Simple Method for Continuous Treatment of Plant Material with Metered Traces of Ethylene or Other Gases

The effects of a series of concentrations of ethylene (10, 20, 40, to 10,240 nl,'i) on elongation, diameter, and geotropism of the stems and roots of etiolated seedlings of Pisuin sativum L., Arachis hypogea L., Phaseolus vulgaris L., and Gossypiurn hirsutum L. were measured or observed. Of the 24 possible responses, 4 were unaffected at the concentrations used, 5 were affected slightly, and the remaining responses exhibited a 14-fold range of apparent half-maximum concentration dependencies (i.e. 95 nl/l for the effect on pea epicotyl geotropism to 1350 nl/l for the promotion of cotton hypocotyl diameter MATERIALS AND METHODSIt has been reported that a number of different effects of ethylene have similar concentration dependencies and thus possibly the same primary binding site (2, 4). Further, they observed that a known metal binder, carbon monoxide, replaces ethylene in all its actions at a concentration of several hundred nl/ 1, and that competition between CO2 and ethylene has been established for essentially all actions of ethylene. From these observations it has been suggested that the primary binding site for ethylene action in plants is a metal-containing receptor having a limited access of approach with a Km of 6 X 10'" M (2, 4).There is sufficient published evidence to raise questions about the universality of these conclusions, especially regarding the single concentration dependency. It was noted by the earliest workers that different plant species varied in their sensitivity to ethylene (6,7,11,12 Seeds of peas (Pislim sativumn L., cv. Alaska) and beans (Phaseolus vulgaris L., cv. Burpee's Stringless Green Pod) were imbibed for 6 hr in aerated distilled H20 at 25 C, and seeds of peanuts (Arachis hypogea L., Spanish type, cv. Starr) and cotton (Gossypium hirsutum L., cv. Stoneville 213) were similarly imbibed for 1 hr. The seeds were then placed between moistened layers of white paper toweling which were sandwiched between layers of 1.25-cm thick, open celled urethane foam which had been washed thoroughly with distilled HP and had been drained. A set of seven such layers (with 15 seeds/layer) was held upright in a 30 cm x 10 cm X 25 cm black, opaque plastic container, which was placed in a dark germination cabinet at 25 C. Each container of seeds was supplied with a flow of 8 1/hr of humidified air which had been passed through a 60 cm X 6 cm diameter column of vermiculite and celite (4: 1 v/v) moistened with a saturated solution of potassium permanganate to remove all traces (<2.0 nl/l) of unsaturated hydrocarbons.After a specified number of days the seedlings were transferred to the treatment chambers. The chambers consisted of two 30.5 x 45.7 cm sheets of glass separated by a 1.25-cm thick rubber gasket (which was glued just inside the perimeter of the back sheet of glass). The back sheet of glass was attached to a plywood backing and the front sheet was held in place by a frame which was bolted to the plywood back.

Section: Resultsmentioning

confidence: 90%

Section: Methodsmentioning

confidence: 99%

Concentration Dependencies of Some Effects of Ethylene on Etiolated Pea, Peanut, Bean, and Cotton Seedlings

Goeschl

Kays²

1975

“…Apples were placed in 2 1-L desiccators and ventilated with a constant flow of moist air (32 L h-') containing different concentrations of ethylene and CO2. Ethylene was premixed in cylinders with nitrogen and the desir$d concentrations were diluted into the air stream by means of a barostat and glass capillaries (22). CO2 without premixing with N2, was diluted into the air stream by the same method.…”

Section: Methodsmentioning

confidence: 99%

Ethylene-Promoted Conversion of 1-Aminocyclopropane-1-Carboxylic Acid to Ethylene in Peel of Apple at Various Stages of Fruit Development

Bufler¹

1986

118

Internal ethylene concentration, ability to convert 1-amino-cyclopropane-l-carboxylic acid (ACC) to ethylene (ethylene-forming enzyme IEFEI activity) and ACC content in the peel of apples (Malus domestica Borkh., cv Golden Delicious) increased only slightly during fruit maturation on the tree. Treatment of immature apples with 100 microliters ethylene per liter for 24 hours increased EFE activity in the peel tissue, but did not induce an increase in ethylene production. This ability of apple peel tissue to respond to ethylene with elevated EFE activity increased exponentially during maturation on the tree. After harvest of mature preclimacteric apples previously treated with aminoethoxyvinylglycine, 0.05 microliter per liter ethylene did not immediately cause a rapid increase of development in EFE activity in peel tissue. However, 0.5 microliter per liter ethylene and higher concentrations did. The ethylene concentration for half-maximal promotion of EFE development was estimated to be approximately 0.9 microliter per liter. CO2 partially inhibited the rapid increase of ethylene-promoted development of EFE activity. It is suggested that ethylene-promoted CO2 production is involved in the regulation of autocatalytic ethylene production in apples.

“…The 20 explants rested on a gauze pad placed in the bottom of each chamber. The glass tubing at the top of the chamber was attached to a humidified air flow system (0.35 ml/min) similar to that described by Pratt et al (42). Controls consisted of 1.5-cm explants acropetal to and basipetal to the abscission zone explant (Fig.…”

Section: Methodsmentioning

confidence: 99%

Endogenous Ethylene and Abscisic Acid Relative to Phytogerontology

Swanson¹,

Wilkins²,

Weiser³

et al. 1975

Endogenous production of ethylene and endogenous levels of abscisic acid were measured from Hibiscus rosa-si nensis L. abscission zone explants at six stages of development: tight bud, open flower, closed flower, petal abscission, calyx abscission, and peduncle abscission.Explants acropetal and basipetal to the abscission zone produced less ethylene than the abscission zone explants. Ethylene production increased with time both prior to and during abscission, reaching a peak in the later stages of senescence after abscission was complete.Bound abscisic acid was greatest in segments acropetal to the abscission zone at the closed flower stage. Free abscisic acid was double that of bound abscisic acid in the tight bud stage with the basipetal level exceeding that of the acropetal level until flower closure. Acropetal-free abscisic acid began to rise at petal abscission increasing sharply to a peak at calyx abscission. both. However, ABA has exhibited ethylene production in pea seedlings and stimulated its production in orange peel (24). Ethylene has also been shown to enhance the effect of ABA (50). Some interactions have been observed between ethylene and other growth regulators (1,10,11,23,32,39,47,50). An investigation of endogenous levels of ABA relative to endogenous ethylene production is in order. The objective of this study was to characterize the endogenous levels of ethylene and ABA in Hibiscius rosa-sinensis L. abscission zones to determine possible cause and effect relationships during floral development. MATERIALS AND METHODSHibiscuts rosa-sinienisis L. flower stem explants were used because the abscission zone is accessible and senescence and abscission are rapid. Ethylene and ABA determinations were made from abscission zone No. 2 (Fig. 1) (Fig. 2), as defined according to the development, senescence, and abscission of the flower petals, calyx, and peduncle. Explants 1.5 cm long, with the abscission zone centered. were used for ethylene analysis (Fig. la). Explants were surface-sterilized in 0.5% sodium hypochlorite for 4 min, blotted dry, and aseptically transferred to sterile flow chambers.The flow chamber consisted of a 7 cm X 1.5 cm (i.d.) glass tube fitted at each end with a 5 cm X 4 mm (i.d.) glass tubing in a rubber stopper. The 20 explants rested on a gauze pad placed in the bottom of each chamber. The glass tubing at the top of the chamber was attached to a humidified air flow system (0.35 ml/min) similar to that described by Pratt et al. (42). Controls consisted of 1.5-cm explants acropetal to and basipetal to the abscission zone explant (Fig. la). Empty chambers were used as a check on the system. One-milliliter gas-tight plastic syringes were attached to the exhaust port of the flow chamber. The syringes remained attached without the plunger. At sampling time, a plunger was started into the syringe, the syringe was removed from the flow system, and the 1-ml sample was injected into a gas chromatograph. Gas samples were taken at 6 AM, 10 AM. and 4 PM daily for 7 days. Explant fres...