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  • Author or Editor: T. R. Kemp x
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Abstract

Plants and detached fruits of mature green bell peppers (Capsicum annuum L. cv. Yolo Wonder B.) were treated with (2-chloroethyl)phosphonic acid (ethephon) and 2-(4-chlorophenylthio)triethylamine hydrochloride (CPTA) to enhance red color development. Ethephon sprayed on plants in the field greatly enhanced red color development in fruits in 1971. However, in 1972 when temperatures were cooler after spray treatments than in 1971, neither ethephon nor CPTA affected fruit color even though plants showed the effects of chemical treatment by turning slightly chlorotic. Furthermore, dipping detached fruits in ethephon had no effect, but fruits dipped in CPTA turned yellow instead of the usual red color.

Open Access

Two methods for collecting headspace vapors produced by plant samples are presented. The first involves entraining volatiles in a stream of air and trapping the entrained compounds on a porous polymer such as Tenax. The volatiles are recovered from the trap by solvent extraction or heat desorption and analysed by gas chromatography. A second method entails removing headspace vapor above plant material with a gas-tight syringe and injecting the sample directly into the gas chromatograph. An evaluation of the usefulness of these techniques will be presented.

Free access

Abstract

One-year-old Mailing (M) 26 and Mailing Merton (MM) 111 apple rootstocks (Malus sp) were planted in pots in a greenhouse in March and harvested monthly from May to October. Samples of the shoot tip, stem bark, and new and old roots were collected for PVP-bonded and simple phenol analyses. The PVP-bonded phenols were highest in the shoot tip and lowest in the old roots. There was no consistent relationship with rootstock or time of collection. Five phenols were found in the shoot tip, 8 in the bark, and 8 in the new roots, including protocatechuic, ferulic, and benzoic acids. Benzoic acid was found only in the new roots. Phloridzin composed more than 90% of all the simple phenols found and was higher in MM 111 than in M 26 rootstock. The other phenols were not consistently higher in either rootstock and had few trends with time of collection. No direct relationship was found between phenol levels and dwarfing characteristics.

Open Access

Abstract

Cytokinins were extracted from whole root tissue of aeroponically cultured Chrysanthemum morifolium Ramat., purified by cation exchange, paper and Sephadex LH-20 column chromatography and bioassayed with tobacco callus. Compounds with chromatographic properties similar to those of zeatin and zeatin riboside were found to be the major cytokinin components of the roots.

Open Access

Abstract

Excised flower buds of Nicotiana affinis were grown to maturity in media in which growth regulators were added to evaluate their effects on growth and development. As the concentration of naphthaleneacetic acid (NAA) was increased from 10-7 to 10-4 m, the number of days required for the buds to open decreased, and the number of days required for the corolla tubes to turn brown increased. Indoleacetic acid (IAA) and indolebutyric acid (IBA) did not affect the rate of bud opening. As the concentration of IBA was increased, however, the days required for the corolla tubes to turn brown increased, but not as much as for buds in media with NAA. IAA had no effect on browning of corolla tubes. At high concentrations of NAA and kinetin the corolla tubes were shortened. Kinetin did not affect the rate of bud opening or days till the corolla tubes turned brown.

Open Access

Abstract

Cytokinin activity was indicated in roots of Chrysanthemum morifolium Ramat, cv. Polaris cultured using a nutrient film technique and assayed at 3 stages of plant development: young, actively growing; mature flowering; and senescing with dried flowers.

Open Access

Prior work indicated that volatile compounds produced by macerated strawberry fruit occurred at levels capable of affecting pathogen development. To determine if a less-severe injury, such as bruising, would alter the volatile profile of strawberry fruit, the headspace volatiles from ripe `Tribute' strawberry fruit were sampled with SPME fiber during the 15 min immediately following and from 75 to 90 min following application of a compression bruise. The compression bruise was applied with a force gauge, and fruit were kept in a closed bottle at room temperature during the study. Of the 14 major volatile products consistently produced by all fruit, acetate esters derived from hexanal, (E)-2-hexenal, and (Z)-3-hexenal increased most, over 50%, in response to bruising during the first interval. During the later interval, bruised fruit produced over 50% more (E)-2-hexenyl acetate and hexyl acetate than control fruit. Most notably, the ratio of levels of (E)-2-hexenyl acetate produced by bruised compared to control fruit were the highest among all 14 major volatiles, over 150% more after 15 min and 270% more at 90 min. Headspace levels of the 6-carbon acetate esters declined for both control and bruised fruit between 15 and 90 min, while levels of the other major volatiles increased. The other 11 volatile compounds were commonly identified aroma volatiles. Headspace levels of some of these were also higher from bruised than control fruit. In particular, headspace levels of ethyl butyrate were increased by bruising 13% after 15 min but over 100% after 90 min, the most of any volatile product other than (E)-2-hexenyl acetate.

Free access

Strawberry fruit were inoculated with the human pathogen E. coli O157:H7, and the bacteria were recovered from the fruit over a 3-day period of storage at room temperature. The bacterial population was maintained on fruit when the inoculation level was relatively high and increased when the inoculation level was low. The volatile metabolites of E. coli O157:H7 growing on plate count agar (PCA) and on inoculated strawberry fruit were collected by a headspace trapping system and analyzed by gas chromatography and GC-mass spectrometry. E. coli O157:H7 grown on PCA produced a variety of volatile compounds including indole as a major component and a series of methyl ketones. A nonpathogenic E. coli also produced these compounds. However, there was not an appreciable amount of indole collected from E. coli O157:H7 inoculated strawberry fruit as compared to the large amount of volatiles produced by the fruit. Strawberry fruit were able to capture over 95% of the vapor phase indole fed to them from a neat source.

Free access

A number of natural volatile compounds exhibit promise as postharvest fumigants for control of Botrytis on strawberry fruit. Because some of compounds may cause apparent phytotoxic responses by the fruit, short duration treatment is desirable. The compounds have been evaluated in single fruit bioassays with passively established modified atmospheres using a polymer film. The compound source was removed after 3 hours, 1, 3, or 7 days, or remained in the containers for the 10 day duration of the study. At levels which inhibited Botrytis in closed containers without film, E-2-hexenal was effective with a 1-day treatment, diethyl acetal was increasingly effective as treatment period increased, and 2-nonanone and methyl salicylate were not effective with continuous treatment. The levels of both the source compound and its metabolites were different using the film than without it. The film, used to allow gas diffusion and exchange with the surrounding environment, may allow diffusion of the volatile compounds and their metabolites. Thus, successful use of the compounds in modified atmosphere storage may require knowledge of their diffusion through the films to establish the appropriate levels for effective fumigation of the fruit and avoid adverse quality effects.

Free access