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D. Joseph Eakes, Robert D. Wright, and John R. Seiler

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Alexander Lang and Richard K. Volz

The effects of spur leaf removal on xylem sap flows and calcium accumulation in fruit of apple (Malus ×domestica Borkh. `Royal Gala') were determined 56 to 61 days after full bloom. Fruit calcium concentrations were reduced but fruit size was not influenced by partial spur defoliation at bloom. Apples exchanged xylem sap with the tree in daily cycles of flow reversal. The presence of local spur leaves promoted this exchange by accentuating the xylem sap drawn out of the fruit during the day, requiring more to flow back into the fruit at night to replace it. Calcium concentrations were lower in the xylem sap leaving the fruit than in that entering it. The reduced calcium accumulation in the fruit borne on defoliated spurs can therefore be attributed to the reduced volume of xylem sap exchanged between tree and fruit.

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Ken Shackel

–plant–atmosphere continuum model ( Fig. 1 ), which forms the basis for our current understanding of plant–water relationships and the responses of plants to water-limited conditions, suggests that plant-based measures such as plant water potential should be the most

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Steven H. Goertz and Janice M. Coons

Seeds of two tepary bean lines (Phaseolus acutifolius Gray var. latifolius) and one navy bean cultivar (P. vulgaris L. `Fleetwood') were tested with 0.0-, – 0.3-, –0.6-, -0.9-, -1.2-, or – 1.5-MPa NaCl solutions to determine their relative salt tolerance during germination and emergence. Developmental stage was not affected at – 0.3 MPa, but with salinities more negative than -0.9 MPa, `Fleetwood' developed more slowly than the tepary lines; no plants emerged at – 1.5 MPa. Teparies tended to maintain higher water and osmotic potentials than navy over the range of NaCl concentrations used, although turgor was similar for all three genotypes. Leaf area was reduced more in navy than in white tepary at – 0.6 and – 0.9 MPa. Dry weights of navy were higher than those of either tepary bean at all NaCl concentrations, although decreases at higher salinities relative to 0.0 MPa were greater for navy than for teparies. Root: shoot ratios were higher at – 0.3 MPa than at 0.0 MPa, but were lower at the higher NaCl concentrations for all three genotypes. Overall, tepary beans tolerated NaCl better than navy. The characteristic that best indicated differences in salt tolerance was developmental stage.

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Roger Kjelgren, Lixue Wang, and Daryl Joyce

water-requiring landscapes. Anisohydric species tolerate greater soil water depletion by maintaining open stomata and generating more negative internal water potential while scavenging soil water under water stress, particularly if deep-rooted ( West et

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Brian Makeredza, Michael Schmeisser, Elmi Lötze, and Willem J. Steyn

saturated vapor pressure of the air at the relative humidity of the air in the hour that the maximum air temperature was attained. Measurements of stem water potential, soil water content, and sunburn were taken on Days 0, 8, and 15 (14, 22, and 29 Mar

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Rémy E. Milad and Kenneth A. Shackel

Abbreviations: DFB, days after full bloom; Ψ, water potential; Ψ P , turgor potential; Ψ S , osmotic potential. 1 Graduate Student/Research Assistant. The cost of publishing this paper was defrayed in part by the payment of page charges. Under

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L.E. Hinesley and L.K. Snelling

Abbreviations: MC, moisture content; ψ, needle water potential; VPD, vapor pressure deficit. 1 Associate Professor. 2 Agricultural Research Technician. This research was funded by the North Carolina Agricultural Research Service, Raleigh, NC

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Ursula K. Schuch, Leslie H. Fuchigami, and Mike A. Nagao

Abbreviation: WP, water potential. 1 Current address: Dept. of Botany and Plant Sciences, Univ. of California, Riverside, CA 92521-0214. Oregon” Agricultural Experiment Station Technical paper no. 9611. This research was supported in part by the U

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Mark Rieger

Abbreviations: A, net CO 2 assimilation; g, stomatal conductance; L p , root hydraulic conductivity; NUE, nitrogen-use efficiency; RH, `Redhaven'; WUE, water-use efficiency; Ψ water potential. A contribution of the Georgia Agricultural Experiment