LEAF TEMPERATURE AND TRANSPIRATION OF PEQUI TREES WITH AND WITHOUT WATER RESTRICTION

ABSTRACT The answers to when and how much to irrigate orchards can be obtained based on the measurements of plants' transpiration and leaf temperature. This study aims to determine the leaf temperature and sap flow of the pequi tree (Caryocar brasiliense Camb.), both with and without water restriction. Further, the leaf temperature was measured by infrared thermometry and estimated transpiration using the Granier method, where the thermal dissipation probes are inserted into the plant stems. The experiment was conducted in a 120-plant orchard located in Goiânia-GO, Brazil, from which seven of the plants (3 irrigated and 4 non-irrigated; aged 6.6–7.4 years) were evaluated for eight months (October 2015 to May 2016). The soil was characterized as a dystrophic red latosol, and its water content was determined using the EC-5 capacitance sensors. The results denoted that the leaf temperature of the irrigated plants was lower than the median air temperature during summer and the transition period into the dry season, and the non-irrigated plants exhibited shortage of water availability during the dry season. In dryland conditions, the average transpiration was 24.09 L plant−1 day−1 and, when irrigated, became 42.29 L plant−1 day−1.

摘要
本研究旨在通过监测植物蒸腾量与叶片温度，确定果园灌溉的时机与灌溉量。具体而言，本研究旨在测定佩基果（pequi tree，Caryocar brasiliense Camb.）在有无水分限制条件下的叶片温度与树干液流。此外，本研究采用红外测温法测定叶片温度，并通过Granier法估算蒸腾量——该方法需将热消散探针（thermal dissipation probes）插入植物茎干内。
本实验设于巴西戈亚斯州戈亚尼亚市的一处含120株植株的果园中，选取其中7株树龄为6.6~7.4年的植株（3株为灌溉组，4株为非灌溉组）开展为期8个月（2015年10月至2016年5月）的监测。试验土壤为贫瘠性红色砖红壤，土壤含水量通过EC-5电容传感器测定。
结果表明：夏季及旱季过渡期内，灌溉组植株的叶片温度低于同期空气温度中位数；而非灌溉组植株在旱季出现水分亏缺。雨养条件下植株平均蒸腾量为24.09升·株⁻¹·天⁻¹，灌溉后该值提升至42.29升·株⁻¹·天⁻¹。