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Abstract

Mesocarp development of peach [Prunus persica (L.) Batsch cv. Redhaven] as measured by fresh weight and size increase, progressed along a double sigmoid curve which was reflected in the activity of extractable wall-associated α- and β-nitrophenylgalactosidases. Enzyme activities, both on protein and dry weight basis, rose rapidly during early fruit development, leveled off, then again rose rapidly at maturation. There was more α-nitrophenylgalactosidase activity than β-nitrophenylgalactosidase activity throughout development. Increases in both galactosidases followed rather than preceded increases in size. The final increases were, however, well correlated with fruit maturation.

Open Access

Abstract

Production rates of CO2 and C2H4 by fruits of jujube (Zizyphus jujuba Lam.), picked at the whitish-green stage and held at 20°C for 15 days, followed a nonclimacteric pattern. Skin color changed from whitish-green to reddish-brown with fruit maturation. Relative to most other fresh fruits, Chinese jujubes are lower in water content and titratable acidity, and higher in total sugars (mostly reducing sugars) and phenolics. Chinese jujubes are very rich in ascorbic acid (Vitamin C) content which increased with maturation to 559 mg/100 g fresh weight. Fruits held at 0° for 26 days exhibited sheet pitting due to chilling injury.

Open Access

Although somatic embryogenesis in vitro has been carried out successfully in a number of plants, a limiting factor in many somatic embryogenic systems is that plantlet regeneration is not obtainable or restricted to low frequencies. We have developed a repetitive, high frequency somatic embryogenic system in pecan (Carya illinoensis) and have identified effective treatments for improved somatic embryo conversion. A 6 to 10 week cold treatment followed by a 5 day desiccation, promoted enhanced root germination and extension, and epicotyl elongation. Light and transmission electron microscopic evaluations of somatic embryo cotyledon development will be presented and related to conversion enhancing treatments and their possible roles in embryo maturation.

Free access

Although somatic embryogenesis in vitro has been carried out successfully in a number of plants, a limiting factor in many somatic embryogenic systems is that plantlet regeneration is not obtainable or restricted to low frequencies. We have developed a repetitive, high frequency somatic embryogenic system in pecan (Carya illinoensis) and have identified effective treatments for improved somatic embryo conversion. A 6 to 10 week cold treatment followed by a 5 day desiccation, promoted enhanced root germination and extension, and epicotyl elongation. Light and transmission electron microscopic evaluations of somatic embryo cotyledon development will be presented and related to conversion enhancing treatments and their possible roles in embryo maturation.

Free access

Rootstock influence on bloom date and fruit maturation of `Redhaven' peach [Prunus persica (L.) Batsch] was studied over a 3-year period. Rootstock included seedlings (Lovell, Halford, Bailey, and Siberian C) and cuttings (GF677, GF655.2, Damas 1869, and `Redhaven'). Bloom dates of the various combinations differed in all 3 years, with a range of 3.6, 9.1, and 7.3 days in 1988, 1989, and 1990, respectively. Fruit development period differed each year with a range of 3.9, 5.8, and 4.4 days in 1988, 1989, and 1990, respectively. `Weighted-average harvest date also differed with a range of 3.6,2.9, and 5.6 days in 1988, 1989, and 1990, respectively. `Redhaven'/Lovell was the latest blooming and maturing combination in all 3 years of the study.

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Plant regeneration from tissue cultures of summer squash (Cucurbita pepo L. ev. YC60) has been observed. Embryogenic callus tissues were initiated when cotyledons of mature seeds were excised and cultured on Murashige and Skoog (MS) medium supplemented with either 22.7 μm 2,4-D or a combination of 4.7 μm 2,4,5-T, 4 μm BA, and 0.5 μm kinetin. Clusters of somatic embryos were found in callus tissue. Maturation of these somatic embryos was effected by transfer of embryogenic callus tissues to MS supplemented with 0.5 μm NAA and 0.25 μm kinetin. Regenerated mature plants were morphologically normal and set fruits containing seeds that germinated normally. Chemical names used: 6-benzylaminopurine (BA); 2,4-dichlorophenoxyacetic acid (2,4-D); α - napthaleneacetic acid (NAA); 2,4,5-trichlorophenoxyacetic acid (2,4,5-T).

Free access

New Mexican chile peppers were harvested at weekly intervals beginning 105 days after planting (DAP), and evaluated for ethylene (C2H4) production, respiration rates, chlorophyll content, beta-galactosidase activity, polygalacturonase (PG) activity, and fruit firmness. Physiological changes were most apparent in peppers harvested 139-154 DAP. Beta-galactosidase activity increased rapidly beginning 147 DAP, and reached a peak of 24.5 mmol·gfw-1 when peppers were harvested 160 DAP. Polygalacturonase was not detectable at any stage of maturation. Fruit firmness was greatest (35.8 N) at 139 DAP and decreased significantly at 160 DAP. Carbon dioxide production and chlorophyll content were highest in young pods harvested 105 DAP, and decreased steadily thereafter. Ethylene production peaked (0.185-0.202 nl·gfw-1·h-1) in peppers harvested between 146-154 DAP.

Free access

Repeated preharvest applications of methyl jasmonate (MJ) to 'Fuji' apple [Malus sylvestris var. domestica (Borkh.) Mansf.] fruit were evaluated for impacts on peel color, size, fruit finish, and maturation. MJ treatments at 2 week intervals began 48 days after full bloom (DAFB) (early season) or 119 DAFB (late season) and fruit were harvested 172 DAFB. MJ treatment stimulated significant increases in peel red color following the initial application and thereafter. Early season MJ treatment reduced fruit diameter and length to diameter ratio but slowed softening and starch hydrolysis. Fruit receiving late season MJ treatments had increased incidence of bitter pit and splitting, shorter green life, and slower softening. Results suggest preharvest application of MJ impacts apple color development and other aspects of fruit quality. Chemical name used: methyl 3-oxo-2-(2-pentenyl)cyclopentane-1-acetate (methyl jasmonate).

Free access

Abstract

Fruit samples of grape (Vitis labrusca L., cv. Concord) from 6 vineyard locations were collected at 7 to 10-day intervals beginning prior to veraison and continuing through development of 16% soluble solids for a period of 19 years. The 19-year average date for peak bloom in these vineyards was May 19, for 8% soluble solids development was July 27 (69 days from peak bloom), and for 16% soluble solids development was August 23 (96 days from peak bloom). Heat unit summations were more closely related to development of soluble solids than to changes in either titratable acidity or color. Using degree-day accumulations and effective heat unit summations did not prove to be methods superior to use of the number of calendar days for predicting grape maturation. Predictions from 8 to 16% soluble solids development were more accurate than predicting from peak bloom (when 50% of clusters showed bloom). Variations between years and between vineyard locations within a given year prevented accurate predictions from the 3 methods. Other deterrents observed in predicting development of soluble solids included the cultural variables of fruit load and soil moisture.

Open Access

Abstract

Temperatures for several post-bloom periods were correlated with days from full bloom to ‘Bartlett’ pear maturity. Date of maturity based on pressure test showed a high negative correlation (r = -.88) with mean temp above 40°F for the 36 days following bloom. The peak thermal period occurred 26-30 days after bloom, with the highest correlation on the 28th day. Days to maturity had a higher correlation with accumulated mean temp above 45°F than with degree hr above 45°F for the same periods. Base temp of 38.5°F to 50°F gave r values greater than -.85 in this prediction method. Mean temp between 41.5°F and 68.5°F on the 28th day had a linear correlation r of -.71 with days to maturity. Equal temp increments were more effective at min levels than at max levels for accelerating maturity. The post-bloom thermal period affecting maturation coincides with the stage of cell division and most effective time for application of chemical thinning sprays.

Open Access