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 本研究通过测定植物蒸腾速率与叶片温度，可为果园灌溉时机与灌溉量的确定提供依据。本研究旨在测定有、无水分胁迫条件下巴西锥果木（Caryocar brasiliense Camb.）的叶片温度与树干液流速率。此外，本研究采用红外测温法采集叶片温度数据，并通过Granier法（Granier method）估算蒸腾速率，该方法需将热消散探针（thermal dissipation probes）插入植物茎干。本试验在巴西戈亚斯州戈亚尼亚市的一处种植120株果树的果园内开展，选取其中7株树龄为6.6~7.4年的植株（3株灌溉组、4株非灌溉组）进行了为期8个月（2015年10月至2016年5月）的观测。试验土壤为贫瘠红色砖红壤，采用EC-5电容传感器测定土壤含水量。研究结果显示：在夏季与旱季过渡期，灌溉组植株的叶片温度低于同期空气温度中位数；非灌溉组植株在旱季则出现水分亏缺。在雨养条件下，植株平均蒸腾速率为24.09升·株⁻¹·天⁻¹，灌溉后该值提升至42.29升·株⁻¹·天⁻¹。