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Abstract

Effects of freeze injury to the various tissues of young developing fruits were studied anatomically and illustrated by photomicrographs. Samples had been obtained just prior to the freeze so that normal and injured tissues can be compared.

In the apricot, disrupted tissue appeared in the following areas: vascular bundle tissues in the mesocarp, general destruction of the endocarp, ovullary tissue destruction with separation of the outer and inner integuments and a distinct injury occurring in the chalazal end of the ovule.

The same general pattern of tissue injury occurred for the sweet cherries as that which was evident in the apricot. However, injury at the base of the fruit was not as intense as that of the apricot. The ‘Stark Gold’ cherry, which was 2-3 days later in development than the ‘Starting Hardy Giant’, was less severely injured because the floral cup base provided some protection. It also had 4-6 hypodermal layers as compared to 2 layers in the ‘Starking Hardy Giant’.

Abstract

Morphological and anatomical development of young fruit were studied in relation to the effects of a late spring freeze. ‘Lodi’ and ‘Duchess’ apples were frozen 16 days after full bloom. Samples were collected for anatomical study on 4 subsequent dates following the freeze. The secondary vascular tissues in the outer cortex were affected, resulting in lesions in those tissues where adjacent parenchyma cells had collapsed. The main vascular strands in the outer cortex were killed, the injury extending from fruit base to apex. Separation of the hypodermis from the outer cortex occurred in the fruit apex where tissues were injured most severely. Also injuries were evident contiguous to the core line. Internal phellogen, phellem, and phelloderm in the parenchyma had formed within 18 days after injury. In some cases, cell proliferation and dedifferentiation of cortical parenchyma was noted 46 days after injury.

Abstract

A subfreezing temperature caused trunk splitting in 13-year-old apple trees of the cultivars ‘Golden Delicious’ and ‘Starking’ growing on EM VII rootstock. ‘Starkrimson’ and ‘Golden Delicious’ on a seedling rootstock and ‘Jonared’/EM VII were unaffected by the freeze. No splitting occurred below the graft union of any tree. Phloem, 8 months after the initial injury, showed extreme variation in the development of periderm throughout the injured tissues. The sieve elements, sieve plates, and phloem-ray cells in the functioning phloem were distorted and necrotic depending upon severity of injury. Cellular structure showed evidence of injury a considerable distance beyond the wound and some of the injured areas had subsequently healed. In severe but closed wounds parenchyma was the only wound tissue evident. In some cases, this tissue developed into a narrow band of phloem capable of translocation. Callus tissue formed in areas adjacent to the periderm. Dilation tissues were evident within split phloem-ray cells. In some areas the phloem-ray cells were killed and translocatable metabolites accumulated in the sieve-plate area. Some of the injured tissue was necrotic and translocation appeared impossible.

Abstract

Evaluation of plant tissues with anatomical diversity has been a long, tedious process by the conventional methods for anatomical research. Severe treatment by chemicals and heat often destroy or distort the specimen to a point where it is rendered useless. Size and number of specimens to be evaluated has also been a limiting factor for processing in anatomical studies

Abstract

The frozen section cryostat technique has been found to be of value in the preparation of many plant parts in horticultural research. This report includes those pocedures which can be readily adapted for horticultural studies, as differentiated from those that will need more experimentation. Some techniques are described that have proven successful with various tvpes of plant structures and textures studied in horticultural research programs.

Abstract

A 34°C drop in temperature from Nov. 1-8 affected plant parts of apple trees in direct proportion to vigor. More damage was evident on the shoots originating from the graft-union area than those from scaffold branches originating from the apical portions of the tree.

Abstract

An extra application of 2-(2,4,5-trichlorophenoxy)prop ionic acid (fenoprop) applied to apple trees in a commercial orchard, with an otherwise normal schedule of chemical treatment, produced abnormal fruit the following year which was unacceptable to the commercial market. The spur/pedicel development was abnormally enlarged, fruit were parthenocarpic and failed to attain normal size. The shape of the fruit was not characteristic for the cultivar. Trees were in a nonvigorous condition and would not support flower-bud formation for succeeding crops.

Abstract

Fruit spurs of apple trees on which the pedicels remained after harvest were injured by winter freeze, as illustrated by photomicrographs and by gross morphology. The fruiting spurs from which the pedicel had abscised contained a normal periderm. In the samples where the pedicel remained, extreme damage to the xylem tissue was evident.

Abstract

The ‘Lodi’ apple has heavy bearing characteristics. This study shows it to have profuse numbers of ovules compared with other commercial cultivars. The principal morphological difference between ‘Lodi’ and other cultivars is that ‘Lodi’ contains numerous smaller seeds attached to the placental tissue, not only at the proximal end, but extending all the way to the distal end.

Abstract

Development of ‘Stanley’ plum flowers and young fruits was characterized as having 6 different stages that extended from anthesis through style abscission. These stages were similar to those of peach and cherry, but growth and rapidity of development of the abscission zone differed between the 3 Prunus species. Previous research established 8 stages for cherries and 10 for peaches and apricots. The floral-cup base was enlarged adjacent to the ovary; in early, abortive fruit, remaining portions of the floral tube shrivelled, with no evidence of abscission zone formation.