Leaf Bud Break Research Articles

Root and Shoot Growth Response of Balled-and-Burlapped and Pot-in-Pot Sugar Maple to Transplanting at Five Phenological Growth Stages

Abstract The combined effects of phenological growth stage of a tree (e.g., bud break or bud set) and production method on plant response to transplanting are not well documented. This experiment therefore examined shoot extension, trunk diameter increase, and new root length production in balled-and-burlapped (B&B) and pot-in-pot (PIP) sugar maples (Acer saccharum Marsh.) transplanted at five different phenological stages between fall 2000 and early summer 2001 (leaf drop, root quiescence, root activation, bud break, or bud set). Growth measurements were made at bud set and root quiescence in 2001 at bud set in 2002. For B&B trees, total new root length on rhizotron windows was generally greatest for trees planted at bud break and lowest for trees planted at leaf drop. Trees transplanted at leaf drop or root quiescence had the greatest trunk diameter increase, and there was no strong effect of phenological stage at planting on shoot extension. For PIP trees, evidence was weak for a phenological stage effect on post-transplant root length production and trunk diameter increase. Trees transplanted at leaf drop or bud break had the greatest shoot extension. Overall, under the well-irrigated conditions of this study, planting at bud break resulted in the most favorable transplant response for B&B trees, and PIP trees appeared to transplant with equal success at all phenological stages, including after bud set in July.

Maturation of Thyriothecia of Schizothyrium pomi on the Reservoir Host Rubus allegheniensis.

Flyspeck disease caused by the Ascomycete fungus Schizothyrium pomi is a major component of a summer disease complex that has become an increasing problem on apple in the northeastern United States. This study describes the development of thyriothecia of S. pomi on one of its major reservoir hosts, wild blackberry, and suggests that temperature drives thyriothecium maturation. An empirical model relating thyriothecium maturity to degree-days from apple leaf budbreak in Massachusetts had a high coefficient of determination, R2 = 0.90. Ninety percent of thyriothecia matured between 540 and 1,625 degree-days from the budbreak biofix. S. pomi produced one generation of asci per year on blackberry. This discrete maturation period occurred well before signs of disease developed on apple fruit and before production of conidia. Considering that fungicide applications for scab management in commercial apple orchards also will protect fruit from flyspeck during early fruit development, it is unlikely that ascospores produced on reservoir hosts directly infect fruit. Instead, they probably initiate infections in reservoir hosts adjacent to commercial orchards, which produce conidia that are the inoculum which infects apple fruit in commercial production.

Preformation in vegetative buds of Prunus persica: factors influencing number of leaf primordia in overwintering buds

We investigated the influence of bud position, cultivar, tree age, tree carbohydrate status, sampling date, drought and light exposure on the number of leaf primordia formed in dormant vegetative peach buds (Prunus persica (L.) Batsch) relative to the number of primordia formed after bud break (neoformed). During winter dormancy, vegetative peach buds from California and Italy were dissected and the number of leaf primordia recorded. Between leaf drop and bud break, the number of leaf primordia doubled from about five to about 10. Parent shoot length, number of nodes on the parent shoot, cross-sectional area of the parent shoot, bud position along the parent shoot and bud cross-sectional area were correlated with the number of leaf primordia. Previous season light exposure, drought and tree carbohydrate status did not affect the number of leaf primordia present. The number of leaf primordia differed significantly among peach varieties and tree ages at leaf drop, but not at bud break. Our results indicate that neoformation accounted for all shoot growth beyond about 10 nodes. The predominance of neoformed shoot growth in peach allows this species great plasticity in its response to current-season conditions.

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.

Epidemic Development of Hawthorn Leaf Blight (Monilinia johnsonii) on Mayhaw (Crataegus aestivalis and C. opaca) in Georgia.

Mayhaws are small trees and shrubs in the hawthorn genus, Crataegus. They are native to the southern United States, where their fruit is highly valued for use in jellies and preserves. Since 1997, symptoms of hawthorn leaf blight, caused by Monilinia johnsonii, have been observed in mayhaw orchards in southwestern Georgia. We studied epidemic development of the disease in a mixed planting of Crataegus aestivalis (eastern mayhaw) and C. opaca (western mayhaw) between 2000 and 2002. Apothecia of M. johnsonii were first observed in early to mid-February on overwintered, mummified fruit of C. aestivalis; no apothecia were detected in plots underneath C. opaca trees. Both mayhaw species exhibited moderate to severe leaf blighting beginning in early March, although some genotypes within each species apparently escaped primary infection via delayed leaf bud break or a slower rate of leaf expansion. On a per-tree basis, leaf blight incidence was positively correlated with mean leaf length during the period when apothecia were most numerous (r = 0.7225, P = 0.0003, n = 20). Fruit mummification, which results from secondary infection of open flowers by conidia, was widespread by late March to early April and was significantly (P < 0.05) more severe on C. aestivalis, most likely because trees of this species were at an earlier bloom stage when conidia-bearing blighted leaves were first observed. By contrast, C. opaca advanced through bloom earlier, thereby partly escaping secondary infection. On a per-tree basis, there was no relationship between incidence levels of leaf blight and fruit infection for either species; indeed, some trees with the lowest incidence of leaf blight had the greatest incidence of fruit mummification and vice versa. Thus, in a mixed planting of different mayhaw genotypes, conidia appear to be dispersed readily from heavily blighted trees, leading to high levels of fruit infection even in trees with negligible incidence of leaf blight. There are genotypes within both mayhaw species that almost completely avoid either primary infection or secondary infection; therefore, planting such genotypes in pure stands may aid in minimizing losses due to the disease.

Phenological modifications in plants by various edaphic factors.

Various mechanical, chemical and physical soil analyses were carried out, in addition to weather observations, for 3 years at several sites along an oceanic-continental gradient in a fjord district in western Norway. All the environmental factors observed were correlated with the spring and a few late-season phenophases of many native and cultivated woody plants and some herbs by simple, linear correlations and by stepwise multiple and partial analyses. Different techniques were used to try and eliminate many intercorrelations between various environmental factors. As expected, air temperature measurements in nearly all analyses from these temperate region districts gave the most significant correlations with the phenology of the plants, the temperature during the night generally being the most important in mainly vegetative periods, e.g. to leaf bud break in spring, and the temperature during the day affecting the more generative phases, such as the period between leaf bud break and flowering. The other environmental factors, however, showed strong variation in correlation significance among the various species studied and also with different phenophases of the same species. Various hypotheses are put forward to explain such variation. Air humidity (including precipitation) and/or soil moisture (including intercorrelated parameters, e.g. soil grain size and bulk density) were relatively often found to be of importance. In the stepwise multiple analyses for leaf bud break of the birch (Betula pubescens), for instance, the amount of precipitation was the second factor to enter the analyses by a positive correlation with the developmental rate, after the most important factor, the night temperature. Positive correlations with a high clay content and bulk density in the soil indicated that high soil moisture is also favourable for early bud break in the birch. Other phenophases that seemed to be favoured by a good water supply were leaf bud break of the bird cherry (Prunus padus) and rowan (Sorbus aucuparia), and flowering of the hazel (Corylus avellana), common lilac (Syringa vulgaris), plum ('Victoria') and currant ('Red Dutch') and also, to some degree, the goat willow (Salix caprea). The amount of ions (P, K, Mg and Ca) often showed negative correlations with the developmental rate, particularly of earlier phenophases of both native and cultivated plants (except for the apple 'Gravenstein' and pear 'Moltke'), possibly, indicating that a high nutrient level delayed plant development. A similar explanation might be given for the observation that high pH in the soil often seemed to delay plant development (leaf bud break of Betula, Sorbus, Syringa and plum, and flowering of Corylus, bluebell (Campanula rotundifolia) and red currant). According to the analyses there seemed to be a tendency for plants that are particularly dependent on warm weather for leaf bud break, e.g. the ash (Fraxinus excelsior), and flowering, e.g. Prunus, pear, apple and, to some degree, the raspberry ('Preussen'), to be less dependent on other environmental factors for their development. For instance, if there were any effects of water for these plants, they were negative for moisture and soil factors intercorrelated with water.

Heritability, variance components and correlation of morphological and phenological traits in hazelnut

AbstractMost traits of interest in hazelnut are quantitative, yet there is little information available on heritability, variance components, or correlations. In this study, 13 morphological and four phenological traits were observed for 3 years on 41 parental genotypes, and for 2 years on seed‐lings representing 35 progenies. Narrow‐sense heritability estimates obtained by regression of offspring means on midparent values were all high, ranging from 0.56 for amount of kernel fibre to 0.89 for nut depth. Data on the parent genotypes was used to analyse variance components and showed that genotypic variance accounted for most of the phenotypic variance for all traits, and there was very little variation among trees within genotypes. Genotype‐year interaction accounted for only a very small part of the phenotypic variance for most traits, and changes in genotype rank were few and minor. Thus, selection based on genotype means is appropriate. The largest genotype‐year interaction components were observed for time of nut maturity, time of stigma exsertion, time of catkin elongation, number of nuts per cluster and amount of kernel fibre. For these five traits, evaluation over a period of years is advised. Correlation coefficients were large and positive for four nut size traits, indicating some redundancy in these measurements. Three of the phenological traits (time of stigma exsertion, time of catkin elongation, and time of leaf budbreak) were also highly and positively correlated. A large genetic correlation (0.44 &lt; r &lt; 0.73) was noted between good blanching and early phenology (catkin elongation, stigma exsertion and leaf budbreak), although plots of individual seedling values showed a large degree of scattering. Genetic correlations also indicated that seedlings with small nuts also tend to have compressed nuts, short husks and catkins that elongate later, but plots of individual seedling values showed large scattering. Correlations among the six traits directly related to the objectives of the Oregon State University hazelnut breeding programme (kernel weight, per cent kernel, nut shape index, blanching ability, relative husk length and nut maturity) were very low, indicating that they can be handled as independent traits.

Starting dates and basic temperatures in phenological observations of plants

Several methods have been used in plant phenology to find the best starting date in spring and the best threshold or basic temperature for growth and development of perennial plants. In the present paper the date giving the highest correlation coefficient for development to various phenophases, in relation to 24-hourly mean air temperatures was chosen as the best starting value in further analyses. For many woody plants this date was very often found to be 1 April based on phenological and climatological observations at about 60 sites in western Norway (at about 61°N). The early flowering species Corylus avellana and Salix caprea and the early leaf-bud breaking Prunus padus seemed to start development earlier in Spring, while the late sprouting Fraxinus excelsior showed the highest correlation coefficient using 15 April. If daytime temperatures were used in the calculations, the ”best” starting date was generally found to be later than for the 24-hour mean temperatures. This variation must be seen as resulting from the different basic temperatures for the development of various species. Estimates of basic temperatures in various species and periods may be given, for example by finding the value having the least variance in heat sums or by various regression analyses. A technique has been developed to minimise the influence of significance of correlation, using the intercept with the temperature axis by merging the two least squares rectilinear regression lines that can be found between plant development and mean air temperature (from the estimated best starting date) at r=+1 or –1. The basic temperature seemed to vary from –5.9°C for leaf-bud break of P. padus to 5.5°C for leaf-bud break of F. excelsior, with basic temperatures of several other woody plants having intermediate values. These values are compared with those found by other methods.

The Effect of Timing of Dormex Application on Blueberry Leafing and Flower Mortality

Leaf bud development is a problem on many blueberry cultivars grown throughout the Southeast. Dormex (50% hydrogen cyanamide) has shown potential in accelerating leaf and floral bud development of some fruit crops, but its usage on blueberries has not been thoroughly explored. A greenhouse experiment was conducted to examine the effects of timing Dormex applications on `Climax' rabbiteye blueberry (Vaccinium ashei) and `Oneal' southern highbush blueberry (V. corymbosum). Plants were subjected to low and moderate chilling conditions and were forced under greenhouse conditions. Dormex timings were: 1)1 day after forcing (DAF), 2) 3 DAF, 3) at 10% stage 3 floral buds, 4) at 30% to 50% stage 3 floral buds, 5) at 10% to 30% stage 4 floral buds, 6) control (no Dormex). All Dormex applications were applied at a rate of 2% product. Results showed that Dormex both increased and accelerated leaf bud break as compared to the control. However, flower buds at stage 3 of development or beyond were very susceptible to chemical burn by the product. The data indicate that timing of Dormex applications on blueberries should be based on rate of plant development rather than calendar time. Additional research is needed to most effectively use the product to aid blueberry leaf development.

Ambient biogenic hydrocarbons and isoprene emissions from a mixed deciduous forest

Experiments were conducted during the growing season of 1993 at a mixed deciduous forest in southern Ontario, Canada to investigate the atmospheric abundance of hydrocarbons from phytogenic origins, and to measure emission rates from foliage of deciduous trees. The most abundant phytogenic chemical species found in the ambient air were isoprene and the monoterpenes α-pinene and β-pinene. Prior to leaf-bud break during spring, ambient hydrocarbon mixing ratios above the forest remained barely above instrument detection limit (∼20 parts per trillion), but they became abundant during the latter part of the growing season. Peak isoprene mixing ratios reached nearly 10 parts per billion (ppbv) during mid-growing season while maximum monoterpene mixing ratios were close to 2 ppbv. Both isoprene and monoterpene mixing ratios exhibited marked diurnal variations. Typical isoprene mixing ratios were highest during mid-afternoon and were lowest during nighttime. Peak isoprene mixing ratios coincided with maximum canopy temperature. The diurnal pattern of ambient isoprene mixing ratio was closely linked to the local emissions from foliage. Isoprene emission rates from foliage were measured by enclosing branches of trees inside environment-controlled cuvette systems and measuring the gas mixing ratio difference between cuvette inlet and outlet airstream. Isoprene emissions depended on tree species, foliage ontogeny, and environmental factors such as foliage temperature and intercepted photosynthetically active radiation (PAR). For instance, young ( 3 months old) leaves. During the latter part of the growing season the amount of carbon released back to the atmosphere as isoprene by big-tooth and trembling aspen leaves accounted for approximately 2% of the photosynthetically fixed carbon. Significant isoprene mixing ratio gradients existed between the forest crown and at twice canopy height above the ground. The gradient diffusion approach coupled with similarity theory was used to estimate canopy isoprene flux densities. These canopy fluxes compared favorably with values obtained from a multilayered canopy model that utilized locally measured plant microclimate, biomass distribution and leaf isoprene emission rate data. Modeled isoprene fluxes were approximately 30% higher compared to measured fluxes. Further comparisons between measured and modeled canopy biogenic hydrocarbon flux densities are required to assess uncertainties in modeling systems that provide inventories of biogenic hydrocarbons.

Contribution of Storage and Currently Assimilated Nitrogen to Vegetative and Reproductive Growth of Rabbiteye Blueberry

The relative contribution of storage and currently assimilated N to reproductive and vegetative growth of `Bonita' and `Climax' rabbiteye blueberry (Vaccinium ashei Reade) was estimated immediately before and during the fruit development period. Total and storage N decreased in roots and shoots of both cultivars during dormancy and early fruit development. The principle N storage form appeared to be protein, as indicated by a significant decline in total shoot and root protein during this same period. Storage N from roots and shoots in both cultivars was remobilized to flowers and/or fruit and new vegetative growth. At anthesis, 90% of the total N present in reproductive organs was estimated to come from storage N. By fruit maturity, ≈ 50% of the accumulated N was derived from storage pools. Storage N contributed 90% of the total N in developing vegetative growth of `Bonita' at leaf budbreak, which is concomitant with floral budbreak for this cultivar. Developing vegetative growth of `Climax' at leaf budbreak, which occurs ≈ 4 weeks after floral budbreak, derived ≈ 65% of its total N from storage and 35% from currently assimilated N. By fruit maturity, contribution of storage N to new vegetative growth had decreased to ≈ 20% in both cultivars, indicating that currently assimilated N became the principal N supply as vegetative growth became more established. Differences in timing of floral and vegetative budbreak between the two cultivars did not appear to affect allocation of either storage or currently assimilated N to new vegetative or reproductive growth.

Relationship of Flowering Time, Rate of Seed Germination, and Time of Leaf Budbreak and Usefulness in Selecting for Late-flowering Apples

The relationship between dormancy of seeds and buds of apple (Malus × domestica Borkh.) might provide breeders with an early opportunity to select for delayed development. Seeds of late-flowering genotypes require much longer exposure to chilling temperatures than those of early flowering” genotypes, and they germinate over a much longer period. In three progenies that exhibit much variation for the two traits, seed germination time was correlated with time of leafing-out of the resulting seedlings, and could be used to select for delayed budbreak. However, selection would be ineffective when little genetic variation for seed germination and budbreak is present. Leafing-out ratings in the nursery in the 2nd year were highly correlated with those in the 3rd year, indicating that selection for late leafing in the nursery during the 2nd year would be more effective than selection based on seed dormancy, especially in progenies exhibiting little genetic variability for this trait. Breeders can effectively use both relationships by first eliminating early germinating seeds and then eliminating early leafing seedlings.

EFFECT OF HYDROGEN CYANAMIDE (DORMEX) SPRAYS ON PEACH TREES SUFFERING FROM LACK OF WINTER CHILLING.

Lack of winter chilling (480 hrs. at or below 7.2°C by 02/28/89) occurred along Alabama's Gulf Coast in the winter of 1988-89. Varieties requiring 650 hours of chilling or more were under stress. To evaluate hydrogen cyanamide (HC), a product used world wide to replace part of some fruit plants chilling req., a study was conducted along the Gulf Coast using Bicentennial (700 hr.), Sentinel (850 hr.) and Loring (900 hr.) peach varieties. Full tree sprays (applied to drip with handgun) using 0, .5 and 1% a.i. plus .25% × 77 were applied 03/01/89. Fruit buds were dormant to slight swell when sprayed. HC greatly enhanced rate and % of leaf bud break at the 1% conc., for all varieties. Rate and % of flowering were significantly increased at 1% conc. in Loring and Sentinel but nearly all fruit dropped. Flowering, yield and fruit size of Bicentennial-were significantly improved at .5 and 1% conc. HC was effective in replacing lack of chilling in this variety.

Quantitative Chilling Enhancement and Negation in Peach Buds by High Temperatures in a Daily Cycle1

Abstract The effect of exposure of small peach plants (Prunus persica (L.) Batsch cvs. Redhaven and Redskin) to daily fluctuating temperatures (16 hours low: 8 hours high) of 6-15°, 6-18°, 6-21° and 6-24°C was examined in comparison with continuous chilling at 4° and a non-chilled control. Even though all chilling treatments received the same amount of chilling (weighted chilling hours), good leaf bud break was obtained only in the continuous 4°, 6-15° and 6-18° treatments. No lateral leaf buds opened in the 6-21°, 6-24° or the non-chilJed controls of both cultivars. The 6-15° temperature regime was more efficient than continuous chilling in breaking bud rest on a weighted chilling hour basis. ‘Redskin’ lateral buds were shown to have a higher chilling requirement than ‘Redhaven’. Terminal buds especially of ‘Redhaven’ showed a very low chilling requirement. Treating plants with 50 or 150 mg/liter GA3 slightly advanced bud break but did not affect the level of sprouting.

The Effect of Temperature on the Activity of Oil + Dinitro-o-cresol Sprays to Break the Rest of Apple Buds1

Abstract Promotion of leaf bud break in ‘Golden Delicious’ apple by a mineral oil and dinitro-o-cresol (DNOC) combination spray depended on day-time temperature. Higher temperatures during the first 2 weeks after spraying increased the level of bud break. The highest temperature tested, 30°C, most effectively promoted lateral bud break.

The Effect of Climatic Conditions on Dormancy Development of Peach Buds. I. Temperature1

Abstract With controlled temperatures low temperature efficiency in releasing peach buds from dormancy follows an optimum curve in which 6°C is the optimum for average lateral leaf buds and 10°C is about half as efficient. “Weighted chilling hours” instead of “chilling hours” was proposed as a chilling measurement criterion. A high temp of 21°C, when alternated daily with low temp, nullified the low temp effect; a high of 18°C had no effect. Interrupting the chilling by 2 separate periods of 11 and 12 days at 20°C did not show any nullifying effect, but greatly enhanced lateral leaf bud break.

The Effect of Limitation in Light During the Rest Period On Leaf Bud Break of the Peach (Prunus persica)

AbstractReduction in the amount of light supphed during the mid‐rest period caused a hetter leaf bud opening in the peach as compared with natural winter daylight; this includes darkness, short photoperiod and reduced light intensity. The quantitative nature of this light effect was shown. The role of light as a factor regulating dormancy is discussed.

Plant Growth Regulation by Stimulation of Ethylene Production

A recently released growth regulator, Amchem 66-329, produces several plant responses suggestive of ethylene effects, including induction of leaf epinasty, bud break, abscission, and pineapple flowering. We find that this growth regulator is highly active in the stimulation of ethylene production in pea seedlings, and suggest that the regulation of growth is achieved through the stimulated ethylene production. 5 references, 3 figures, 1 table.

The Role of Light in Leaf and Flower Bud Break of the Peach (Prunus persica)

AbstractThe effect of light on peach leaf and flower bud break was examined. It was found that leafless dormant shoots were light‐perceptive organs. Darkness, after light preconditioning during dormancy, reduced leaf bud opening; however, light was obligatory when the shoots were preconditioned in the dark. Relatively short exposures to light were sufficient to stimulate leaf bud break. Terminal buds were less inhibited by darkness than were laterals. Flower bud break was inhibited in light after dark preconditioning. The red region of the spectrum was found to be active; the phytochorome system seems to be involved in the light reactions, as the red light effect was reversible with subsequent far‐red illumination. Supplementary light, producing long‐day conditions, could partly compensate for insufficient chilling. A possible sequence of reactions in the plant is suggested.