Full Bloom Date Research Articles

Use of a Phenological Model to Time Acceleration of Pollinizer Bloom

Abstract A pear anthesis phenology model was used to determine timing of placement of reflector boards near ‘Seckel’ pear trees, or polyethylene hotcaps over them to accelerate their bloom for optimum pollination of ‘Anjou’. The normal full bloom date of ‘Anjou’ was predicted from the Utah chill unit (CU) and growing degree hour (GDH) models. ‘Bartlett’ pear phenology and historical bloom divergence of ‘Seckel’ and ‘Anjou’ were used in the absence of ‘Seckel’ and ‘Anjou’ phenology to determine the timing and amount of supplemental thermal accumulation. Bloom-accelerating techniques were placed on the pollinizer trees at an intermediate anthesis stage. Polyethylene hotcaps accelerated bloom effectively.

The effect of four early spring temperature regimes on apple fruit set, tree growth and the K and Ca level in fruits

In 2 experiments, 3-year-old ‘Cox's Orange Pippin’ apple trees, still in rest, were exposed until shortly before bloom to 4 temperature treatments giving 4 patterns of bud development, i.e. rapid or slow throughout, initially rapid followed by slow, and the reverse (first slow, then rapid). During and after bloom, until harvest, all trees were kept at the same temperature. The dates of full bloom differed between treatments by as much as 14 days, but there was little variation in the number of degree-days above 5°C until full bloom. Fruit set was distinctly better when buds developed rapidly than at “slow throughout”, the other treatments occupying an intermediate position. The treatments had little or no effect on shoot growth and fruit size. The amounts of Ca per fruit increased slightly when bud development was rapid initially or throughout the pre-bloom period. For K, the data of the 2 experiments were not consistent.

Predicting the Dates of First Commercial Harvest of Selected Ontario Peach Cultivars

Abstract Multiple linear regression analysis was used to develop commercial harvest prediction dates for peach ‘Earlired’, ‘Redhaven’, and ‘Loring’. Prediction equations were developed using degree day summations and date of full bloom as variables. These equations were adjusted for geographic microclimatic variation and tested in 6 commercial peach orchards over 4 years. Predicted dates and actual first commercial harvest dates differed by 4 days or less for 100%, 96%, and 84% of the predictions for ‘Earlired’, ‘Redhaven’, and ‘Loring’, respectively.

An Evaluation of Harvest Indices for ‘Mcintosh’ Apples in Two Orchards

Abstract Harvest indices were measured in 2 mature bearing orchards of ‘Mcintosh’ apple (Malus domestica, Borkh.) in 2 seasons. Full bloom dates differed between the 2 orchards by 4 days in one season and 7 days in the other. Heat-unit accumulation during the growing season differed between the 2 orchards by 27%. The onset of the accelerated rate of ethylene production (AREP) began 133 days past full bloom in both orchards. The first significant increase in skin anthocyanin occurred before the AREP in the higher elevation orchard and after the AREP in the lower elevation orchard. Changes in flesh firmness, soluble solids, acidity, and skin chlorophyll were not significantly different before and after the AREP. The optimum harvest dates, evaluated by poststorage analysis, were on the AREP in the higher elevation orchard and after the AREP in the lower elevation orchard.

温州ミカン果実の発育と品質に関する研究

Fruit development of satsuma mandarin (Citrus unshiu Marc.) and the juice constituents were investigated throughout the growing season to elucidate the factors which determine the quality of fruit with special interest in the relationships between the time of flowering and the acid content of the fruit. In 1978, 8 trees growing in the experiment orchard of Okitsu Branch, Fruit Tree Resarch Station, were investigated. Leafy flowers, each floral branch bearing one flower and 2 to 4 new leaves, were classified into three groups according to the time of flowering-early flowers (5 days before full-bloom), intermediate flowers (full-bloom) and late flowers (5 days after full-bloom). The date of full-bloom of investigated trees was May 24.1. The earlier the flowering time the earlier the commencement of physiological fruit drop, but there was no distinct difference in the date of peak of the drop among the three groups of flowers. Intermediate-flower-fruits completed the drop first. Intermediate-flower-fruits dropped about 50 percent of their fruit which was about 15 percent less than the drop of early or late-flower-fruits.2. The rate of increment in fruit diameter was the highest on late-flower-fruits and the lowest on early-flower-fruits. It appears that the late-flower-fruits grow faster and recover the delay in relative growth. This is apparent on the longitudinal diameter of fruit as compared to the transverse diameter. Consequently, the shape index of late-flower-fruits went low very rapidly during the period from flowering to 60 days after flowering.3. The later the flowering time the fewer the number of juice sacs per 100g pulp, and accordingly, the size of the juice sacs of late-flower-fruits was larger.4. There was no difference in Brix of fruit among the three groups of flowers until late October. After that period there was a slight tendency for higher Brix in the fruits from earlier flowers. Coloring of rind commenced in late October and the fruit from earlier flowers showed advanced coloration.5. Early-flower-fruits began to decline in free acid concentration first. Five days delay in flowering resulted in five days delay in the decrease of free acid. The difference in free acid concentration among the group of flowers was maintained through most of the growing season. Citric acid showed the same transition pattern as free acid. It was concluded that the acidity of mature fruit was determined principally in rather a short period before or after flowering.6. Concentration of malic acid declined until mid-September and stayed stable thereafter. The rate of malic acid showed the lowest value in late September and there was no difference in the date among the groups of flowers.

A Statistical Method of Determining Chill Unit and Growing Degree Hour Requirements for Deciduous Fruit Trees1

Abstract Dates of rest completion are rarely available for determining the chill unit and growing degree hour requirements of deciduous fruit trees. A statistical process has been developed which permits these constants to be determined from temperature data and dates of full bloom. Bloom dates calculated from the model using the statistically derived constants compare favorably with observed dates of full bloom.

Location of Fruit on Grapevines in Relation to Cluster Size and Chemical Composition1

Abstract This paper reports an extensive study on fruiting habit of 15 grape cultivars representing different species and interspecific hybrids. Blossom records of 4 cultivars showed highly significant differences of up to 3.5 days between full bloom dates of the 1st and 4th flower clusters on a node. Significantly more crop was produced on the 9th node than on the 1st node and also on the 5th node than on the 1st node for 13 out of 14 cultivars. Only slight and generally nonsignificant differences in acid and solids content were found between fruit on the 1st, 5th and 9th nodes. With most cultivars there were significantly fewer fruit clusters on the 1st and 2nd than on the 4th to 8th nodes on a 10-node cane; numbers of fruit clusters tended to be constant from the 4th to the 9th node on a cane. Characteristic numbers of flower clusters per node are reported for different cultivars. With 8 out of 14 cultivars, wt of fruit on an individual node decreased significantly from proximal to distal cluster, in some cases the 1st cluster was more than twice the wt of the 4th. Significant decreases in solids and increases in acid content were found between proximal and distal clusters only in 4 cultivars.