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Abstract
‘Redblush’ grapefruit seedlings, with and without leaves, were sprayed 1 to 5 times with 100 to 1000 ppm abscisic acid or 500 to 3000 ppm cycocel. Plants were subsequently exposed to several day/night temperature regimes which included 70°/50°, 90°/70°, and 95°/95°F. Both abscisic acid and cycocel delayed bud growth of leafy and defoliated seedlings. Abscisic acid was more effective than cycocel, and both compounds were most effective in delaying bud growth at lower temperatures, higher concentrations, and with more than one application. Abscisic acid was more toxic than cycocel, and both compounds were more toxic to defoliated plants than to leafy plants. Gibberellic acid overcame a correlative bud inhibition by the leaves, and abscisic acid decreased the effect of gibberellic acid.
Abstract
Four abscission materials were evaluated to determine their effects on ethylene production and abscission of fruit and leaves of orange (Citrus sinensis (L.) Osbeck cvs. Hamlin and Valencia): 5-chloro-3-methyl-4-nitro-1H-pyrazole (Release) glyoxal dioxime (Pik-Off), cycloheximide (3-[2-(3,5-dimethyl-2-oxocyclohexyl-2-hydroxyethyl]-glutarimide or Acti-Aid) and cycloheximide in combination with chlorothalonil (DS-27914). All chemicals enhanced internal fruit ethylene levels and subsequent fruit loosening. However, the magnitude and timing of the fruit ethylene response varied with each chemical and correlated with fruit loosening and subsequent retightening. The pattern of ethylene production may indicate the optimum fruit harvest period and the degree of leaf abscission for each chemical.
Abstract
2-Chloroethylphosphonic acid (Ethrel) applied at 50 to 200 ppm as a preharvest spray, showed considerable promise in degreening ‘Robinson’ and ‘Lee’ tangerine fruit. The preharvest degreening resulted in less postharvest degreening time required for acceptable color and less fruit decay during storage. Ethrel concn between 100 and 200 ppm caused abscission of some old leaves, but had no apparent effect on external appearance other than color.
Abstract
We collected lemon leaves from 25 trees growing in control and artificially salinized plots at Indio, California, 4 and 6 weeks after beginning of irrigation with water carrying 5,000 ppm total salt. Chloride content of the leaves was directly correlated with their ethylene production. Leaves with visible injury from high Cl produced more ethylene than those with no visible injury from salinized plots; foliage from the latter treatment produced more ethylene than those from nonsaline control plots. The correlation coefficient was significant at odds of 19:1 at 4 weeks and 99:1 at 6 weeks.
Abstract
Comparisons were made of the composition of ‘Valencia’ oranges, Citrus sinensis Osbeck, from orchards in 6 major climatic zones used for citrus culture in the U. S. Six orchards, selected in a compact area in each location, were measured and sampled at intervals during 2 crop seasons. The locations were: Orlando, Fla.; Weslaco, Tex.; Tempe, Ariz.; Indio, Calif.; Riverside, Calif.; Santa Paula, Calif. Statistical evaluations showed that the seasonal trends for most measurements differed significantly among locations.
Observations on flowering showed that full-bloom occurred from 1 to 2 months later in the Far-Western locations than in Texas and Florida. The extremes of the interval between an thesis and the beginning of ripening (a 9 to 1 ratio of total soluble solids to acid in juice) varied from 71/2 to 81/2 months in Weslaco, to 14 to 15 months in Santa Paula, but earliness or lateness of maturity could not be relatd in any simple, obvious manner to the characteristic of the seasonal temperature regimes in the 6 locations. In general, rinds were thinner, smoother and slower to color, and fruits larger, and juicier in Orlando and Weslaco than in the Far-Western locations. Total soluble solids and ascorbic acid in juice at comparable stages of maturity were not influenced in a predictable manner by location, although significant differences occurred in a given season. Of the juice constituents, the acids appear to be the most consistently influenced by climatic conditions during the rapid growth and maturation periods of fruit development. The warmer the climate, the more rapid was the rate of decrease of total acid concentration. Seediness of fruit was influenced by both location and season. Measurements of comparable samples of fruit obtained from widely divergent climatic parameters suggest that the numerous growth and metabolic processes involved in ripening of citrus fruits have independent internal controlling mechanisms. Apparently these processes interact in different ways with external environmental factors, and are not dominated by a pervasive, common internal maturity factor.