Search Results

You are looking at 11 - 15 of 15 items for :

  • Author or Editor: Roger Young x
  • Journal of the American Society for Horticultural Science x
Clear All Modify Search
Authors: and

Abstract

Sour orange leaves (Citrus aurantium L.) from cold-hardened and unhardened plants were sectioned and prepared for light and electronmicroscopy examination after freezing at -3.3°C and -6.7°. Severe membrane destruction was visible in both hardened and unhardened cells after freezing. These membranes included the tonoplast, outer chloroplast membrane, and the cristae membrane in the mitochrondria. The thylakoids of the grana, the intergrana lamella, and the outer mitochrondrial membranes remained intact. Membrane destruction resulted in gross disorganization of cell contents. Disruption of cells was evident and included palisade and mesophyll cells, the lower epidermal layer, and xylem, fiber, and pith cells in the vascular system.

Open Access
Authors: and

Abstract

Preharvest applications of (2-chloroethyl)phosphonic acid (ethephon) on ‘Bearss’ lemons were relatively ineffective for inducing degreening or abscission. This was not due to lack of absorption or ethylene production. Similar rates of application as a postharvest dip induced degreening, suggesting that a factor from the tree inhibited the response to ethylene. This possibility was supported by data from further tests on ‘Bearss’ lemons and on ‘Robinson’, ‘Lee’, and ‘Dancy’ tangerines and ‘Hamlin’ oranges. Degreening and abscission responses to ethephon in detached fruit or fruit on which the stem was girdled were greater than in fruit on the tree. Applications of gibberellic acid retarded these responses. The results varied among cultivars and between the degreening and abscission responses. However, the general response pattern suggests that the tree provides a factor (or factors) which, on translocation to the fruit, inhibits degreening and abscission. This inhibitory factor may be a growth promoter such as auxin, gibberellin, or cytokinin.

Open Access

Abstract

‘Redblush’ grapefruit borne on young fruiting trees and grafted on sour orange seedlings were exposed to natural and artificial climates. Fruit exposed to artificially controlled and naturally occurring minimum night temperatures above 70°F, combined with high day temperatures, had high Brix contents, low acid, and thin but green peels. Fruit exposed to minimum night temperatures below 60°, combined with moderate to cool day temperatures had both high Brix and acid and thicker but better colored peels. Cool temperatures in the late fall after hot summer and early fall conditions aided in thickening and coloring of peels of fruit which had already attained high Brix and early maturity.

Open Access

Abstract

14C-Ethylene was the major breakdown product of 1,214C-(2-chloroethyl)phosphonic acid (ethephon)-treated fruit and leaves of several Citrus taxons. Neither 14CO2 nor other by-products were detected. Most of the nonethylene radioactivity recovered was from tissue surfaces. Radioactivity was not readily translocated from leaves or fruit.

Open Access

Abstract

Sweet orange cultivars, Citrus sinensis (L.) Osbeck, in several stages of blight (young tree decline) were studied for characteristics of waterflow or uptake. Many small and major roots and the trunk on moderately blighted trees had restricted waterflow or uptake capabilities. Some small and major roots on the blighted side of early-stage or sectored trees also had restricted waterflow or uptake capabilities, but the healthy side roots functioned similarly to those on healthy trees. Dye uptake patterns confirmed that the waterflow or uptake was restricted in the diseased portions of the trees. On moderately blighted trees, young xylem appeared to be more functional for water movement than older xylem. Necrotic roots were found on the blighted side of early-stage sectored trees and moderately blighted trees, but not on the healthy side of sectored trees or on healthy trees. The sectoring type of early blight expression affords a model system for study whereby both blighted and apparently healthy tissues occur on the same tree.

Open Access