Graduate Thesis Or Dissertation

 

Influence of canopy orientation on fruiting of 'Ànjou' pears and postharvest urea spray on ovule longevity and fruit set of 'C̀omice' pears Public Deposited

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  • The effect of canopy orientation on fruiting performance of 'Beurre d'Anjou' pears (Pyrus communis L.) and postharvest urea spray on ovule longevity and fruit set of 'Doyenne du Comice' pears were studied. Hedgerows of 'Beurre d'Anjou' pear trees planted in 1969 in two orientations north-south (N-S) and east-west (E-W) were used to study the effect on pear fruiting. The trees were spaced 1.3 x 3.7 m, trained to a central leader, and mechanically pruned to a tree wall 3.7 m high and 1.8 m wide at the base with a wall angle of 170 from the vertical. Flower density (FD), flower buds per unit branch cross-sectional area (BCSA), was lowest on the N wall of the E-W rows in 1990 and on the S wall of the same rows in 1991. In both years, N-S rows had higher FD. Fruit set (FS), fruit per flower buds, was highest on the S wall and lowest on the N wall of the E-W rows, whereas, the E and W walls of the N-S rows were intermediate. Crop density (CD), fruit per unit BCSA, had a similar pattern as FS with more fruits on the S wall and less on the N wall of the E-W rows. However, CD was more evenly distributed between the walls of the N-S hedgerows. Differences in FS and CD between sides were correlated to different levels of sunlight interception. For instance, the mid height of the N wall of the E-W rows received less than 20% full sunlight throughout the growing season whereas the S wall received more than 35% of irradiance especially towards the equinoxes. Increased solar heating on the S and W walls late in the season led to more sunburned fruits. Fruits from E-W rows were larger and less firm. 'Doyenne du Comice' is generally considered as a commercial pear variety with highly palatable fruits. A shortcoming of this variety is, however, that its trees come into bearing late and then set a small crop. The possibility of altering ovule longevity and fruit set of this cultivar by nitrogen fertilization was investigated. Mature trees were given a single foliar application of 5% or 10% urea immediately after harvest. Ovule senescence was detected by fluorescence microscopy. Ovule longevity was extended in both treatments in comparison to control. FS was increased after a foliar application of urea when based on trunk cross sectional area. There was no effect on FD, CD, fruit fresh weight, and yield efficiency of 'Comice' trees treated with postharvest urea sprays.
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