Determination of transpiration in irrigated grapevines: comparison of the heat-pulse technique with gravimetric and micrometeorological methods |
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Authors: | I. A. M. Yunusa R. R. Walker B. R. Loveys D. H. Blackmore |
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Affiliation: | (1) CSIRO Plant Industry, Merbein Laboratory, Private Bag, Merbein, Vic 3505, Australia, AU;(2) CSIRO Plant Industry, Glen Osmond, SA 5064, Australia, AU |
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Abstract: | The use of a heat-pulse technique to monitor sap flow from which transpiration can be deduced was evaluated in ungrafted grapevines (Vitis vinifera L., cv. Sultana) under glasshouse and field conditions. There was a significant degree of agreement between daily transpiration deduced from heat-pulse velocity (T hp) and that determined directly by gravimetry in the glasshouse and by calibration using the Penman-Monteith equation in the field. Comparison throughout the growing season of T hp to transpiration calculated with the full Penman-Monteith equation produced a high coefficient of determination (r 2=0.69). A similar comparison of T hp with transpiration calculated with only the aerodynamic component of the Penman-Monteith equation produced a non-linear relationship, due to the equation over-estimating transpiration relative to T hp at high vapour pressure deficits (i.e. above 2.5 kPa). Values for total seasonal transpiration measured with heat-pulse sensors or calculated with either the full Penman-Monteith equation or with only the modified aerodynamic component of the equation were within 10% of each other. Transpiration (T hp) in grapevines with an adequate supply of soil water was shown to be coupled to ambient air conditions. Received: 20 July 1998 |
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