for the leaf water potential, leaf temperature measured with the portable infrared sensor and the thermal camera respectively). The estimated values for leaf water potential were −0.23, −0.56, −0.89 and −1.22 MPa for irrigation treatments L130%, L100%, L70% and L40%, respectively. The calculated leaf temperature values were 31.7, 32.4, 33.0 and 33.7°C in average, for treatments L130%, L100%, L70% and L40% in proper order.摘要 植物水势（plant water potential）与叶片温度（leaf temperature）是咖啡树的生理响应指标，可用于指示该作物的灌溉管理。叶片水势与土壤溶液基质势存在相关性，但现有文献中关于咖啡树测得的水势水平与基质势的关联关系存在分歧。本研究旨在验证不同灌溉水平下咖啡树的水势与叶面温度。 本试验于巴西圣保罗州皮拉西卡巴开展，供试材料为红卡杜艾IAC 144品种的阿拉伯咖啡（Coffea arabica），采用滴灌系统（drip irrigation system），并以张力计法（tensiometry）实施灌溉管理。 上述生理响应指标与各试验处理间的相关关系具有较高的决定系数（R²分别为0.84、0.90和0.65，对应叶片水势、便携式红外传感器测得的叶温、热成像相机测得的叶温）。 各灌溉处理L130%、L100%、L70%和L40%对应的叶片水势估算值依次为-0.23、-0.56、-0.89和-1.22 MPa。各处理的平均叶温依次为31.7、32.4、33.0和33.7℃。