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  • Author or Editor: S. J. Kays x
  • Journal of the American Society for Horticultural Science x
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Abstract

The O2 and CO2 concentration between the shuck and shell and within the nut of individual pecans (Carya illinoensis (Wang.) K. Koch cv. Stuart) was monitored over a 4 week period from predehiscence to post-dehiscence. Internal O2 levels increased after dehiscence from initial concentrations of 16-17% to near that of the external environment after 3 weeks. Internal CO2 concentration, conversely, decreased substantially after dehiscence. Treatment of nuts over the same physiological stages of development with 2.5, 5.0, 10.0, 21.0 and 100% O2 had little effect on the induction and development of the kernel's normal pigmentation. Both high and low O2 levels did, however, produce some discoloration after 21 days of treatment. Changes in the internal nut O2 partial pressure are apparently not a significant factor in the induction and development of the normal complement of pecan kernel pigments during fruit maturation.

Open Access
Authors: and

Breeding sweetpotatoes [Ipomoea batatas (L.) Lam.] for improved flavor would be greatly facilitated by understanding the flavor chemistry of the crop. To ascertain the chemical composition of the aroma, an aroma extract of baked `Jewel' sweetpotatoes was obtained using a cold solvent trap system and analyzed by gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS) and gas chromatography olfactometry (GCO) using aroma extract dilution analysis (AEDA). GC with a flame ionization detector (GC-FID) revealed ≈60 compounds presented in the aroma extract, of which 48 were identified. Olfactory evaluation of the eluted compounds using GC with a thermal conductivity detector (GC-TCD) indicated the presence of 37 odor-active peaks in the aroma extract. Three compounds, phenylacetaldehyde (perfume), maltol (caramel), and methyl geranate (2,6-octadienoic acid, 3,7-dimethyl-, methyl ester) (sweet candy) possessed the highest flavor dilution (FD) values (1500) via AEDA. 2-Acetyl furan (baked potato), 2-pentyl furan (floral), 2-acetyl pyrrole (sweet, caramel), geraniol (sweet floral), and β-ionone (violet) had FD values of 1000. These compounds are thought to be the most potent odorants in baked `Jewel' sweetpotatoes. Additionally, 1,2,4-trimethyl benzene, 2-furmethanol, benzaldehyde, 5-methyl-2-furfural, linalool, isopulegone, n-decanal, 2,4-decadienal, octyl ketone, α-copaene, 4-decanolide, and one unidentified compound were also contributors to the aroma. There was not a character impact compound that comprised the basic baked sweetpotato aroma. The aroma appeared to be made up of a relatively complex mixture of compounds. Maillard and/or caramelization reactions, Strecker degradation of phenylalanine, lipid and carotenoid degradation, and the thermal release of glycosidically bound terpenes appear to be involved in the formation of the characteristic aroma of baked `Jewel' sweetpotatoes.

Free access
Authors: and

Abstract

Respiration of sweet potato roots was significantly depressed by low oxygen concentrations from 5 to 15% compared to 20% O2, but respiration at 2.5% O2 was high. Total sugar accumulated with low oxygen (2.5 and 5.0%) storage. Protopectin was low in roots stored at low O2 concentrations but water soluble pectin was not significantly affected. Physical parameters Ew and δf the storage roots were high when stored at low O2 concentrations. Ey and Ef were not significantly affected. Ew was correlated with total sugar (r = 0.79).

Open Access
Authors: and

Abstract

Several environmental and physical factors affect the kinetics of ethylene release from (2-chloroethyDphosphonic acid and (2-chloroethyl)methylbis(phenylmethoxy)silane. Target surface chemistry exerted a strong influence on the evolution of ethylene from both compounds. Ethylene release from (2-chloroethyl)methylbis(phenylmethoxy) silane was slowed by glass and hydrophobic substances such as wax, surfactants in the spray solution, and high concentrations of the parent molecule, but not by epicuticular waxes on leaves. Ethylene evolution from (2-chloroethyl)phosphonic acid was inhibited by glass and high levels of epicuticular waxes. The rate of ethylene release from both compounds was positively correlated with temperature; however, ethylene released from (2-chloroethyl)methylbis(phenylmethoxy)silane was much less affected by temperature increases. Increases in light intensity promoted the initial release of ethylene from (2-chloroethyl)methylbis(phenylmethoxy)silane, but decreased long-term yield. Light intensity had no effect on the breakdown of (2-chloroethyl)phosphonic acid.

Open Access
Authors: and

Abstract

Patterns of deposition of [14C]-photosynthate in the storage roots of Ipomoea batatas (L.) Lam. at 3 stages of development (44, 74, 105 days from planting) were distinct for each labeling period. [14C] initially accumulates in the vascular cambial region after labeling (24 hours); however, all areas of the storage root show discernable activity. Label in this region is lost with time probably through cell division with the majority of the label ending up in bundle parenchyma. Deposition of [14C]-photosynthate appears to occur for more than 24 hours reflecting either continued transport from aerial portions of the plant or redistribution within the root. Roots labeled early in their development do not have a uniform distribution of [14C] in the central stele, possibly due to later development of anomalous cambium. [14C] in the cortical region does not appear to be redistributed inward during subsequent growth of the root. [14C] deposited early in the development of the storage root was concentrated at the distal end with longitudinal bulking proceeding toward the proximal end. Invaginations along the surface of the root giving a furrowed appearance appear to be due to differential rates of activity of the vascular cambium in those regions.

Open Access
Authors: and

Abstract

Substantial quantitative differences in kernel pigmentation of pecan (Carya illinoensis (Wang) K. Koch) were measured in 8 cultivars and 1 selection. These pecans exhibit a wide range in color stability with storage and reversibility of detrimental color changes using surface pH alteration. Major differences were found between genotypes in the positive benefit from storage in the unshelled versus the shelled state.

Open Access
Authors: and

Abstract

Plant populations of tomato (12.7 × 12.7, 25.4 × 25.4 and 50.8 × 50.8 cm) were studied from the standpoint of changing water needs, alterations in the composition of the soil gas phase, and changes in soil compaction. Increased populations of plants required progressively more water per unit area of land. Distinct changes in the soil gas phase also occurred with increased plant population, date of measurement, and depth in the soil. A typical inverse relationship between CO2 and O2 concentration occurred with increasing soil depth. Both CO2 and O2 decreased with increased population. An inverse relationship between CO2 and O2 occurred in the early part of the growing season, while a positive correlation was noted in the latter part. The O2 concentration increased progressively during the growing season. The concentration of ethylene in the soil gas phase increased during the growing season, however, no significant population or depth effects were noted. There were no significant differences in soil compaction with increased plant population; however, a progressive consolidation with time occurred. Increases in population density of tomatoes resulted in both changes in requirements for production and distinct alterations in the plant community’s environment.

Open Access

Abstract

[14C-ethyl] labeled (2-chloroethyl)methylbis(phenylmethoxy)silane (CGA-15281) was applied to fruit and leaves of 4-year-old ‘Bicentennial’ peach trees [Prunus persica (L.) Batsch]. Virtually none of the parent material moved into the fruit or was taken up and transported in vegetative tissue. Of the small amount found within the vegetative tissue, there was equal distribution between acropetal and basipetal movement. The compound appears to act through the release of ethylene which penetrates the tissue rather than uptake of the parent molecule and subsequent release.

Open Access

Abstract

The effect of time of harvest prior to complete field drying of 2 cultivars of dry bean (Phaseolus vulgaris L.) was analyzed relative to the quality of the processed product produced. Early harvest did not significantly affect yield (at 10% raw product moisture); however, it did have a significant effect on the quality of the processed product. Typically the processed dark red kidney and pinto beans were more intensely pigmented with later harvest dates, were firmer, and had fewer split seeds. The respiratory rate of the raw product was highly correlated (r = 0.993) with the raw product moisture level. Only small differences were found in the degree of pigmentation of the processed product when comparing the spring with the fall crop of pinto beans. The fall crop of pinto beans had a substantially lower incidence of split beans in the canned product.

Open Access

Abstract

Pepper transplants (Capsicum annuum L.) held under simulated transit conditions synthesized substantial amounts of ethylene, the rate of which was temperature dependent. Transplants treated with known concentrations of ethylene (0, 0.1 to 10.0 μ1/liter) were substantially defoliated at levels lower than those that may be produced in transit by the plants themselves. Exposure to ethylene concentrations of 0.5 jul/liter and greater impeded the growth of transplants after planting into the field. Removal of ethylene in storage with potassium permanganate greatly reduced abscission. Elevated storage CO2 levels stimulated ethylene synthesis by as much as 34%.

Open Access