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Christian M. Baldwin, A. Douglas Brede, and Jami J. Mayer

( Baldwin et al., 2012 ; Dant et al., 2005 ; Flessner et al., 2014 ; Hart et al., 2005 ) with little published data regarding possible benefits of glyphosate applications, in particular, growth regulation. Although glyphosate is considered a class D PGR

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Suxiao Hao, Yanfen Lu, Jing Liu, Yufen Bu, Qi Chen, Nan Ma, Zhiqin Zhou, and Yuncong Yao

, the regulation function of GID1 in the determination of the plant growth traits of dwarfing rootstocks is still unclear. Plant growth is also controlled by the regulation of different hormone signals, including auxin, brassinolide, and abscisic acid

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Jack D. Early Jr. and George C. Martin

33 ORAL SESSION (Abstr. 391-397) FRUIT CROPS: GROWTH AND DEVELOPMENT I

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Susan L. Steinberg, Jayne M. Zajicek, and Marshall J. McFarland

43 ORAL SESSION (Abstr. 438-444) WOODY PLANT GROWTH REGULATION

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Robert E. Shar

Plant water deficits usually result in severe inhibition of shoot growth, while root growth is less inhibited or even promoted. Recent advances in understanding the physiology of the differential responses of root and shoot growth to low water potentials will be reviewed.

While it might be readily accepted that hormones arc important in transducing environmental conditions into growth responses, there is surprisingly little definitive evidence for the role of any hormone in regulating plant growth in soils of low water potential. Using maize seedlings as a model system, the increase in ABA that accompanies plant water deficits has been shown to be required for root growth maintenance, and also to play a role in shoot growth inhibition. The action of ABA in root growth maintenance appears to involve regulation of ethylene synthesis and/or sensitivity, while the mechanism of shoot growth inhibition is not known. Evidence that ABA acts as a root `signal controlling shoot growth in drying soil will also be considered.

The importance of osmotic adjustment as a mechanism of growth maintenance at low water potentials has been questioned by suggestions that solute accumulation may be merely a consequence of stress-induced growth inhibition. Recent studies will be discussed which do not support this idea, and suggest that the response may be useful for crop improvement.

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D.M. Pharr, R.T.N. Prata, J.B. Jennings, J.D. Williamson, E. Zamski, Y. Tamamoto, and M.A. Conkling

Increasing salinity of agricultural soils may ultimately limit the sustainability of food production in some areas of the world. Work from our laboratory and the labs of others demonstrates that mannitol, a six-carbon sugar alcohol, is important as a stress-related metabolite in some plants. Mannitol helps plants resist the damaging effects of stressful growth environments, such as drought, high soil salinity, and perhaps attack by microorganisms that cause plant diseases. In the long run, we hope to genetically engineer plants to produce and use mannitol for increased productivity and tolerance to environmental stresses. Basic information about how plants regulate those genes important to mannitol metabolism is of critical importance to this long-term goal. Our laboratory discovered an enzyme, mannitol dehydrogenase, that is the first critical biochemical step in mannitol use in vascular plants. Later, we cloned the gene for this enzyme. We discovered that hexose sugars “turn off” the expression of this gene. So, as long as adequate sugars are available for energy, maintenance, and growth, the production of the mannitolusing enzyme is repressed. After the sugars are gone, mannitol dehydrogenase is produced very rapidly, and this allows mannitol to be used metabolically. This type of gene regulation is ideally designed to help plants cells conserve mannitol as long as possible, which in turn allows the cells to retain stress tolerance as long as possible.

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J. Michael Goatley Jr., Victor L. Maddox, and Robert M. Watkins

. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.

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Chung-Liang Chang and Ming-Fong Sie

influence plant growth height and growth time, even without considering the generic characteristics of the plant itself. To simplify analysis and facilitate the design of the growth regulation system, this study divided the plant growth process into stages

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Peter Alem, Paul A. Thomas, and Marc W. van Iersel

use of PGRs has restrictions in some countries ( Moe et al., 1992a ). Also, if applied in excess, PGRs negatively affect plant quality and growth through phytotoxicity ( Gibson et al., 2003 ) and stunting ( Hamid and Williams, 1997 ). Several

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Nihal C. Rajapakse and John W. Kelly

was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.