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William H. Rein, Robert D. Wright, and John R. Seiler

Abbreviations: ψ, water potential; RCB, randomized complete block. 1 Former Graduate Student, Dept. of Horticulture. 2 Professor, Dept. of Horticulture. 3 Assistant Professor, Dept. of Forestry. The cost of publishing this paper was defrayed in part

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Amos Naor

Interrelations between water potential and fruit size, crop load, and stomatal conductance were studied in drip-irrigated `Spadona' pear (Pyrus communis L) grafted on quince C (Cydonia oblonga L.) rootstock and growing in a semi-arid zone. Five irrigation rates were applied in the main fruit growth phase: rates of 0.25, 0.40, 0.60, 0.80, and 1.00 of “Class A” pan evaporation rate. The crop in each irrigation treatment was adjusted to four levels (200 to 1200 fruit per tree) by hand thinning at the beginning of June 1999. The crop was harvested on 1 Aug. 1999, and fruit size was determined by means of a commercial sorting machine. Soil, stem, and leaf water potentials and stomatal conductance were measured during the season. Crop yield was highly correlated with stem and soil water potentials. The highest midday stem water potential was lower than values commonly reported for nonstressed trees, and was accompanied by high soil water potential, indicating that the maximal water absorption rate of the root system under those particular soil conditions was limited. Stomatal conductance was highly correlated with leaf water potential (r 2 = 0.54), but a much better correlation was found with stem water potential (r 2 = 0.80). Stomatal conductance decreased at stem water potentials less than -2.1 MPa. Both stem water potential and stomatal conductance were unaffected by crop load under a wide range of irrigation rates.

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

inhibition of photosynthesis; WUE, water-use efficiency; ψ L , leaf water potential. 1 Former Graduate Student. Present address: Dept. of Horticulture, Auburn Univ., AL 36849. 2 Professor. 3 Assistant Professor, Dept. of Forestry. Technical guidance and

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Soo-Hyung Kim, Kenneth A. Shackel, and J. Heinrich Lieth

We thank Alexandra Rosati and Jonathan Guan from the NSF Young Scholars Program for carrying out stem water potential measurements and preliminary photosynthesis measurements, respectively. We thank Drs. Loren Oki and Mark Roh for helpful comments

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Mengmeng Gu, Curt R. Rom, James A. Robbins, and Derrick M. Oosterhuis

generally reduces stomatal conductance ( g S ), net photosynthesis (Pn), leaf water potential, and growth rate ( Cregg, 1994 ; Matthews and Boyer, 1984 ; Pääkkönen et al., 1998a ). Plants adapt to water-deficit stress by increasing water uptake and

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Jane M. Petitte and Douglas P. Ormrod

Abbreviations: CSTR, continuously stirred tank reactor; PLA, planar leaf area; π osmotic potential; ψ leaf , leaf water potential. 1 Current address: 620 Shadywood Lane, Raleigh, NC 27603. This paper is a portion of a thesis submitted by J.M.P. in

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Bruno Casamali, Marc W. van Iersel, and Dario J. Chavez

expansion stage; Connors, 1919 ). Control trees had trunk diameter and stem water potential greater than the RDI treatments. Similar effects on fruit yield and weight were found by Marsal et al. (2016) in Spain. In Spain, Girona et al. (2005) reported

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Eckhard Grimm and Moritz Knoche

The water potential (Ψ) of the sweet cherry fruit and its two components, osmotic potential (Ψ Π ) and turgor (Ψ P ) (where Ψ = Ψ Π + Ψ P ), are likely to be important factors affecting fruit cracking. First, fruit Ψ affects the rate of water

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Kuo-Tan Li, Jacqueline K. Burns, and James P. Syvertsen

middle section of the canopy. Leaf and fruit retention was measured in all ‘Hamlin’ orange field trials. Leaf water content, leaf dry weight, midday leaf water potential, and leaf chlorophyll fluorescence and chlorophyll content were measured as described

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Xiaoya Cai, Terri Starman, Genhua Niu, and Charles Hall

constant SMCs (9%, 15%, 22%, and 32%), Nemali and van Iersel (2008) found that gas exchange, chlorophyll fluorescence, and leaf water potential were similar between 32% and 22% SMC for impatiens ( Impatiens wallerana Hook.) and salvia ( Salvia splendens