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Gary L. McDaniel, Effin T. Graham, and Kathleen R. Maleug

The effects of growth-retarding chemicals on stem anatomy were compared on poinsettia (Euphorbia pulcherrima Wind. `Annette Hegg Dark Red'). Micrographic examinations revealed that secondary walls of nonsclerotic phloem fiber cells were either completely or greatly reduced by retardant treatment. Wall thickening of phloem fiber cells was eliminated by paclobutrazol foliar sprays at 25 mg·liter-1. Fiber cell development was reduced, but not eliminated, by sprays of chlormequat and ancymidol at standard rates, while the triazole uniconazole at 10 mg·liter-1 permitted only limited fiber wall thickening. Chemical names used: (2-chloroethyl)-trimethyl ammonium chloride (chlormequat); α -cyclopropylα- (4-methoxyphenyl) -5-pyrimidine methanol (ancymidol); (E)-(p -chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl-1-penten-3-ol (uniconazole): and (R*,R*)- β -[(4-chlorophenyl)methyl]- α -(1,1-dimethylethyl)- 1 H-1,2,4,triazole-1-ethanol (paclobutrazol).

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J. Naalamle Amissah, Dominick J. Paolillo Jr, and Nina Bassuk

), the parenchymatous gaps. The stem anatomies of Q. macrocarpa and Q. bicolor were qualitatively similar with regard to cell types and tissue organization. No detectable anatomical changes were observed the first 6 d after IBA application. Eight

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Michele R. Warmund, Billy G. Cumbie, and Mark V. Coggeshall

of chestnut has been problematic with commonly used nursery methods, experiments were conducted to: 1) examine the stem anatomy of Chinese chestnut rootstocks; 2) determine if the presence of secondary phloem fibers in the stem tissue is associated

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Huan-Keng Lin, Tzu-Yao Wei, Chin-Mu Chen, and Der-Ming Yeh

on stem anatomy or MOE of trailing cultivars. Genetic control of growth habit varies among plant species. For example, growth habit of cowpea [ Vigna unguiculata (L.) Walp.] is governed by two allelic pairs, AA and BB . The genotype A _ B _ has

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Cheryl L. Moore* and Tracy A.O. Dougher

Bur oak, Quercus macrocarpa Michaux, does not root readily from cuttings, and is considered a recalcitrant species. A method producing industry-acceptable levels of rooted cuttings has not been determined. In this study, we explored the possibility of a physical barrier to root initiation. Bur oak stems exhibit a pentarch vascular cylinder, with roots and leaf traces only initiating at the five “points” of the vascular system. External to this vascular system is a series of sclerified tissue, both fibers and sclerenchyma. Both light microscopy and electron microscopy were utilized to determine whether a combination hedging and etiolation treatment of parent plants would inhibit formation of sclerified tissues.

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Mack Thetford, Stuart L. Warren', Frank A. Blazich, and Judith F. Thomas

Uniconazole was applied as a foliar spray at 0, 90, 130, 170, or 210 ppm to rooted stem cuttings of `Spectabilis' forsythia (Forsythia xintermedia Zab.) potted in calcined clay. Uniconazole resulted in higher total leaf chlorophyll (chlorophyll + chlorophyll,) concentration and a decreased ratio of chlorophyll a: b. Stomata1 density of the most recently matured leaves increased linearly with increasing uniconazole concentration 40, 60, and 100 days after treatment (DAT). The number of stomata per leaf (stomata1 index) increased linearly with increasing concentration of uniconazole throughout the initial 100 DAT. Uniconazole suppressed stomata1 length at all sampling dates and the level of suppression increased with increasing concentration of uniconazole from 20 to 100 DAT. Stomata1 width was suppressed by uniconazole at 40 DAT. Leaves developed after uniconazole application had higher levels of net photosynthesis when measured 55, 77, and 365 DAT. Stomata1 conductance for uniconazole-treated plants was higher compared to nontreated control (0 mg·liter-1) plants when measured 49, 55, 77, and 365 DAT. Initiation of secondary xylem for stem tissues of uniconazole-treated plants was suppressed and expansion of xylem vessel length and width was less. Secondary phloem tissues of stems from uniconazole-treated plants contained larger numbers of phloem fibers having smaller cross sectional areas than phloem fibers of controls. Chemical name used: (E)-1-(p-Chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-01 (uniconazole).

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D.K. Harris, A.D. Owings, and S.E. Newman

Poinsettias and other floral crops when treated with the growth retardant uniconazole, Sumagic™, are more compact in growth habit. They have also been shown to have reduced stem strength. Calcium applied as a drench has been demonstrated to increase plant height and plant dry weight of poinsettias. Unicomazole reduced plant height without affecting dry weight. Bract color was more intense when calcium was applied as a weekly spray. Poinsettia plants had greater levels of foliar calcium when applied as a drench. Poinsettia plants sprayed and drenched with calcium and treated with uniconazole had greater levels of foliar calcium, however, this was not significantly greater than the control plants treated with uniconazole alone. The lowest level of foliar calcium was observed in uniconazole treated plants where calcium was applied as a spray. Uniconazole applications weakened the stein structure of poinsettias as with other floral crop species.

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James A. Bryan and John R. Seiler

. Schecklcr in the analysis of seedling stem anatomy; the critiques of John A. Arnone, Graeme P. Berlyn, Peter P. Feret, Stephen M. Schoenholtz, and two anonymous reviewers; and the financial support of the H. Smith Richardson Family Trust for the research

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Guochen K. Png, Katherine S. Downes, and Beng H. Tan

.02 mm using a pair of electronic calipers) of stems in each of the three IBA concentrations were assessed. Stem anatomy. Transverse slices from the middle and the tip of fresh stem cuttings were obtained by hand sectioning, and lignified cells were

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Fan Cao, Xinwang Wang, Zhuangzhuang Liu, Yongrong Li, and Fangren Peng

of adventitious roots ( Zhang et al., 2010 ). In addition, through observation, some cuttings could not differentiate from calluses. As mentioned, the stem anatomy of calluses in the stem does not inhibit differentiation, and this should be another