Rate Of Budburst Research Articles

Índice para a avaliação da intensidade de dormência de gemas de fruteiras de clima temperado

O objetivo da pesquisa foi determinar um índice de dormência (ID) de gemas de fruteiras de clima temperado para a avaliação do teste biológico de estacas de nós isolados. Os testes biológicos foram realizados no período de abril a setembro dos anos de 2007 e 2008, com ameixeira, pessegueiro, caquizeiro, quivizeiro e videira. Com base nos valores de tempo médio para brotação (TMB), taxa final de brotação (TF), velocidade de brotação (VB), taxa de brotações vigorosas (TBV) e suas correlações, foi desenvolvido o ID para as cinco espécies. As classes de interpretação de dormência foram separadas em profunda, intensa, moderada, fraca e ausente. O ID desenvolvido para a avaliação do teste biológico de dormência de gemas de fruteiras de clima temperado demonstrou ser uma importante ferramenta para interpretação dos resultados com maior precisão.

Clinal variation of dormancy progression in apricot

The aim of this study was to determine the bud dormancy progression in apricot at different latitudes and altitudes. Six locations in regions with a Mediterranean climate in South Africa (SA) and Spain were chosen. The study was carried out during two consecutive years, 2007 and 2008, in SA and results were compared to those obtained in Spain in 2008. Locations ranged from low-chill areas, such as Ladismith and Villiersdorp in SA and Campotéjar in Spain, to high-chill areas, such as Ceres in SA and Barranda in Spain. A number of apricot cultivars comprising the range of chilling requirements in both countries were selected. In addition, a second, parallel study was performed to evaluate the paradormancy progression in ‘Palsteyn’ (SA) and ‘Rojo Pasión’ (Spain). Deeper dormancy was not observed in high-chill cultivars located in cold areas than in low-chill cultivars in warm areas. However, low-chill cultivars located in warm areas entered and released from dormancy earlier than high chill cultivars in warm areas. Thus, a clinal variation in dormancy progression under warm temperatures in apricot cultivars is suggested. The role of photoperiod and minimum temperatures is proposed to have a key role in dormancy onset. Paradoxically, an earlier maximum depth of dormancy was found in those areas with higher minimum temperatures at the end of summer. Before the beginning of winter, all cultivars showed an important increase of budburst rate, which indicated the end of endodormancy. Afterwards an ecodormancy period followed during winter, while chilling continued to accumulate. These results contrast with the assumed concept of the breaking of dormancy through chilling accumulation during winter and suggest a possible mediation by photoperiod in overcoming of dormancy. On the other hand, paradormancy exerted a reduction in budburst rate during dormancy entry, whereas decapitation increased the budburst rate throughout the dormant season, indicating interaction between different plant parts during this period.

DINÂMICA DA DORMÊNCIA DE GEMAS DE CAQUIZEIRO ‘FUYU’ EM REGIÃO DE BAIXA OCORRÊNCIA DE FRIO

O objetivo da pesquisa foi determinar a dinâmica da dormência de gemas em caquizeiros cv. Fuyu durante o outono e inverno em região de baixa ocorrência de frio. Os ramos foram coletados em 10 datas no período de abril a agosto de 2007 e 2008 em um pomar do município de Fazenda Rio Grande, Paraná. Na última coleta, um grupo adicional de ramos foi coletado e mantido em refrigerador (4 a 7 °C) por 672 h. A intensidade de dormência foi avaliada pelo teste biológico de estacas de nós isolados realizado a temperatura de 25 °C e fotoperíodo de 16 h, por meio dos parâmetros tempo médio para brotação (TMB), taxa final de brotação (TF), tempo médio para aparecimento de folhas abertas (TMFA), taxa de brotações vigorosas (TBV) e velocidade de brotação (VB). O delineamento experimental adotado foi o completamente casualizado com 11 tratamentos, quatro repetições e dez estacas por parcela. Os dois anos de avaliação foram analisados individualmente. A endodormência mais intensa do caquizeiro ‘Fuyu’ ocorre no período compreendido entre a metade de maio e o início de junho em região de baixa ocorrência de frio.

Necessidade de frio para quebra de dormência de gemas de caquizeiro 'Fuyu'

Objetivou-se, no presente trabalho, determinar a necessidade de frio para a quebra da dormência das gemas de caquizeiro 'Fuyu'. As coletas de ramos foram realizadas em cinco datas (26-04, 14-05, 21-06, 19-07 e 16-08). Foram aplicados nos ramos cinco tratamentos de frio adicional (0; 168; 336; 504; 672 h de frio) em geladeira à temperatura de 4ºC a 7ºC. A avaliação da dormência foi feita pelo teste biológico de estacas de nós isolados por meio do tempo médio para brotação (TMB), velocidade de brotação (VB), taxa final de brotação (TF) e taxa de brotações vigorosas (TBV). O delineamento experimental adotado foi o completamente casualizado, num esquema fatorial 5 x 5 (cinco datas e cinco tempos de exposição ao frio), com três repetições. Foram realizados testes separadamente com gemas terminais e com gemas laterais. A quebra de dormência de gemas laterais e terminais de ramos de caquizeiro 'Fuyu' ocorreu no mês de agosto, após o tratamento com 504 h de frio, de 4ºC a 7ºC, obtendo-se 100% de gemas brotadas.

カキ‘刀根早生’の早期加温栽培における発芽促進のための加温条件の検討

This study investigated forcing conditions for promoting bud bursting in the forced culture of the ‘Tonewase’ persimmon. Bud burst occurred earlier with the advance of the forcing starts when cuttings, with the Development Index (DVI) for endodormancy breaking of ‘Tonewase’ persimmon greater than 0.60, were forced at 18°C or 24°C. Furthermore, bud burst occurred earlier with the advance of forcing starts when cuttings, with the DVI were greater than 0.91, were forced at 11°C or 15°C. Pre-heating to 5°C or 8°C, most effective temperatures for endodormancy breaking before forcing at 15°C, similarly promoted bud burst of cuttings. The bud burst rate of cuttings was examined using pre-heating at 8°C for 9-40 days before 15°C forcing between 13 December and 12 January from 2003 to 2005. Pre-heating at 8°C for 20 days before 15°C forcing, to render the DVI as greater than 1, promoted bud burst of cuttings five days earlier compared with no pre-heating. Pre-heating of ‘Tonewase’ persimmon trees in the air temperature range between 6-8°C and 10-15°C in a greenhouse for 17-29 days induced the bud burst stage two to five days earlier compared with no pre-heating. These results suggest that, in the forcing culture of the ‘Tonewase’ persimmon, the forcing start date and set temperature can be determined according to the degree of endodormancy completion based on the DVR model, and that bud break can be further advanced by pre-heating at temperatures effective for endodormancy completion before forcing.

Freezing temperature treatment induces bud dormancy in ‘Granny Smith’ apple shoots

One-year-old, ‘Granny Smith’ apple ( Malus × domestica Borkh.) shoots were selected randomly from commercial orchards in 1999 and 2003, cold stored at temperatures between 1 and 13 °C for varied periods, following a 12/12 h freezing temperature pre-treatment of −1/13 °C (supposedly non-chilling temperatures) for 1 or 2 weeks. The rate of budburst, determined after forcing at 25 °C, was used to follow the progression of bud dormancy. The freezing pre-treatment clearly enhanced (deepened) bud dormancy in all experiments. Clearly definable influences due to the presence of leaves during the pre-treatment were not observed on shoots cold stored at chilling temperatures. Trees were defoliated before leaf drop in late summer/autumn under field conditions by hand (2001) and using a spray containing 3% urea and 1.8% zinc sulphate in 2003. In 2001 the first two hand defoliation dates significantly enhanced dormancy, while in 2003 chemical defoliation had no effect. These data indicate that the leaves are not clearly involved in the perception of factors that are responsible for dormancy induction. As with dormancy release it is possible that the perception of induction factors, i.e. low temperatures, and as shown in these data, freezing temperatures, occurs within the buds themselves.

Pruning Affects the Development of Correlative Phenomena among Lateral Shoots in Dormant Two-year-old `Royal Gala' Apple Branches

Two-year-old apple branches, ≈50 cm long, were selected from a commercial `Royal Gala' orchard in the Ceres (Koue Bokkeveld) region of the Western Cape, South Africa [33 °S, 945 m, 1500 Utah model chilling units (CU)]. In 2000, the branches received either cold storage at 5 to 7 °C or natural chilling in the field. In 2001, the trial was repeated, but only with field chilling. The branches received five dormant pruning treatments: control (not pruned); pruning back to the fourth lateral shoot (heading) before or after chilling; and removal of the second and third lateral shoots (thinning) before or after chilling. After pruning and chilling, the branches were removed from the orchard or cold room every 2 weeks and forced in a growth chamber at 25 °C. The rate of budburst (1/days to budburst) was determined for the terminal buds of the lateral shoots. Lateral shoots on the 2-year-old branches were categorized according to position: the most distal extension shoot, and all other laterals grouped. Removing distal tissue by pruning (heading more than thinning) enhanced the effect of chilling on the terminal buds on the lateral shoots and promoted budburst. Pruning was more effective before than after chilling. Pruning enhanced the growth potential of the terminal buds on proximal shoots on 2-year-old branches.

Adverse effects of high temperature on the development of reproductive organs in ‘Hakuho’ peach trees

SummaryTo examine the effect of the temperature on the development of reproductive organs, potted plants of five year old ‘Hakuho’ peach were exposed to constant temperatures of 15°C, 20°C, 25°C, 30°C, and natural conditions. The rate of flower and leaf bud burst, and flowering were recorded every day. The characteristics of reproductive organs in each treatment were examined by measuring flower size, pollen germinabitily, pollen tube elongation, development of embryo sacs, and fruit set. Percentage of flower bud bursting at 30°C was about 80% within 3 d after the onset of the treatment, while it took 18 d to reach the same percentage in the control. Flower bud break preceded leaf bud break in all treatments. Flowering was earliest at 30°C, and the period from bud burst to flowering was as short as 3–4 d. Flower sizes were significantly decreased with increasing temperature. The pollen germination was negatively affected by higher temperature, but the pollen tube elongation in the pistils was faster at higher temperatures. On the other hand, the development of the embryo sac at high temperature was considerably less satisfactory than that at lower temperature and under field conditions. High temperatures also significantly reduced the percentages of fruit set. The results suggested that the high temperature above 25°C interferes with the normal development of reproductive organs especially embryo sac, and causes poor fruit set in ‘Hakuho’ peach.

Quantification of dormancy progression in terminal apple buds. Changes in growth rate and water stratus.

During May 2000, unbranched year-old apple [Malus sylvestris subsp. mitis (Wallr.) Mansf.] shoots of the cultivars Royal Gala, Braeburn, Cripps' Pink and Granny Smith were harvested from bearing orchards in the Koue Bokkeveld, Ceres and Elgin regions of the Western Cape, South Africa, and cold stored at 4-7°C. Every two weeks two replicate bundles were removed and forced at 25°C until budburst had occurred on at least 25% of the shoots per bundle. The change In the rate of budburst over time was calculated for each orchard, and to this response either a linear or a quadratic function was fitted. Non-correlated arbitrarily chosen variables were selected from the functions. Using these variables, the orchards were separated into cluster groupings representing a dormancy pattern. First low and high chill requirement cultivars separated, followed by separation within these groups for region of origin. During dormancy in 2001, terminal buds from the same cultivars were harvested from the same orchards every two weeks and the water potential and water content was measured. A definite chilling influence was observed; water potential and content of buds from the colder Koue Bokkeveld was initially lower and increased with chilling whereas buds from the warmer Elgin showed less change in water potential or content.

Chilling period influences the progression of bud dormancy more than does chilling temperature in apple and pear shoots

SummaryOne year old, ca. 50.cm long shoots of ‘Doyenne du Comice’ pear (Pyrus communis L.) and ‘Granny Smith’ apple (Malus × domestica Borkh.) were selected randomly in autumn and winter 1999 from commercial orchards in either Elgin (348S, 320.m) or in Somerset West (34°S, 80.m), South Africa. Shoots were cold-stored at 1, 4, 7 or 10°C for periods of 0, 1, 2 or 3 months after a daily 12/12.h freezing temperature pre-treatment of 21/13°C (supposedly nonchilling temperatures) for periods of 0, 1, 2 or 3 weeks. In 2000, ‘Granny Smith’ apple and ‘Packham’s Triumph’ pear shoots were harvested in autumn from orchards in Elgin and cold-stored, without a freeze treatment, at 1, 4, 7, 10 or 13°C for periods of 0, 1, 2, 3 or 4 months. After the different treatments the shoots were forced to budburst at 25°C with continuous illumination. To determine the progression of bud dormancy, the rate of budburst, final percentage budburst, and the synchronization of budburst between shoots were used in 1999, but only the rate of budburst in 2000. In all the trials the storage period was the most important factor influencing the progression of dormancy. While in some cases the effects of both storage temperature and the freeze treatment were significant, the contribution to differences in the progression of dormancy was negligible. When our data were fitted to the chilling models currently used in South Africa the difference in temperatures between –1 to 13°C was over-emphasized relative to the period of exposure to these chilling temperatures.

Genotypic response to chilling period of apple buds from two Western Cape localities

One-year-old, ca. 40 cm long shoots of various apple cultivars were selected from commercial orchards in both the Elgin [34°S, 305 m, ca. 750 Utah Chill Units (CU)] and Koue Bokkeveld (33°S, 945 m, ca. 1300 CU) regions of the Western Cape, South Africa. Shoots were forced at a constant 25°C with continuous illumination after chilling at 4°C. The effect of chilling period on the budburst of each cultivar in both regions was estimated in 1998 and 1999 by determining: 1) % budburst; 2) the % terminal budburst; and 3) the rate of budburst [1/(days to 25% budburst)]. It was found that these indices, in reaction to chilling, differed significantly between cultivars, and within cultivars between areas. The rate of budburst was the most consistent in describing the reaction of buds to chilling and may be more useful for grouping cultivars according to chilling response.

Effects of prolonged cold storage on phenology and performance of Douglas-fir and noble fir 2 + 0 seedlings from high-elevation sources

Survival, phenology, and growth performance of 2 + 0 Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and noble fir (Abiesprocera Rehd.) seedlings planted at 1500 m in the Oregon Cascade Range were determined following a lifting on November 7 with 7 months of cold storage or lifting on March 1 with 3 months of cold storage. Storage temperature remained between 1 and 2 °C. There was no difference in Douglas-fir survival attributable to the lifting – cold-storage treatments during the first two growing seasons. The first-season survival of noble fir stored for 7 months was superior to that of those stored for 3 months, but no difference was evident after the second growing season. Timing of bud burst did not differ significantly among treatments for either species. However, the rate of bud burst was significantly greater for noble fir seedlings lifted in November and stored 7 months than for those lifted in March and stored 3 months. No difference in the rate of bud burst was observed between treatments for Douglas-fir. Shoot/root ratio for both species and treatments decreased significantly in the first growing season, but did not change significantly in the second growing season. Regardless of species, no differences were found in height growth or diameter increment between the two lifting – cold-storage treatments for the two consecutive growing seasons. The results suggest that Douglas-fir and noble fir seedlings originating from high-elevation seed sources can be lifted in fall and cold stored for 7 months without adverse effects on seedling performance.

Genecology of Bud-Burst Phenology in Douglas-Fir: Response to Flushing Temperature and Chilling

We studied the process by which bud burst of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) is synchronized to seasonal cycles. Seedlings from 23 populations were treated in 12 growth-chamber combinations of chilling periods and flushing temperatures. Bud-burst rates increased approximately logarithmically with temperature. Rates also depended on the duration of chilling, with temperature coefficients (Q10) increasing from 2.7 after 11 days of chilling to 3.5 after 77 days. The annual temperature cycle, moisture relation, latitude, elevation, and distance from the ocean of the site of origin of a population also influenced the rate of bud burst in the population under controlled conditions. The adaptive significance of these responses is discussed in terms of Levins's dormancy strategy hypothesis.