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Bahget T. Hamooh and Paul E. Read

Research was conducted to further modify the forcing solution system in order to expedite the propagation of woody plants, such as Spiraea canescens, Lonicera maakii, and Cornus alba. Time of immersion in solutions containing 5 mM silver thiosulfate (STS) was compared with the basic forcing solution reported by Yang and Read (1989), a solution containing 200 mg 8-hydroxyquinoline citrate per liter and 2% sucrose. Other treatments employed were gibberellic acid (GA3) 50 mg per liter for 24 h and a combination of STS and GA3 for the same amount of time. Increasing the time in STS solution up to 24 h led to higher percent budbreak and shorter time to budbreak for all the three species examined. The combination of STS and GA3 was the most effective treatment overall in reducing time of budbreak and increasing percent of budbreak. All STS treatments studied showed similar responses in shoot elongation. However, treatments with GA3 alone, and in combination with STS showed more than a doubling in shoot length compared to all STS treatments studied and the control. Implications based on SEM observations will be presented.

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Aida M. Allam

Attempts to improve somatic embryogenesis of five pecan (Carya illinoinensis L.) cultivars using different levels of blue-green aIgal extract added to the media proved effective. WPM4-pecan media, containing 1.0 g malic hydrozide/liter and 30 g sucrose/liter, for embryo enlargement showed that the higher the extract concentration the longer the embryo harvested after 7 to 8 weeks of incubation at 22 to 25C. `Desirable' responded the best to the algal extract, where the percent elongation recorded was 129.1, 177.3, 174.2, and 200.6 for 0%, 1%, 2%, and 4%, respectively. Dessicating the embryos at 5C for 5 days enhanced the conversion on WPM4 conversion media containing silver nitrate and GA3. The number of normal shoots and roots was higher at 1% extract in cultivars Muhan, Elliot, and S-17, while the 4% algal extract was more effective for `Desirable' and `Shawnee'. Algal extract had no effect on media pH. Survival of converted embryos in the greenhouse was promising.

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Baolin Zhang and Leonard P. Stoltz

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Pauline Helen Kaufmann, Robert J. Joly, and P. Allen Hammer

The difference between night and day temperature (DIF = day - night temperature) has been shown to affect plant height. A positive DIF (+DIF), cooler night than day temperature, increases stem elongation while a negative DIF (- DIF), warmer night than day temperature, decreases stem elongation. The physiological mechanism underlying the growth response to DIF is not understood, however, and the effects of day/night temperature differentials on root permeability to water and root elongation rate have not been studied. The objective of this study was to describe how +DIF and -DIF temperature regimes affect leaf water relations, root water flux (Jv), root hydraulic conductivity (Lp), and root elongation rates of `Boaldi' chrysanthemum [Dendranthema ×grandiflora Kitam. `Boaldi' (syn. Chrysanthemum ×morifolium Ramat.)] plants over time. Leaf turgor pressure (ψp) was 0.1 to 0.2 MPa higher in plants grown in a +6 °C DIF environment throughout both the light and dark periods, relative to those in a -6 °C DIF environment. Jv differed markedly in roots of plants grown in +DIF vs. -DIF environments. Rhythmic diurnal patterns of Jv were observed in all DIF treatments, but the relative timing of flux minima and maxima differed among treatments. Plants grown in positive DIF regimes exhibited maximum root flux at the beginning of the light period, while those in negative DIF environments had maximum root flux during the first few hours of the dark period. Plants grown in +DIF had significantly higher Lp than -DIF plants. Plants grown in +DIF and -DIF environments showed differences in the diurnal rhythm of root elongation. During the dark period, +DIF plants exhibited minimal root elongation rates, while -DIF plants exhibited maximal rates. During the light period, the converse was observed. In -DIF temperature regimes, periods of rapid root elongation coincided with periods of high Jv. Results of this study suggest that negative DIF environments lead to leaf turgor reductions and markedly alter diurnal patterns of root elongation. These changes may, in turn, act to reduce stem elongation.

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Amanda Bayer, John Ruter, and Marc W. van Iersel

elongation of those internodes. Shoot dry weight was 30% less for the drought-stressed than the well-watered plants ( P = 0.037; Table 1 ). Table 1. Growth measurements for well-watered and drought-stressed Hibiscus acetosella ‘Panama Red’. Increase in

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Shuguang Wang, Yongpeng Ma, Chengbin Wan, Chungyun Hse, Todd F. Shupe, Yujun Wang, and Changming Wang

and transport, and the characteristics of their dynamic spatial changes during shoot elongation are quite limited, necessitating further investigations. The subcellular localization of endogenous IAA and its role in shoot elongation remain unclear. In

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Samir C. Debnath and Danny L. Barney

experiment was to study the effects of two zeatin concentrations for elongation of adventitious shoots. Buds and shoot clumps from leaf and stem explants of clones ‘VAME 031C’, ‘VADE 004A’, and ‘VAOF 032D’ cultured on BM with 9.1 μM zeatin were collected 10

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L.F. Rosal, J.E.B.P. Pinto, S.K.V. Bertolucci, L.C.B. Costa, and R.M. Corrêa

light at 25–30 μmol·m −2 ·s −1 ). After 45 d, the number of shoots and the average elongation of the original explants were determined. Nine of the possible 12 combinations of PGRs were assayed in five independent experiments, each involving four

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Carrie A. Radcliffe, James M. Affolter, and Hazel Y. Wetzstein

induction medium at 4 and 8 weeks. After 8 weeks on induction media, cultures were transferred to shoot elongation medium consisting of Woody Plant Medium (WPM) ( Lloyd and McCown, 1980 ) amended with 25 μM 2iP, 2 mg·L −1 glycine, 0.5 mg·L −1 nicotinic

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Xiuli Shen, Vladimir Orbović, Manjul Dutt, William S. Castle, and Frederick G. Gmitter Jr.

calculated as the percentage of explants forming shoots. Shoot elongation. Shoots that were ≈5 mm in length were excised and transferred to Magenta GA-7 vessels containing 50 mL MS medium supplemented with 0, 5, 15, or 30 μM GA 3 . Four shoots were cultured