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

Abstract

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.

Ethylene Plays Multiple Nonprimary Roles in Modulating the Gravitropic Response in Tomato1

“…Ethylene inhibits hypocotyl elongation in a variety of species, including etiolated Arabidopsis (Goeschl and Kays, 1975;Ecker, 1995;Peck et al, 1998) and yet accelerates hypocotyl growth in light-grown Arabidopsis (Smalle et al, 1997) and peanut (Goeschl and Kays, 1975). In this study we found no significant inhibition or stimulation of overall elongation within the marked region that included the gravitropic bending zone by ethylene concentrations that inhibited gravicurvature (Fig.…”

“…Applied ethylene is known to inhibit hypocotyl elongation growth in etiolated plants as part of the "triple response" phenomenon (Goeschl and Kays, 1975;Ecker, 1995). Growth inhibition due to high ethylene leads to decreased tropic responses, which are by definition dependent on growth.…”

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

“…It seems, therefore, that ethylene at 0.05 Ml L' is insufficient to rapidly induce EFE activity in preclimacteric apples as observed with higher ethylene concentrations. A semilog plot (8) shows half-maximal promotion of EFE development by ethylene at approximately 0.9 Ml L' and saturation close to 20 ul L-'. After repeated evacuation and subsequent shifting of apples from the ethylene (50 Ml L-') treatment into a stream of ethylene-free air (below 0.005 Ml L-'), EFE activity in the peel declined by half in approximately 5 d (Fig.…”

“…4). A semilog plot, as adopted by Goeschl and Kays (8), in which increase of respiration is plotted against corresponding logarithm of ethylene concentration, reveals a half-maximal stimulation of CO2 production at an ethylene concentration of approximately 1.0 Ml L' and saturation between 15 and 20 Ml L-'. Ethylene treatment causes AVG-treated apples to ripen (3).…”

Factors affecting the direction of growth of tree roots

“…Waterlogged soils are characterised by a lack of oxygen, increased levels of carbon dioxide and ethylene, together with many other chemical changes (Armstrong, 1982 (1980), and for flooded Salix (see Gill, 1970 Ycas and Zobel's (1983) experiments, ethylene at non-toxic concentrations had little effect on the direction of corn root growth, and only small effects on corn had been found by Bucher and Pilet (1982). In another study, orthogeotropic pea roots responded to ethylene by becoming diageotropic but the roots of three other species did not respond in this way (Goeschl and Kays, 1975 …”