Gibberellic acid: translocation, metabolism and effects on peel quality of marsh' grapefruit (Citrus paradisi Macf.)
Ferguson, Louise
Thesis of Ph.D., University of Florida, 1984, 99 pages
1984
บทคัดย่อ
Gibberellic acid maintains 'Marsh' grapefruit peel quality by delaying senescent peel color development and loss of peel firmness. Combined with 2,4-dichlorophenoxyacetic acid (2,4-D), which prevents preharvest fruit drop, the two extend the grapefruit harvest season. It was not known if decreased irrigation affects this treatment. It also was not known if postharvest application of this treatment would produce the same effects. In addition, the parameters of GA(,3) uptake, translocation and beginning metabolism were unknown. This dissertation was undertaken to answer these questions.
'Marsh' grapefruit on rough lemon (Citrus jambhiri Lush.) rootstock received irrigated and unirrigated treatments. Half of each irrigation treatment received a GA(,3) and 2,4-D spray at colorbreak. Preharvest sprays of GA(,3) and 2,4-D extended the grapefruit harvest season by increasing fruit removal and rind puncture force, delaying development of senescent color, and decreasing late-season and postfreeze fruit drop. Although soil moisture content in the top 0.9 m of unirrigated blocks was reduced by approximately 40%, leaf water potentials of these trees and performance of GA(,3) and 2,4-D were unaffected.
Experiments were carried out comparing the effects of a preharvest GA(,3) and 2,4-D spray, a postharvest GA(,3) and 2,4-D dip, and combined spray and dip treatments on peel quality and decay during storage. Fruit harvested in January, March, and May were stored for 12 weeks at 15.5(DEGREES)C. GA(,3) and 2,4-D treated fruit had less senescent color development, loss of puncture strength, and decay than controls. The three treatments were equally effective for January and March harvests, while preharvest and combined treatments were more effective than a postharvest treatment in May.
Applied ('14)C-GA(,3) was absorbed by peels and leaves of attached fruit within 1 hour, translocated in both directions within 4 to 8 hours, and persisted in leaves and peel in measurable amounts for 8 weeks. Accumulation was higher in peels than in leaves no matter where the ('14)C-GA(,3) was applied. Evidence indicates that half of the absorbed ('14)C-GA(,3) remained in the applied form and half was converted to a water-soluble form within 96 hours. Recovery was less, but metabolism was similar, when ('14)C-GA(,3) was applied to detached fruit.