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Hailin Liu, Cunmeng Qian, Jian Zhou, Xiaoyan Zhang, Qiuyue Ma and Shuxian Li

( Holzmueller et al., 2007 ; Thomas, 1969 ). Typically, C. florida is propagated from seeds, but the seeds usually develop strong dormancy ( Coartney et al., 1989 ), which may be a great challenge for seed reproduction ( Dirr and Heuser, 1987 ). Studied with

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J. Rodriguez-A., W.B. Sherman, R. Scorza, M. Wisniewski and W.R. Okie

The evergreen (EVG) peach, first described in Mexico, was used as a parent with deciduous (DE) peaches to develop F1 and F2 hybrid populations in Mexico, Florida, Georgia, and West Virginia. F1 trees were DE and F2 plants segregated 3 DE: 1 EVG. In West Virginia, the most temperate location, the heterozygous class could be distinguished in the first few years of growth by late leaf abscission in the fall. Segregation ratios suggest that the EVG trait is controlled by a single gene, evg, the EVG state being homozygous recessive. Evergreen trees were characterized by insensitivity of shoot tips to daylength and failure of terminal growth to cease growth until killed by low temperature. Lateral buds of EVG trees went dormant in the fall. Deep supercooling occurred in both EVG and DE trees, but it appeared later in EVG trees, was of shorter duration, and occurred to a lesser extent. Evergreen germplasm may be useful in developing peach cultivars for frost-free subtropic and tropical areas. It also presents a useful system for studying dormancy and cold hardiness.

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Yi Zhang, Tracey Mechlin and Imed Dami

Stoddart, 1980 ). Additionally, ABA has been suggested as a dormancy-inducing hormone because it accumulates in dormant nodes and increases after the tissue is exposed to low temperatures ( Dogramaci et al., 2010 ). The variation of ABA concentration in

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Uttara C. Samarakoon, David J. Woolley, Ed R. Morgan and Keith A. Funnell

capable of developing into flowering shoots. Flowering shoots of gentian develop from the overwintering crown buds produced in the previous growing season. Crown buds are dormant in winter until growth recommences in spring when they emerge, with floral

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Takashi Hosoki

Effects of methyl disulfide (MeS2) on sprouting and phytohormones in dormant corms of spring-flowering gladiolus (Gladiolu×Tubergenii Hort. `Charm') were studied. Corms treated with MeS2 sprouted 30 days earlier than nontreated corms. The concentrations of endogenous promoters in the corm tissue increased and inhibitors decreased within 24 h of treatments. High concentration of inhibitors were present in the nontreated corms.

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Kil Sun Yoo, Leonard M. Pike and B. Greg Cobb

Inner scales excised from dormant bulbs of the short-day `Texas Grano 1015Y' onion (Allium cepa L.) were cultured in vitro and leaf growth was examined. Light promoted leaf growth, but no differences in leaf growth were observed for media pH between 4 and 7. Leaf growth rate in darkness was highest at 24C, reduced at 15C, and greatly reduced at SC. Kinetin promoted leaf growth at 1, 10, and 100 μm. IAA was effective at 1 and 10 μM, but not at 0.1 and 100 μm. GA3 promoted growth at 0.1 μM. No inhibitory effects of ABA on leaf growth could be detected. Chemical names used: 1-H-indole-3-acetic acid (IAA), abscisic acid (ABA), gibberellic acid (GA3), 6-furfurylaminopurine (Kinetin).

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Anwar A. Khan

158 WORKSHOP 24 Quantification of Plant Dormancy

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Dehua Liu, Miklos Faust, Merle M. Millard, Michael J. Line and Gary W. Stutte

Magnetic resonance imaging was used to determine water states in paradormant apple (Malus domestica Borkh.) buds and during early events when buds resumed growth. Proton density and states of water were determined by creating image maps of proton density and relaxation times (T2). Summer-dormant (paradormant) buds had T2 relaxation times up to 30 ms. This water in bud tissues is considered relatively free compared to water that had T2 relaxation times of <1 ms in other parts of the stem and bark. Buds were forced to grow either by pruning off the terminal bud or by starting the bud with thidiazuron (TDZ). Both treatments gave essentially the same results. After treatment, buds started to grow immediately and water moved into the stem and into the bud. As there was more free water in the bud, T2 values ranged up to 50 ms. There appeared to be an inhibitory gradient down on the shoot, which was removed temporarily by excising the top bud. However, between the 2nd and 10th day after removal of the top bud this dominance was reinstated by the highest bud on the stem, which eventually formed a shoot. TDZ treatment overcame this inhibitory gradient effect. There was also a growth potential gradient coinciding with the inhibitory gradient. The growth of lower buds was much slower than that of the upper buds. The growth potential gradient was not overcome by TDZ treatments.

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L.H. Fuchigami and M. Wisniewski

158 WORKSHOP 24 Quantification of Plant Dormancy

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Miklos Faust

158 WORKSHOP 24 Quantification of Plant Dormancy