ARS | Publication request: MOBILE CHAMBER SYSTEM FOR FIELD MEASUREMENTS OF WHOLE-VINE PHOTOSYNTHESIS

Submitted to: American Journal of Enology and Viticulture
Publication Type: Abstract
Publication Acceptance Date: April 15, 2003
Publication Date: December 15, 2003
Citation: Perez Pena, J., Tarara, J.M. 2003. Mobile chamber system for field measurements of whole-vine photosynthesis. American Journal of Enology and Viticulture.

Technical Abstract: Six flow-through chambers (8m^2 volume) were built for the measurement of gas exchange (CO2 and H2O) from whole vines under deficit meant to impose water stress at different stages of berry growth. Chamber design criteria and materials used were selected to minimize the chamber effect and to accommodate the trellis of a mature, field-grown vine. A framed design allowed the chambers to withstand sustained winds up to 13 m/s, overcoming one disadvantage of the balloon-type chambers. The effects of the enclosure, the "chamber effect," was quantified. At canopy height, air temperature was no more than 2.5 degrees C higher than at the same height in an unchambered canopy. Over 24 h, solar radiation inside the chamber was 90% of ambient. For vines irrigated according to standard industry practice, maximum values of net CO2 exchange approached 15 umol/m^2/s^1, whereas in deliberately water-stressed vines the maxima approached only 10 umol/m^2/s^1. Likewise, the chamber system detected a reduction in transpiration among water stressed plants, where maximum rates averaged 2 mmol/m^2/s^1 as opposed to vines under standard irrigation, at 4 mmol/m^2/s^1. Apparent light saturation for canopy photosynthesis was approximately 1200 umol/m^2/s^1 PPFD (photosynthetic photon flux density) for vines under standard irrigation, and about 800 umol/m^2/s^1 for vines under additional water stress.