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Brandon M. Miller and William R. Graves

, are considered important for posttransplant establishment and survival ( Schultz and Thompson, 1990 ). Initiation of lateral roots is stimulated by auxin and other growth regulators ( Esau, 1965 ). Plant growth regulators have been used with other

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M. J. Grochowska, A. Karaszewska, B. Jankowska, J. Maksymiuk, and Max W. Williams

Abstract

The levels of auxin, gibberellin, and cytokinin were measured using bioassay methods in pruned and unpruned apple trees (Malus domestica Borkh. cv. McIntosh). Vigorous shoot growth following heavy dormant pruning was accompanied by an increase in cytokinin concentration in the tissues in the early spring. As cell division and cell expansion progressed, the levels of auxin and gibberellin increased. The gibberellin activity in samples from pruned trees was 3 times higher than in samples from unpruned trees. Pruning diminished the midsummer level of cytokinins in the annual shoots.

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John L. Caruso

Abstract

Phytohormones occur in bound and free forms. The bound form is designated by some as conjugated if the hormone is covalently linked to a small molecule and as bound if it is attached to a macromolecule or cell particle (39). However, the terms bound and conjugated will be used interchangeably here, as they are in many other treatises. There is more information published on the relationship between free and conjugated 1H-indole-3-acetic acid (IAA) than is available on similar relationships of other hormones. Free IAA is the active form of the hormone. This activity was seen, for example, when IAA conjugates were applied to the first internode section of bean (Phaseolus vulgaris L.). The promotion of curvature was traceable to the amount of free IAA released from the conjugates (4). Excellent reviews of conjugated auxins are available (3, 9). It is the purpose of this communication to acquaint the reader with some of the broader aspects of conjugated auxin and then to focus on the use of auxin conjugates in tissue culture.

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Michele R. Warmund, David H. Trinklein, Mark R. Ellersieck, and Reid J. Smeda

Auxin herbicides have been registered for postemergence control of broadleaf weeds in agricultural crops for more than 50 years ( Peterson et al., 2016 ). Since their initial development, different formulations of auxin herbicides, such as 2,4-D

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Ying Gao, Hao Liu, and Dong Pei

on morphology is easy, but the relationship between the morphology and physiology of walnut catkins has not been established. Auxin is an essential hormone that has been implicated in many aspects of plant growth and development ( Woodward and Barrel

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Ji-Yu Zhang, Zhong-Ren Guo, Rui Zhang, Yong-Rong Li, Lin Cao, You-Wang Liang, and Li-Bin Huang

with varying concentrations of selected auxins and different combinations of media and air temperatures. Materials and methods Plant materials. Pecan seeds were harvested at maturity in Oct. 2012 and planted in Feb. 2013 in a greenhouse at the Nanjing

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Eugene K. Blythe and Jeff L. Sibley

is preferred as cutting material ( Berry, 1994 ). Auxin treatment has traditionally been recommended and used in commercial propagation for rooting cuttings. Knight et al. (1993) rooted stem cuttings of ‘Dwarf Burford’ holly prepared from dormant

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V. Tuli

3-Methyleneoxindole (MO), a metabolite of the plant auxin 1- H-indole-3-acetic acid (IAA), is a potent sulfhydryl reagent that can profoundly affect bacterial growth and metabolism. For investigative purposes, MO is obtained from the degradation of 3-bromooxindole-3-acetic acid (3-Br-lAA) in aqueous media. Alternatively, it can be prepared from the riboflavin-catalyzed photooxidation of IAA. My earlier claims that MO possesses auxin activity were refuted by independent investigators either because the results could not be reproduced when 3-Br-IAA was used, or the results were ascribed to contamination with residual IAA if MO obtained from photooxidation was used. Recent investigations indicate that, contrary to previous assumptions, the quantitative degradation of 3-Br-lAA resulting in the formation of MO is not instantaneous; depending on the purity of 3-Br-lAA, it may take several hours to several days to reach completion. Furthermore, aqueous solutions of MO ≥0.1 mm are rapidly polymerized, thus causing a loss of biological activity. These findings may explain why MO that is derived from 3-Br-lAA often fails to produce auxin action. Ultrapure MO, obtained from either 3-Br-IAA or photooxidation, is 50- to 1000-fold as effective as IAA in the straight growth assay, induction of xylogenesis in parenchymatous tissue, and rooting of explants in tissue culture.

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Eugene K. Blythe

requirement of an auxin treatment to promote rooting of the cuttings has not been noted. Comparing rooting of softwood and hardwood cuttings of confederate rose during the winter, spring, and monsoon seasons in India, Pandey and Vaish (1990) determined that

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Jenny B. Ryals, Patricia R. Knight, and Eric T. Stafne

was to evaluate the effect of auxin sources on rooting for seven species of passion fruit. Materials and methods The seven passion fruit species chosen were banana passion fruit, blue passionflower, two maypops (one from Mississippi and one from