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Jenna Sicuranza and Nathaniel A. Mitkowski

regulator treatments were prepared by adding IAA and 2iP to this basal media. Medium I contained 1 mg·L −1 (5.7 μ m ) IAA and 5 mg·L −1 (24.5 μ m ) 2iP; medium II contained 4 mg·L-1 (22.8 μ m ) IAA and 15 mg·L −1 (73.8 μ m ) 2iP ( Meyer, 1982 ). One

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Maria A. Macias-Leon and Daniel I. Leskovar

temperatures, resulting in better crop stand and higher yields ( Halmer, 2004 ). Auxin is known to be involved in germination and root development processes. During seed imbibition, the free natural auxin, IAA, accumulates before the initiation of root

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Ursula K. Schuch, Anita N. Miller, and Leslie H. Fuchigami

Dormant coffee (Coffea arabica L.) flower buds require water stress to stimulate regrowth. A xylem specific watersoluble dye, azosulfamide, was used to quantify the uptake of water by buds after their release from dormancy by withholding water. In non-stressed flower buds, the rate of water uptake was generally slower and variable. In stressed flower buds, the rate of uptake tripled from one day to 3 days after rewatering and preceded the doubling of fresh and dry weight of buds. Free, ester, and amide IAA levels of developing flower buds were measured by GCMS-SIM using an isotope dilution technique with [13C6] IAA as an internal standard. Throughout development, the majority of IAA was present in a conjugated form and the dominant form was amide IAA. The proportions of amide and free IAA changed rapidly after plants were water stressed until day 3, and preceded the doubling of fresh and dry weight. Correlation coefficients of 0.9, 0.7, and 0.7 (p<0.l) were found between auxin content and fresh weight, dry weight, and rate of water uptake, respectively.

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Scott J. Nissen and Ellen G. Sutter

The relative stabilities of IAA and IBA under various tissue culture procedures were determined. IBA was significantly more stable than IAA to autoclaving. IBA was also found to be more stable than IAA in liquid Murashige and Skoog medium (MS) under growth chamber conditions. The stabilities of IBA and IAA were similar in agar-solidified MS. Light provided by cool-white fluorescent bulbs promoted degradation of IAA and IBA in both liquid and agar media. Activated charcoal in concentrations as high as 5% was found to adsorb more than 97% of IAA and IBA in liquid MS. These results have important implications for the preparation, storage, and handling of IBA and IAA in plant tissue culture. Chemical names used: indole-3-acetic acid (IAA); indole-3-butyric acid (IBA).

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Isa Bertline and Carol J. Lovatt

Tryptophan is known to be a precursor of IAA in plants. The amount of IAA available for the development of avocado fruit might be a limiting factor for its growth. It is well known that IAA is not transported into developing fruit along its strictly basipetal transport route. Therefore, IAA present in fruit must be synthesized in situ. We investigated the possibility that tryptophan or its metabolites are transported from leaf to fruit.

An HPLC method was developed to quantitatively isolate and measure tryptophan and all well known intermediates in the synthesis of IAA. Avocado leaves were fed L-[side chain-3-14C] tryptophan and its transport and metabolism to IAA within the leaf and within the fruit were monitored over time. Significant movement of tryptophan or a metabolite from leaf to fruit occurs in 24 h.

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Yasuyoshi Hayata, Xin-Xian Li, and Yutaka Osajima

An investigation was conducted to determine how pollination and CPPU treatment influence endogenous IAA and ABA content in netted muskmelon [Cucumis melo L. (Reticulatus Group) `Crest Earl's'], and to clarify their roles in fruit set and development in relation to these endogenous plant hormones. CPPU treatment at anthesis significantly increased the fresh weight of ovaries, whether the flowers were pollinated or not, but from 6 days after anthesis (DAA) the growth rate in the nonpollinated + CPPU treatment tended to be lower than the growth rates in the pollination treatment plots. Ovaries of nonpollinated flowers not treated with CPPU failed to grow and turned brown within 4 DAA. IAA content in the placenta of fruit from pollinated flowers increased rapidly from the day of anthesis to 2 DAA and remained at relatively high levels. IAA content in the placenta of parthenocarpic fruit induced to develop by CPPU treatment was lower than that of fruit from pollinated flowers but the pattern was almost the same as that in fruit of pollinated flowers. Conversely, IAA content in the placenta of fruit from nonpollinated flowers not treated with CPPU decreased sharply after anthesis. IAA content in the mesocarp of CPPU-treated fruit, whether or not the flowers were pollinated, increased significantly from the day of anthesis to 2 DAA, then decreased to almost the same level as that of the pollination-only treatment by 10 DAA, while the IAA content of nonpollinated CPPU-treated fruit declined even further. IAA content in the mesocarp of fruit from nonpollinated flowers not treated with CPPU decreased sharply. ABA contents in both the placenta and mesocarp of muskmelon that would set decreased after anthesis while the ABA content of muskmelon that would not set increased rapidly. Results suggest that pollination and CPPU treatment increased endogenous IAA content and decreased endogenous ABA content to promote the set and growth of fruit during early development. Chemical names used: [1-(2-chloro-4-pyridyl)-3-phenylurea] (CPPU); indole-3-acetic acid (IAA); abscisic acid (ABA).

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Shiow Y. Wang, Miklos Faust, and Michael J. Line

The effect of IAA on apical dominance in apple buds was examined in relation to changes in proton density (free water) and membrane lipid composition in lateral buds. Decapitation induced budbreak and enhanced lateral bud growth. IAA replaced apical control of lateral buds and maintained paradormancy. Maximal inhibition was obtained when IAA was applied immediately after the apical bud was removed; delaying application reduced the effect of IAA. An increase in proton density in lateral buds was observed 2 days after decapitation, whereas the change in membrane lipid composition occurred 4 days later. Removing the terminal bud increased membrane galacto- and phospholipids and the ratio of unsaturated to corresponding saturated fatty acids. Decapitation also decreased the ratio of free sterols to phospholipids in lateral buds. Applying thidiazuron to lateral buds of decapitated shoots enhanced these effects, whereas applying IAA to the terminal end of decapitated shoots inhibited the increase of proton density and prevented changes in membrane lipid composition in lateral buds. These results suggest that change in water movement alters membrane lipid composition and then induces lateral bud growth. IAA, presumably produced by the terminal bud, restricts the movement of water to lateral buds and inhibits their growth in apple.

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Mateja Štefančič, Franci Štampar, and Gregor Osterc

The influence of two exogenously applied auxins (IAA and IBA) on the root and shoot development of leafy cuttings was analyzed at 'GiSelA 5', the dwarfing cherry rootstock. IBA (indole-3-butyric acid) hindered the callus formation in the early period of root development and it was more successful than IAA (indole-3-acetic acid) in promoting earlier root development. IBA also influenced the stronger shoot growth and the development of acrobasal type of the rooting system, and induced higher number of roots. Those parameters are very important for the quality and survival of the new plants and they are not the consequence of the higher IAA content in the rooting zones of cuttings in the first days of root development. Both auxin treatments had no effect on the final percent of the rooted cuttings neither on the survival of cuttings, but they increased the percent of rooted cuttings without callus. The root system with callus proved less qualitative, because the cuttings with such root system developed significantly less roots per rooted cutting and their shoot length was shorter than those of the cuttings without callus at both auxin treatments. Exogenously applied auxins were not crucial for root formation, however their application resulted in higher percent of more qualitative 'GiSelA 5' leafy cuttings. IBA proved as the most efficient treatment and it additionally induced earlier root formation.

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Wen-Shaw Chen

The changes in cytokinins and gibberellins in xylem sap of lychee (Litchi chinensis Sonn. cv. Heh yeh) trees were investigated at the stages of leaf expansion, dormant bud (when apical leaves are dropped), 30 days before flower bud formation, flower bud formation, and full bloom of grafted field-grown lychee trees. Also; the diffusible IAA and ABA in diffusate from shoot tips were examined at the successive stages of development. High gibberellin was found in the xylem sap at the stage of leaf expansion. A constant level of IAA was maintained through the five growth stages. At 30 days before flower bud formation, ABA increased dramatically. Concurrently, total cytokinin content increased in the xylem sap, reaching a maximum during flower bud formation and full bloom. Gibberellin content in the xylem sap was at a low level 30 days before flower bud formation and through the stage of flower bud formation.

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Mark A. Ritenour, Ellen G. Sutter, David M. Williams, and Mikal E. Saltveit

This study was undertaken to determine if endogenous IAA content and axillary bud development correlate with phenylalanine ammonia-lyase (PAL) induction and russet spotting (RS) susceptibility among RS susceptible and resistant cultivars of Iceberg lettuce (Lactuca sativa L.). Final levels of ethylene-induced PAL activity and RS development were highly correlated among cultivars, field conditions, and harvest dates. Harvested Iceberg lettuce midribs contained relatively low amounts of free IAA (maximum of 5.2 ng·g-1 fresh weight). There was poor correlation between free IAA content in lettuce leaf midribs and final RS development among all cultivars, growing conditions, and harvest dates. Axillary bud development, as measured by the number of visible buds per head, bud weight, or bud length, were not significantly correlated with final RS development or midrib IAA content. Cultivars with higher initial free IAA content lost much of their IAA after 8 days storage at 5C in air ± ethylene.