GAS-EXCHANGE MEASUREMENTS ON MATURE, FIELD-GROWN GRAPEVINES BY WHOLE-CANOPY ENCLOSURE

An open-system, whole-canopy enclosure chamber for gas-exchange deter-minations was tested on three mature grapevines (Vitis vinifera L. 'Aglianico') during the summer of 2005. Data were measured by using an IRGA (Li-COR-840) and were collected automatically every 3 min using a CR23X datalogger mounted inside of the chamber. Temperature, leaf water potential and volumetric soil water contents were monitored at intervals. At harvest, canopy leaf area was about 9 m2. On 30 July, recent rainfall had restored soil water status to about 33% of soil volume (near field capacity). Under these conditions assimilation (A) and transpirations (T) showed mean daily values of 20 µmol s-1 and 7.5 mmol s-1 respectively and noon leaf water potentials were -1.1 MPa. By 13 August soil water content had fallen to 24% (close to wilting point), noon leaf water potential was -1.4 MPa and A and T showed values of 13 µmol s-1 and 2.5 mmol s-1 respectively indicating stressed conditions but with increased whole canopy water use efficiency. Gas-exchange data are comparable to values found in the literature for grapevine under stress condition and show that the new canopy chamber is an effective system for measuring the gas-exchange of mature vines in the field