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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 59 g r a p e g r o w i n g photorespiration. In these conditions, WUE is expected to increase, since more CO 2 will also decrease stomatal conduc- tance by about 20%. 8 In the past, it was a general consensus that C3 and C4 plants closed stomata at night. Any nocturnal water uptake would mainly correspond to stem and organ rehydration and cuticular transpiration. Under these conditions, WUE is not affected by nocturnal water uptake, which only corresponds to plant recovery from water stress endured the previous day. However, new research has demon- strated that nocturnal transpiration (E night ) due to stomatal opening at night (G night ) can be as high as 30% – 60% com- pared to diurnal transpiration for arid and semi-arid regions in a variety of eco- systems. 2,9,11,19,20,23,25 Considerable E night has significant implications for the whole-tree water budget and WUE. Recent studies have characterized nighttime water uptake (S n ) dynamics using sap-flow sensors and gas-exchange measurements and have offered insights into the relationship between nighttime transpiration (E night ) and rehydration. Literature review/recent research Sensitive sensors can pick up nighttime water flow Sap-flow probes used in the past were not sensitive to low flow (typically during nighttime) and gave "noisy" data that added to the paradigm of stomatal closure during the night and led scientists to dis- regard nighttime sap-flow values and force them to zero for analysis. However, continuous measurements of sap flow using probes sensitive to low flow has been possible in the past 10 years through the compensated heat- pulse sap-flow system. 10,11,12,13,14,15 Figure 1 shows the total S n measured during nighttime (from sunset to sunrise) by the sap-flow sensors. The total S n response to water application (either by irrigation or rainfall) shows that S n is sen- sitive to the dynamics of soil-water avail- ability and plant-water status associated with the previous day. Similar results have been obtained for grapevines (Fuentes et al., submitted). Parabolic relationships between S n and plant-water status Factors such as hormonal signals, mainly abscisic acid (ABA), are related to lower diurnal stomatal conductance (G s ) at increased levels of water stress. 1,3,4,6,7,16 This has been the basis for the development of irrigation techniques such as RDI and PRD that help to increase WUE. Based on the hypothesis that the same internal factors affecting G s (ABA) will affect G night , it is expected that the latter will be responsive to the level of water stress endured by the plant or tree the previous day that can be measured as stem-water potential (Ös) using a pres- sure chamber. 5,21 Recent research has shown a parabolic relationship between S n and Ös measured the previous day for a variety of crops and fruit trees such as almonds, 11 grape- vines (Fuentes et al., under review) and citrus trees (Fuentes et al., unpublished). Figure 2 shows the relationship from which two areas can be identified: non- water stress conditions to mild water- stress conditions (0 > Ös > -1.0 MPa [megapascals]), and from mild water- stress conditions to severe water-stress conditions (-1.0>Ös > -2.5 MPa). The peak of this relationship corresponds to the maximum S n . Physiological data helps explain nighttime behavior Since S n data is obtained using sap-flow sensors inserted in the trunk, it is not pos- "After the horrible 2004 season, with many vineyards getting little or no grapes, a 3 acre section of Reisling yielded 20 tons. Without the Mega PRO, we would have lost $20,000-$30,000 worth of grapes," Vineyard Manager, Hazlitt 1852 Vineyards "I am delighted to tell you that we suffered less overall bird damage with the Bird Gard and Crop Gard combination this year than any year previous. In fact, the systems proved superior to the netting and cannons we used in the past," Woodward Canyon Winery "Usually we loose 25%-33% of the Pinot Noir even with dawn to dusk patrol and 2 propane cannons. This year we lost less than 5 pounds of grapes. We harvested an additional $3450 worth of grapes on15 acres," Foris Vineyards Winery Both the Super PRO and the Mega PRO have the chip in front so they can be easily replaced with new chips. The Mega PRO has 120 decibels of output and covers up to 30 acres. It's 60 times as powerful as the Super PRO ($599) that covers up to 6 ac res. Included with the Mega PRO is a 200 watt amplifier, a 20 speaker tower, and a 40 watt solar panel. Discounted:$2800 Mega PRO JWB Marketing LLC birddamage.com To order call: (800) 555-9634 Bird Gard Super PRO with 4 speakers covers up to 6 aces. $599 Vineyard managers say the Bird Gard PRO Combo can be as effective as netting.