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Bruce W. Wood, Charles C. Reilly, and Andrew P. Nyczepir

Mouse-ear (ME) is a severe growth disorder affecting pecan [Carya illinoinensis (Wangenh.) K. Koch] trees from southeastern U.S. Gulf Coast Coastal Plain orchards. Slight to moderate ME was substantially corrected by foliar sprays of either Cu or GA3 shortly after budbreak, but sprays were ineffective for severely mouse-eared trees. Applications of Cu, S, and P to the soil surface of moderately affected trees corrected deficiencies after three years. Incorporation of Cu or P in backfill soils of newly planted trees prevented ME, whereas incorporation of Zn or Ca induced ME and Mn was benign. The severe form of ME, commonly exhibited by young trees, appears to be linked to a physiological deficiency of Cu and/or Ni at the time of budbreak. It likely occurs as a replant problem in second-generation orchards due to accumulation of soil Zn from decades of foliar Zn applications to correct Zn deficiency.

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Tripti Vashisth, D. Scott NeSmith, and Anish Malladi

lycopersicum ) and arabidopsis ( Arabidopsis thaliana ) ( Mao et al., 2000 ; McKim et al., 2008 ). Establishment of the AZ is followed by a phase wherein competence for abscission is attained through developmental and phytohormone signaling ( Taylor and

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Norman B. Best, Xingang Wang, Scottie Brittsan, Eric Dean, Seth J. Helfers, Ryan Homburg, Mariah L. Mobley, Tiffeny L. Spindler, Bofan Xie, Menglu Zhang, Paul M. Hasegawa, Robert J. Joly, David Rhodes, and Brian P. Dilkes

phytohormones and determinants of plant height ( Hooley, 1994 ). Mutants altered in GA biosynthesis or signaling can exhibit a dwarf phenotype ( Helliwell et al., 1998 ; Peng et al., 1997 ). GA has been shown to control multiple aspects of sunflower growth and

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Guo-qing Song, Aaron E. Walworth, and Wayne H. Loescher

amphipolyploid. Movement of Phytohormones Phytohormones play essential roles in plant growth and development. Many phytohormones (e.g., auxin, cytokinin, gibberellin, abscisic acid, jasmonic acid, and salicylic acid) are phloem-mobile signals, able to move from

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Mason T. MacDonald, Rajasekaran R. Lada, Jeff Hoyle, and A. Robin Robinson

possible signal is abscisic acid (ABA). ABA is a natural phytohormone that is known to regulate various plant growth and developmental processes associated with biotic and abiotic stresses, including drought. Endogenous levels of ABA increase in parallel to

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Bo Meyering, Adam Hoeffner, and Ute Albrecht

plant internal conditions ( Simpson and Dean, 2002 ). Bioactive gibberellins (GA) are a class of endogenous phytohormones that positively direct seed germination, stem elongation, and floral initiation and significantly interact with the auxin

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Ju Ding, Kai Shi, Yan-Hong Zhou, and Jing-Quan Yu

phytohormones that are structurally similar to animal and insect steroid hormones. They control a broad range of processes, including seed germination, stem elongation, cell division and expansion, xylem differentiation, plant growth, and apical dominance

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Jingyi Lv, Yonghong Ge, Canying Li, Mengyuan Zhang, and Jianrong Li

., 2007 ). Recent discoveries showed that JAZ transcriptional repressors are key regulators of JA signaling and that they function as crucial interfaces to mediate the synergy and antagonism between JA and other phytohormones, such as ethylene and

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A. Smigocki and F. Hammerschlag

Immature `Redhaven' peach (Prunus persica L. Batsch) embryos were infected with Agrobacterium tumefaciens strain tms328::Tn5 carrying the functional cytokinin gene. Shoots were regenerated from callus grown on MS medium without added phytohormones and subsequently rooted on half-strength MS medium with 2.8 -naphthaleneacetic acid. These plants exhibited an increased frequency of branching in vitro. Low levels of cytokinin gene transcripts were detected in these cells by Northern analysis, and using an ELISA assay, the cytokinins zeatin and zeatinriboside were determined to be on the average 30-fold higher. From these results, the expression of the cytokinin gene appears to promote growth of cells in the absence of phytohormones thus serving as a marker for transformation and a promoter of morphogenesis without a 2,4-dichlorophenoxyacetic acid inductive step.

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Henry E. DeVries II, Joseph P. Lardner, and Kenneth W. Mudge

To test the hypothesis that phytohormone production is related to mycorrhizae formation 29 isolates of ectomycorrhizal fungi have been evaluated for production of ethylene and auxin in pure culture and for their ability to form ectomycorrhizae with Pinus mugo. The fungi tested included a series of monokaryotic isolates of Laccaria bicolor and dikaryotic isolates of Amanita muscaria, Hebeloma crustuliniforme, L. laccata, L. proxima, Pisolithus tinctorius, Rhizopogon ellenae, and R. vinicolor. Inoculated root systems were rated for mycorrhizae formation, root/shoot ratio and root morphology. P. tinctorius isolates which formed abundant mycorrhizae produce no ethylene in vitro, but did produce the auxin IAA. L. bicolor isolates produced ethylene as well as auxins putatively identified as IAA, and IBA. Correlations between phytohormone production and mycorrhizogenicity will be presented.