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In deciduous fruit trees, some storage reserves accumulate during fall and are used for early spring growth. In sweet cherry (Prunus avium L), stored reserves are critical for early growth and there is a transition phase during which current photoassimilates become the primary source for support of reproductive and vegetative sinks. As little is known about this transition, an experiment using 4-year-old `Regina' sweet cherry on the semidwarfing rootstock, Gisela 6, was established. Using whole canopy exposure chambers, five trees were pulsed with high levels of 13CO2 on three different dates during fall (Sept.-Oct). At leaf drop, leaves, buds, wood, bark and roots were sampled for GCMS analysis of pre-winter storage reserves. The major storage organs (those which had the highest change in isotopic ratios) were roots and wood in the trunk and branches. During spring, newly developing organs (flowers, fruits and young leaves) were sampled weekly from bloom to stage III of fruit development for additional GCMS analysis. The stored 13C was mobilized and partitioned to flowers, fruits and young leaves from early spring until one week after fruit set. The highest 13C levels in growing sinks were observed between bloom and fruit set. The isotopic composition of new organs did not differ initially (3 May). During the three next sampling dates (10-24 May) reproductive organs had higher 13C levels compared to vegetative growth. The role of storage reserves, as a source of assimilates for early spring growth and their implications for crop development, will be discussed.

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Endodormant `Hawthorne' peach shoots were collected in early autumn and sectioned into long (30-40 cm), short terminal (10-15 cm), or short sub-terminal (IO-15 cm) cuttings. Dormancy-breaking treatments included application of hydrogen cyanamide H2C N2), thiourea (TU), sodium azide (NaN3) or gibberellic acid (GA3) solutions; atmospheric methyl jasmonate (MJ); hot water (50C for 1-2 h); or chilling (3.5C for 1-4 weeks). During forcing at 24C, & budbreak of all bud types on long cuttings was very low. On short cuttings, % apical budbreak was greater than % lateral vegetative budbreak, with almost no floral budbreak. Relative to H2CN2-induced lateral vegetative budbreak, budbreak induced by MJ, TIJ, GA,, and NaN3 was 17, 34, 50, and 92%, respectively. Relative apical budbreak was 0, 95, 53, and 63%, respectively. Addition of aminooxyacetic acid (AOA) to the beaker solution (in which cuttings were forced) induced apical, but not lateral, budbreak by itself; AOA synergistically improved H2CN2-induced budbreak by 23%. Latetal budbreak on short sub-terminal cuttings treated with hot water (1 h) was similar to that of H2CN2 treatment. Chilling increased apical budbreak to 100% as duration increased to 3 weeks, lateral vegetative budbreak only reached 43% after 4 weeks of treatment. The use of different bud and cutting types as model systems to study the differential regulation of dormancy by various treatments will be discussed.

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Priming regimes were evaluated on pansy seeds (Viola ×wittrockiana Gam. `Crystal Bowl Sky Blue') in high-temperature germination tests. Priming regimes evaluated included CaCl2, MgCl2, K2HPO4, Na2HPO4, NaCl, KCl, KNO3, Na2SO4, and polyethylene glycol 15,000 (PEG15,000) at –1.0 and –2.0 MPa, for 3, 6, or 9 d at 23 °C. Primed and nonprimed control seeds were then germinated at 25, 30, or 35 °C. Total percent germination of nonprimed control seeds was significantly less at 35 °C than at 25 °C. Seeds primed with CaCl2 at –1.0 MPa for 3 d at 23 °C had significantly higher germination at 35 °C than all other priming regimes tested, including aerated PEG8000 at –1.0 MPa for 7 d at 15 °C. Seed respiration, measured by O2 uptake, during germination of seeds primed with CaCl2 was higher than for control seeds or those primed with PEG8000. Priming pansy seed with CaCl2 at –1.0 MPa for 3 d at 23 °C was effective in increasing seedling emergence and for reducing the time of emergence in summer greenhouse studies.

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Abstract

At last year's W-130 Regional Project meeting in Penticton, B.C., Edward L. Proebsting, Jr., chairman of the meeting, requested that we communicate our interest and discussion in the Oct. 1985 Viewpoint article by Lang, Early, Arroyave, Darnell, Martin, and Stutte concerning dormancy terminology (HortScience 20:809–812).

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