Wines & Vines

June 2014 Enology & Viticulture Issue

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p r a c t i c a l w i n e r y & v i n e ya r d J U n e 2 0 1 4 61 g r a p e g r o w i n g ScareWindmill To birds windmill looks like a flock of birds taking off in fright. New improved lock system to keep blades from coming loose 36" dia. blades that repel birds in one or more acre area. Effective for birds in vineyards, fruit trees, and blueberries. Effective on wild turkeys & geese too 30 day unconditional money back guarantee. $89 JWB Marketing (800) 555-9634 birddamage.com growth and refill cavitated xylem con- duits to maintain plant hydraulic conduc- tivity. However, E night is not coupled with photosynthesis, and this contributes to decreased WUE. Plants have different strategies to respond to water stress, and these influ- ence shape and dimensions of the para- bolic curve presented in Figure 1. In general, for horticultural plants it is con- sidered Ö = -1.0 MPa as a threshold between non-water stress and water- stressed plants. 17,22,24 Grapevine cultivars that are more con- servative in water use (isohydric) tend to show a displacement of the parabolic curve to the right, closing stomata at night with higher Ö s measured the previ- ous day. Non-water conservative grape- vine cultivars (anisohydric) present peaks shifted toward the left of -1.0 MPa in the parabolic relationship (Fuentes et al., under review). There is an opportunity for adaptation strategies, in the case of grapevines, defined first by cultivar selection and, second, by management strategies through reduced or controlled water application that will help minimize E night and maximize rehydration and WUE. Implication of nighttime transpiration on modeling and water footprint estimations I n general, evapot ra n spi rat ion (ET) models do not take nighttime water uptake into consideration for small- scale calculations (irrigation schedul- ing) or larger scale (global modeling). The main problem to account for this pr ev iou sly u n s e e n fac tor wa s t he requirement of accurate instrumenta- tion to record low flows. The micrometeorological approach (Bowen ratio, Eddy covariance) has been the most used method to validate ET models in crops and forests. However, low wind velocity and the lack of eddies at night makes it difficult to account for low flows using these techniques. The alternative could be the use of lysimeters, which are sensitive enough to register flows at night. However, it is not possible to uncou- ple transpiration from evaporation of water directly from the soil using the latter. It is important to notice that E night will be associated with water extraction by deeper roots and likely that these methodologies to estimate ET and water footprint need to be revisited. Conclusion There is significant value in understand- ing and characterizing the dynamics of nighttime water uptake and transpiration processes by plants and trees to obtain insights into the adaptation strategies that will contribute to increased WUE in a climate-change scenario. Further research is required to understand the differences in strategies according to different species and cultivars. Modeling and water footprint method- ologies need to be revisited in light of the latest research about nighttime water consumption and transpiration by plants and trees. PWV Edited and reprinted from Wine & Viticul- ture Journal July/August 2012 with Approval of the publisher, Winetitles. Bibliography l. Bauerle, W.L., T.H. Whitlow, T.L. Setter, and F.M. Vermeylen. 2004 "Abscisic acid synthesis in Acer rubrum L. leaves – A vapor-pressure- deficit-mediated response." J. of Amer. Society for Horticultural Science 129 (2): 182–187. 2. Caird, M.A., J.H. Richards, and L.A. Donovan. 2007 "Night-time stomatal conductance and transpiration in C3 and C4 plants." Plant Physiol. 143 (1): 4–10. Napa Fermentation Supplies is proud to be the West Coast Kärcher distributor. Our prices are the lowest and we have the complete product line available. We are also a Kärcher repair facility. Kärcher state-of-the-art high-pressure washers are distinguished by infinitely variable operating pressure, water volume and temperature control, as well as precise chemical metering. Heated models incorporate a 90%+ fuel efficient burner system, low fuel shut-off and complete machine shut-off at the trigger gun for maximum safety and performance. NAPA FERMENTATION SUPPLIES Napa Fermentation Supplies (707) 255-6372 • napafermentation.com

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