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- Author or Editor: Shaul P. Monselise x
Abstract
Flowering, peel growth and abscission provide examples of processes regulated by endogenous hormonal balance and susceptible of reacting to applied growth substances. Knowledge, accumulated during recent years, of internal balances and of reactions elicited by exogenous factors, has been integrated. Aspects of mode of action, dynamics of processes, the time component, non-hormonal factors and their interaction with internal hormonal balance and applied regulators are discussed in relation to application.
Abstract
The science and practice of growing plants and the study of their usable parts and products are traditionally two separate fields of horticulture. The former is the domain of production physiologists, the latter of postharvest physiologists. Nevertheless, it is common knowledge now that preharvest conditions are of the outmost consequence to the quality of postharvest products. Indeed, in the past 25 years, reports on studies linking preharvest factors and postharvest behavior have become more frequent (3, 5, 20, 28), but we know of a few attempts to survey their interaction in a general way.
Abstract
Electrical conductivity (EC) measurements were carried out in orange (Citrus sinensis (L.) Osbeck) peel (with stainless steel electrodes penetrating 2 mm deep), during fruit growth and subsequent prolonged storage on shelf. Values at the equator were quite generally lower than at the stem and especially at the stylar ends. A curve showing two maxima, one at a very young fruitlet stage (late May) and the other two months before maturation was found. The decrease in EC toward maturation continued for some time postharvest while the water content of tissues decreased, but was followed by an increase with progressive tissue senescence. This last part of the curve is tentatively explained by an increased role of symplast conductance due to tissue aging.
Abstract
Organic acid components of tissues of grapefruit (Citrus paradisi Macf.) were analyzed by gas-liquid chromatography. At harvest, in autumn, malic acid was the main component of the flavedo (78% of total acid content), with malonic, adipic, citric, succinic and oxalic, ranging in order from 11% to 2%. In the albedo, malic was again the prevalent acid (67%), with malonic, adipic, oxalic and succinic acids ranging in order from 19% to 2%; citric acid was present in traces only. In the juice, citric was the prevalent acid (87%), malic attained 12% while other acids were present only in minute amounts. Malic, malonic, adipic and succinic acids in the flavedo declined when the fruit was left on the tree but increased during off-tree storage. Oxalic acid disappeared from the flavedo during storage. Orange and grapefruit acids are compared.
Abstract
Tracheal sap was extracted from stem and root segments of ‘Troyer’ (Poncirus trifoliata × Citrus sinensis), ‘Volkamer’ lemon (C. volkameriana), and sour orange (C. aurantium L.). Thirty to 100 μl of sap were used for determination of amino acids, cytokinins, and gibberellins. Proline, γ-aminobutyric and aspartic acid, arginine, and serine were the main (90–94%) amino acids found in sap of ‘Troyer’ and ‘Volkameriana’. Cytokinin-like activity was higher in orange (C. sinensis Osb.) trees on ‘Volkamer’ lemon than on ‘Troyer’ rootstock. Gibberellin activity in alternate-bearing ‘Wilking’ [‘King’ × ‘Willowleaf’ (C. reticulata Blanco × C. sinensis) × C. reticulata] sap was higher in fruiting shoots late in the on-year than in nonfruiting shoots late in the off-year.
Abstract
The dependence of fruit growth of grapefruit (Citrus paradisi Macf.) upon leaf area was investigated on girdled branches by manipulating leaf and fruit numbers. Leaf areas of 2.0 ± 0.5 m2 per fruit were found to be saturating with regard to fruit growth rate and size. Fruit on internal, shaded branches required larger leaf areas. Fruit on girdled branches weighed 44 to 119% more than fruit in ungirdled branches, which had leaf areas of 0.35 to 0.55 m2 per fruit. This indicates that leaf area is one of the factors limiting fruit growth. Starch accumulated in thin twigs during the fruit growth season, forming a saturation curve similar to those obtained for fruit size when plotted against leaf area per fruit. Increasing leaf area per fruit could involve a decrease in photosynthetic activity, a possibility which now is being investigated further.