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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.
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.
Abstract
Changes in the levels of putative free and conjugated indole-3-acetic acid (IAA) were examined by high performance liquid chromatography (HPLC) during the first 96 hr of adventitious root formation in mung bean [Vigna radiata (L.) R. Wilcz. ‘Berken’] stem cuttings. The putative IAA was characterized as biologically and chemically similar to IAA; ester- and amide-conjugated IAA also were found. Amide-conjugated IAA was an order of magnitude more abundant than either free or ester-conjugated IAA, both of which were present at low levels. In duplicate experiments, the relative levels of free and conjugated IAA in the rooting region fluctuated similarly during root formation, although some differences in timing and magnitude were observed.
Volatile compounds, commonly produced by flowers during bloom, have been described as insect attractants. Some of these compounds stimulate Pinus pollen germination in vitro (French et al., 1979, J. Agric. Fd. Chem., 27184-187), suggesting that such compounds may do the same in vivo. Red Delicious apple pollen was germinated on agar in a simple, enclosed in vitro bioassay system in the presence of a number of plant tissues, including apple, tomato, and chrysanthemum leaves, apple flowers, rose petals, and apple fruit slices. These tissues represent a diversity of types of volatile compounds, Pollen germination was recorded by microphotography after 1 and 2 hours, and percent germination was determined. Although stimulation of germination was not observed, macerated tomato leaves inhibited it. To determine if the volatile characteristics of cultivars differ, flowers of Red Delicious and Golden Delicious apple were harvested at full bloom. Their volatiles were collected, identified, and quantitated by capillary GC-MS. Among 8 major compounds common in the two cultivars, several quantitative differences were observed. These results will be discussed in relation to the potential role of volatiles in pollen germination.
Carolina Bunch is a sweetpotato cultivar that combines high yield, excellent flavor and appearance with multiple pathogen and pest resistances. It is ideal for home or market gardens, because of its short vine and bunch habit that allow for production of high yields in a limited space. The roots are fusiform with uniform shape and a smooth, bright, light copper skin and dark orange flesh. When baked, the roots have a smooth texture and are sweet, moist and have excellent flavor and appearance. This sweetpotato can be grown virtually without pesticides. It has very high levels of resistances to southern root knot and other species of nematodes, Fusarium wilt, feathery mottle virus, sclerotial blight in plant beds, and Streptomyces soil rot. It has good resistance to many soil insects including several species of wireworm, Diabrotica, Systena, and flea beetles. In the southern US, it yields better than `Jewel' in a growing season of 110-120 days. Foundation roots are available in limited quantities from South Carolina Foundation Seed Association, Inc, 1162 Cherry Hill Rd, Clemson SC 29634-0393.