Abstract
We present the measurement and modelling of transpiration from squash (Cucurbita maxima Duchesne) growing in the field under a tropical maritime climate. Measurements were carried out on Tongatapu (175°12′ W, 21°08′ S), a coral atoll located in the Pacific Ocean. Transpiration was determined from heat-pulse measurements of sap flow in the vine stem using the T-max method. Steady-state porometry was used to monitor stomatal conductance (gS, mm s−1). The data were used to derive parameters for a functional model of conductance that includes response functions for light, air temperature and vapour pressure deficit of the air, and a novel response function for soil moisture. Leaf area development was monitored through the growing season using a point quadrant approach. The maximum leaf area was about 2.7 m2 per plant and the effective ground area was about 1 m2 for each plant. Transpiration losses were calculated using a 2-layer big-leaf model in combination with modelled stomatal response and measured leaf area. In general, the sap flow measurements were in good agreement with the calculations of plant water use. Peak water use was between 3 and 5 L per plant per day. Daily transpiration measurements from heat-pulse were used to derive a crop factor, KC, for squash in this tropical maritime climate. The derived seasonal pattern of KC was similar to the FAO recommended crop factor for squash. However, the growing season was a little shorter. Measured sap flow also revealed periods of short-term drought and leaf fungal disease that reduced the actual transpiration losses, and there was often a rapid recovery from water stress following rainfall events.
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van der Velde, M., Green, S.R., Vanclooster, M. et al. Transpiration of Squash Under a Tropical Maritime Climate. Plant Soil 280, 323–337 (2006). https://doi.org/10.1007/s11104-005-9504-y
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DOI: https://doi.org/10.1007/s11104-005-9504-y