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  • Author or Editor: Janice C. Morrison x
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Grape berries (Vitis vinifera L., `Thompson Seedless') exuded a variety of compounds through the cuticle and epicuticular wax layer onto the berry surface. The composition of the exudate changed through the course of the growing season. Phenolic compounds and malic acid were in relatively high concentrations in grape berry exudates after bloom, but were low in exudates from mature fruit. The rate of decrease of phenols and malic acid was more rapid during the early stage of berry growth than during the ripening period. Sugar and potassium concentrations in the berry exudates were low at bloom, but increased rapidly in the later stages of ripening. Water extracts of berry exudates contained sugars, malic acid, potassium, and sodium. The water extracts promoted mycelial growth of Botrytis cinerea Pers. Ethanol and ether extracts contained phenols and lipids. These fractions from fruit sampled in the first 3 weeks after bloom strongly inhibited mycelial growth. The inhibitory effect of these fractions decreased later in the season.

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Abstract

Intact almond fruits [Prunus dulcis (Mill.) D.A. Webb.] showed a transient increase in ethylene production at the time of gum duct initiation. Treatment with ethylene promoted gum duct formation if applied 1 week before natural duct initiation, but had no effect when applied earlier. Silver thiosulfate, applied either as a spray or through bark-feeding, was found to delay natural duct initiation. AO A also delayed duct initiation when applied through bark-feeding, but not when applied as a spray. Chemical name used: aminooxyacetic acid (AOA).

Open Access

Abstract

Cell wall-degrading enzymes were extracted from the cell wall free space of mesocarp tissue from immature almonds [Prunus dulcis(Mill.)D.A. Webb, ‘Nonpareil’]. The activities of several of these enzymes were found to correlate with the development of gum ducts in this tissue. Polygalacturonase (EC 3.2.1.15) and 1,3-β-D-glucanase (EC 3.2.1.39) activities rose sharply at, or just prior to, the early schizogenous stage of duct initiation, while increases in α-galactosidase (EC 3.2.1.22), β-galactosidase (EC 3.2.1.23), α-arabinosidase (EC 3.2.1.55), and α-mannosidase (EC 3.2.1.24) activities were correlated with the later lysigenous stage of duct formation. Cell wall analysis of almond mesocarp tissue sampled the week preceding gum duct formation determined that the predominant noncellulosic sugars present in the mesocarp cell walls are arabinose, galactose, xylose, and glucose, with smaller amounts of rhamnose and mannose also present. The walls also contain a high percentage of galacturonic acid and trace amounts of glucuronic acid. Methylation analysis of the cell walls confirmed that many of the specific glycosidic linkages that are cleaved by the enzymes tested are present in the mesocarp cell walls immediately prior to gum duct formation.

Open Access