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Jesse R. Quarrels and Paul G. Thompson

An experiment was conducted to determine the rate and frequency of irrigation needed for optimum yield in sweetpotato (Ipomoea batatas (L.)Lam). A line source irrigation system was used to provide continuously increasing amounts of water at each irrigation. The physiological responses of sweetpotato to water application were measured. There was an increase in leaf water potential with increasing rates of irrigation. Leaf diffusive resistance decreased as total water rate increased to 76% of pan evaporation (Epan) and then increased with higher rates of irrigation. Marketable yields increased as total water rate increased to 76% of Epan and then decreased rapidly with higher irrigation rates. Water relations measurements indicated that reduction in yield with higher amounts of water application was due to low soil oxygen content.

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Vahid Rahimi Eichi, Stephen D. Tyerman and Michelle G. Wirthensohn

the assumption that under non-stress conditions, genotypic variation affects water relations and WUE i in almond plants. We further assessed the hypothesis that genotypic variation in almond may lead to anatomical differences in mesophyll, which may

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J. Ryan Stewart, Roger Kjelgren, Paul G. Johnson and Michael R. Kuhns

Although transplanted trees typically establish and grow without incident in frequently irrigated turfgrass, their performance in precisely irrigated turfgrass in an arid climate is not known. We investigated the effect of precision irrigation scheduling on growth and water relations of balled-and-burlapped littleleaf linden (Tilia cordata Mill. `Greenspire') planted in buffalograss (Buchloë dactyloides [Nutt.] Engelm. `Tatanka') and kentucky bluegrass (Poa pratensis L.). Over 2 years, trees in turfgrass were irrigated either by frequent replacement based on local reference evapotranspiration, or precision irrigated by estimating depletion of soil water to the point of incipient water stress for each turfgrass species. Predawn leaf water potential and stomatal conductance of trees were measured during first-year establishment, and predawn leaf water potential was measured during a mid-season water-deficit period during the second year. Trunk diameter growth and total tree leaf area were measured at the end of each year. Values of predawn leaf water potential and stomatal conductance of trees in precision-irrigated buffalograss were lower (–0.65 MPa, 25.3 mmol·m–2·s–1) than those of trees in the other treatments near the end of the first growing season. The longer interval between precision irrigations resulted in mild water stress, but was not manifested in growth differences among trees across treatments during the first season. During the water-deficit period of the second year, there was no evidence of stress among the trees regardless of treatment. At the end of the second season, total leaf area of trees grown in precision-irrigated kentucky bluegrass (1.10 ± 0.34 m2) was 46% of that of trees grown in buffalograss (2.39 ± 0.82 m2) that were irrigated frequently. Trunk diameter growth of trees in frequently irrigated kentucky bluegrass (1.91 ± 2.65 mm) was 29% of that of the trees grown in buffalograss (6.68 ± 1.68 mm), regardless of irrigation treatment, suggesting a competition effect from kentucky bluegrass. We conclude that frequent irrigation of balled-and-burlapped trees in turfgrass, particularly buffalograss, is more conducive to tree health during establishment than is maximizing the interval between turfgrass irrigation. Regardless of irrigation schedule, kentucky bluegrass appears to impact tree growth severely during establishment in an arid climate.

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Aidan D. Farrell, Sarah Evelyn, Adrian M. Lennon and Pathmanathan Umaharan

vase life and the water relations of the cut flower ( Elibox and Umaharan, 2010 ; Mujaffar and Sankat, 2003 ; Paull et al., 1985 ). Similar associations have been found in other species and can result from either an obstruction in water transport or a

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Smita Barkataky, Robert C. Ebel, Kelly T. Morgan and Keri Dansereau

were conducted without adequate knowledge of soil moisture content or were conducted in dry soils that imposed drought stress. Thus, it is not known how cold acclimation changes water relations of citrus independent of soil moisture content. Citrus cold

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Nauja Lisa Jensen, Christian R. Jensen, Fulai Liu and Karen K. Petersen

potentials ( Liu et al., 2007 ). To optimize irrigation strategies for strawberries, it is important to know how different irrigation strategies influence physiological reactions (i.e., plant–water relations), stomatal conductance ( g s ), and chemical

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Stephen A. Prior, G. Brett Runion, S. Christopher Marble, Hugo H. Rogers, Charles H. Gilliam and H. Allen Torbert

). Nonetheless, the increased biomass production under high CO 2 should be advantageous for horticultural plants in that they should attain a marketable size more rapidly. PLANT WATER RELATIONS In addition to the effects of CO 2 on photosynthesis and C

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Michael J. Costello

, how one species, nodding needlegrass, affects soil– and vine–water relations. Vine vigor and yield data of nodding needlegrass and other cover crops in this study are presented in another paper ( Costello, 2010 ). The native range of nodding

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Youssef Rouphael, Mariateresa Cardarelli, Giuseppe Colla and Elvira Rea

full and deficit irrigation regimes. Grafted and ungrafted plants were compared in terms of yield, plant growth, fruit quality parameters, leaf gas exchange, water relations, macroelement content in fruits and leaves, and water use efficiency

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A. Naor, Y. Gal and B. Bravdo

The effect of shoot density and crop level on gas exchange and water relations of filed-grown Sauvignon blanc was studied. Ten and 44 shoots/vine and one and two clusters per shoot treatments were examined in a factorial design. The two-cluster treatments had higher stem water potential (Ystem), assimilation rate, and stomatal (gs) and nonstomatal (gm) conductance. A quantitative analysis suggests that capacitance cannot account for the simultaneous increase in gs and Ystem in the two clusters treatment. The two-cluster treatment had higher Ystem for similar transpiration rates (similar gs) compared to the one-cluster treatment. The similar transpiration rate and lower stem to root water potential difference in the two-cluster treatment was explained by increased root permeability in the two-cluster treatment. The similar gs–gm, in spite of a meaningful decrease of gs with decreasing Ystem, suggests that gs and gm synchronize themselves to perturbations of gm due to sink effect and gs due to water stress.