budbreak and poor fruit sets ( George et al., 1992 ; Olmstead, 2014 ). The use of plant growth regulators containing the active ingredient of hydrogen cyanamide (HC) to break bud dormancy and to achieve uniform budbreak has been documented for peach
Lisa Tang, Shweta Chhajed, Tripti Vashisth, Mercy A. Olmstead, James W. Olmstead, and Thomas A. Colquhoun
Yi-Lu Jiang, Yuan-Yin Liao, Meng-Tzu Lin, and Wen-Ju Yang
bud transformation was more active ( Fig. 4 ). Fig. 3. ( A ) Percentage of each bud stage on ‘Shih Hou Cyuan’ shoots before the night-breaking (NB) treatment and ( B ) percentage of floral buds emerged from stage 0, 1, and 2 buds after undergoing 3
Uttara C. Samarakoon, David J. Woolley, Ed R. Morgan, and Keith A. Funnell
within the cluster ( Samarakoon et al., 2014 ) and, based on the comparative growth potential of individual buds, could lead to differences in response to dormancy-breaking treatments. This could also influence the time needed for a bud to reach
Daisuke Sakamoto, Yuri Nakamura, Hiroyoshi Sugiura, Toshihiko Sugiura, Toshikazu Asakura, Mineyuki Yokoyama, and Takaya Moriguchi
(C18:3) by a 9-specific lipoxygenase ( Howe and Schilmiller, 2002 ) ( Fig. 1 ). In addition, applications of 10 or 100 μM KODA during paradormancy promote bud breaking in strawberry flower buds ( Fragaria ×ananassa Duchesne) (Yokoyama, personal
A. A. Gardea, Y. M. Moreno, A. N. Azarenko, P. B. Lombard, L. S. Daley, and R. S. Criddle
The increasing respiration of breaking `Pinot Noir' buds was measured by Differential Scanning Calorimetry. Bud development was classified into ecodormant, initial swelling, fully swollen, and breaking buds. Metabolic and CO2 evolution heat rates increased as the buds developed. Activation energy decreased steadily as development proceeded, which implied that less energy was required for metabolism to continue at later bud stages. A decrease in metabolic efficiency noted by a low calorespirometric ratio was observed during the transition from ecodormant to the initial swelling stage. From the second stage on, metabolic efficiency increased. The responsive nature of grape buds to warm temperatures was explained by increasing Q10 (10-20C) values from 2.8 to 3.8, 3.2, and 3.6 for the four developmental stages described above.
Humberto Nuñez and Daniel H. Díaz
Pecan has an irregular bud break under mild climate areas, difficulting pollination and reducing yields, particularly in seasons when chilling accumulation is low and when only 50% of buds open. Hydrogen cyanamide (H2C N2) at 1, 2, 4% alone or with mineral oil (MO) at 2, 4% were evaluated for their effect on lateral bud opening of `Wichita' pecans, spraying branches on january 25 or february 8. H2C N2 and its mixtures with MO advances bud break 25 and 18 days as compared to control on first and second date application respectively; by march 20th shoots on applied branches had 8-14 cm lenght while control and MO treatments had only 2-3 cm.
Initial bud break was up to 85% on treated branches as compared to 60% of control; however and regularly, some shoots emerging from buds abscise thereafter. Remaining shoot number per branch was 4.8 with 4% H2C N2 or the mixture 2% H2C N2 + 2% MO on the first application date, and with 4% H2C N2 + 2% MO on the second date, as compared to 2.5 shoots of control. A 12% bud injury occurred with 4% H2C N2 on first date application and high rates of mo of second date.
J. M. Spiers
‘Tifblue’ rabbiteye blueberry (Vaccinium ashei Reade) plants were subjected to constant and intermittent artificial chilling (7°C) and natural chilling. Insufficient artificial and natural chilling hours affected vegetative-bud break less than floral break. Plants flowered normally only after receiving 500 or more hours constant or intermittent artificial chilling. A high temperature of 23 ± 3°C when alternated with low temperature slowed, but did not nullify, the low temperature effect. A high temperature (18°C) did not nullify low temperature effects. A close association is evident between artificial constant chilling and natural chill-unit data on floral- or vegetative-bud break. Chill-unit models have potential use in predicting completion of the rest period in rabbiteye blueberry.
Naohiro Kubota and Mayumi Miyamuki
Four dormant grapevine (Vitis spp.) cultivars grown under forced conditions were treated immediately after pruning with a paste of fresh garlic, the supernatant of a 20% suspension of CaCN2, and 50% `Merit' solution a foliar fertilizer, to break bud dormancy. Garlic paste significantly accelerated budbreak and increased the rate of budbreak in three cultivars, but for `Delaware,' CaCN2 was more effective. Garlic also affected budbreak of cuttings with a single bud of `Kyoho,' `Neo Muscat,' or `Muscat Bailey A' grapes in a deep stage of dormancy. Garlic paste applied to cool `Muscat of Alexandria' vines immediately after they were pruned in various stages of dormancy (from November to March) accelerated budbreak in the spring when application was made by January. The rate of budbreak was steady, but earlier CaCN2 treatments resulted in a rate of budbreak that was not uniform, although the first budbreak was accelerated. Low concentrations of garlic juice did not promote budbreak of cuttings of `Muscat of Alexandria'. When garlic paste was applied to various parts of cuttings with two buds, budbreak was accelerated when the upper cross-section was treated, but the overall rate of budbreak was highest when the lower half of the cutting was treated. Chemical name used: calcium cyanamide (CaCN2).
J. M. Spiers and A. D. Draper
Cultivars of rabbiteye blueberry (Vaccinium ashei Reade) differed in cold requirements for bud break. ‘Woodard’ and ‘Tifblue’ plants required 400 and 600 hr, respectively, of constant chilling (6-7°C) for normal flowering. Two hundred and 400 hr of chilling, respectively, were insufficient for bud break. Additional chilling increased the amount and rate of bud break. Defoliation hastened vegetative bud break but did not affect flower buds.
Michael A. Cohen and James D. Kelley
Abscisic acid (ABA), when applied as an immersion application at 200 and 400 ppm during cold storage or as a spray application at 100 and 200 ppm at 2 stages of growth, was evaluated as an inhibitor of bud break and shoot elongation in dormant plants of Rosa cv. Helen Traubel and Syringa cv. Monge. ABA applied on 2 consecutive days at 100 and 200 ppm inhibited bud break in Rosa, but did not inhibit shoot elongation. ABA did not inhibit terminal and lateral bud break or shoot elongation in Syringa. Immersion applications at several dates during cold storage inhibited bud break and shoot elongation in Rosa and inhibited terminal and lateral bud break in Syringa. The most effective concentration in inhibiting bud break was 400 ppm. Time of application significantly affected bud break in Rosa and lateral bud break in Syringa, but did not alter shoot elongation in either plant.