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David Jespersen and Brian Schwartz

influence g S and the closure of stomata, including plant signaling molecules and environmental cues such as abscisic acid, whole-plant hydraulic conductance, vapor pressure deficits, light and CO 2 , ions, and metabolites ( Popova et al., 2000

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Albert H. Markhart III and Barbara Smit

Published as paper 16993 of scientific journal series of the Minnesota Experiment Station on research conducted under Minnesota Experiment Station Project 0302-4821-82. Additional support was provided by the Univ. of Washington Graduate

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Juan C. Díaz-Pérez, Kenneth A. Shackel, and Ellen G. Sutter

Little is known about the physiological changes that occur during acclimatization and how these changes influence plant survival and growth in the new environment. In particular, it is unclear to what extent in vitro-formed roots are functional in water uptake, particularly when the plantlet is exposed to conditions of increasing evaporative demand. Tissue-cultured shoots and plantlets (shoots with roots) were acclimatized by exposing them to a linear reduction in relative humidity (RH) from 99 % to 75%over 4 days. When conductance was measured at 95% RH (21 C), in vitro shoots and plantlets showed a very high initial conductance, followed by a gradual decline, reaching steady state in 12 hours. Acclimatized shoots and plantlets had a 50% lower initial conductance compared to nonacclimatized ones, and reached steady state in 4 hours. The reduction in conductance as a result of acclimatization most likely contributes to a reduced transpiration under conditions of increased evaporative demand. Roots formed in vitro were associated with a higher plant water status, suggesting that these roots were functional in water uptake. Relative water content of the shoot was positively correlated with leaf conductance and net photosynthesis. We suggest that tissue-cultured plantlets behave as hydraulically integrated units, in which there must be a coordination between control of water loss by the shoot and uptake of water by the root to maintain a favorable plant water balance. Our results also indicate that methods that use excised shoots or leaves to determine transpiration gravimetrically may not accurately represent the stomatal water loss characteristics of tissue-cultured plants.

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Jingjing Yin, Nina L. Bassuk, Madeline W. Olberg, and Taryn L. Bauerle

is referred to as “transplant shock,” in which a plant shows less shoot growth, smaller “scorched” new leaves, and a general lack of vigor ( Watson and Himelick, 1983 ). Root hydraulic conductance describes the ability of roots to take up water from a

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Manuel G. Astacio and Marc W. van Iersel

watered, the leaf concentration of ABA rapidly decreases and stomatal conductance ( g S ) returns to its pre-stress state ( Franks and Farquhar, 2001 ). ABA may extend the shelf life of plants by slowing water consumption. Sprenches (spraying and allowing

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L.S. Chang, A.F. Iezzoni, G.C. Adams, and F.W. Ewers

Abbreviations: K h , hydraulic conductance per pressure gradient. 1 Dept. of Horticulture. Current address: National Taiwan Univ., Taipei, Taiwan, R.O.C. 2 Dept. of Horticulture. 3 Dept. of Botany and Plant Pathology. Acknowledgement is made to the

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Toshio Shibuya, Akihito Sugimoto, Yoshiaki Kitaya, Makoto Kiyota, Yuichiro Nagasaka, and Shinya Kawaguchi

The leaf vapor conductance ( g l ) is a useful index for the management of plant water status. The value of g l is often estimated using porometry (e.g., Bakker, 1991 ). Bunce (2006) noted, however, that porometry is not suitable to evaluate

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Nicole L. Waterland, John J. Finer, and Michelle L. Jones

from Green Circle Growers (Oberlin, OH), and Expt. 1 was conducted in Wooster, OH, from 28 Sept. to 9 Oct. 2007. Average greenhouse temperatures were 26/21 ± 2/3 °C day/night with daytime (0700–1800 hr ) average relative humidity of 59.7% ± 7

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Kristen Harper, Curt R. Rom, and Jason McAfee

As funding directed toward research has diminished, it has become vital seek other avenues of support to maintain long term field projects. To meet this need, the University of Arkansas Horticulture Department began the Friends of Fruit (FOF) program during 2004 engaging volunteers in conducting tree fruit field research. Volunteers were graduates of the Master Gardener program and executed tasks including data collection and plot maintenance. Objectives of this study were to evaluate the experiences and benefits to the volunteers and horticulture department, and to assess the success of the FOF program in providing assistance and support to research. All volunteers and facilitators were interviewed. Interview questions were designed to understand the motivation and level of volunteer activity, determine if training and supervision was adequate, and determine if ample recognition occurred. Volunteers sought experience and knowledge with fruit crops. Costs to volunteers included time and travel, conversely benefits included knowledge, experience and fellowship. Volunteers planned to repeat the program and were pleased with the recognition they received. Facilitators noted that volunteers had basic horticultural knowledge and the desire to learn. The program did call for improved task management and increased planning time by facilitators. The program succeeded in benefiting volunteers and horticultural research. The FOF volunteers contributed to fruit research by harvesting ≈4,000 kg of fruit samples and providing >200 hours of time.

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Lesley A. Judd, Brian E. Jackson, William C. Fonteno, and Jean-Christophe Domec

and hydraulic conductance (reciprocal of hydraulic resistance) ( Passioura and Munns, 1984 ; Ramos and Kaufmann, 1979 ; Rieger and Litvin, 1999 ). Hydraulic conductance ( K r ) is a measure of the efficiency of bulk flow through plant shoots or roots