Simunary. Pea epicotyls (PisuniI satikl'u,,, cv. Alaska) were enclosed in chamibers in which their elongation was restricted by means of a foam neoprene stopper or by a medium of glass beads. These treatmentii increase(l evolution of ethylene and restllted in reduced length and increased dianmeter of both the internodes and the cells of the internodes. These responses increase(d with increasinig degrees of restriction. A time-sequenice study of the emergence of epicotyls through 90 mm of glass beads showed that all accelerated evolution of ethylene precede(d a reduction in elongation. As the epicotyls elongated through the glass bead mediumii and less resistance was encounitered, evolution of ethylenie decline(l and rapid elonigatioi was resumed.

Summiarv. The produiction of ethylene by etiolated pea epicotyls (Pisuim sativum11 L., cv. Alaska) is confined to the plumule and plumular hook portion of the epicotyl, and occurs at a rate of about 6 pLlkg-l.hr-1. Such a rate is sufficient to give physiologically active concentrations of ethylene within the tissue. Exposure of etiolated seedlings to a single dose of red light caused a transient decrease in ethylenc produiction and a corresponding increase in plumuilar expansion. Far-red irradiation following the red light treatment decreased the red effect to the level achieved by the far-red alone, suiggesting that the ethylene produiction mechanism is controlled by phytochrome and thuis that the ethylene intervenes as a regulator in the phytochrome control of pltimuilar expansion.A relationship between the production of ethylene an(l the inhibition of plumular expansion in etiolatedI pea epicotyls can be 'deduced from several recent observations. First, the rate of ethylene productioin in the growing epicotyl does not increase in proportion to the increasing mass or ntumber of cells (5)

The growth rate of rice coleoptiles is increased by low concentrations of ethylene, especially in oxygen concentrations lower than air; carbon dioxide enhanced this response. C2H4 is produced by rice seedlings, and this production is also enhanced by carbon dioxide. Ethane and propane were produced in trace amounts but were inactive in growth stimulation as were also methane, propylene, and butane.

No abstract

Dormant potato tubers (Solanum tuberosum L.) of two cultivars were treated with various concentrations of ethylene gas for various exposure periods. As has been shown by others, ethylene caused a rapid but transient increase in respiration rate, which appeared to be independent of any effects on dormancy. All concentrations tested caused accelerated sprouting, 2 microliters per liter being the most effective. Ethylene exerts a dual effect on potato tubers: it markedly shortens the duration of rest, but it inhibits elongation of the sprouts during extended treatment. Comparing these results with published work on seeds, bulbs, and corms suggests that ethylene must have a significant but as yet unexplained role in rest and dormancy. However, since the most effective ethylene treatment did not equal the response elicited by treatment with ethylene chlorhydrin, other factors must also contribute to termination of rest.The initiation of sprouting in potato tubers is accompanied by a variety of biochemical changes which are usually reflected in changes in hormonal concentration, respiration rate, and the onset of nucleic acid synthesis and cell division and enlargement (16, 21, 24-26, 30, 31). A number of reports have supported the hypothesis that the rest period in potato tubers is regulated by gibberellins and ABA (24,26,30). However, the significance of other hormones, particularly of ethylene, has not been investigated adequately.That ethylene is an endogenous growth hormone for plants and a potent growth regulator is well established (1,23), but its role in the dormancy of potatoes and other plant organs has remained unclear. The older works on potato present conflicting evidence (4, 5), and there has been little clarification in recent work. Terminating dormancy in freshly harvested potatoes is an important practical problem, to which much attention has been given, and many chemical treatments have been tried (5,22). Rosa (28) was first to try ethylene; concentrations of 10, 200, and 1000 ,ull were applied for 28 days giving substantial increases in the stand obtained 1 month after planting. On the other hand, Denny (8, 9) tried ethylene, propylene, and acetylene at 1000 and 10,000 ,lll for 4 and 7 days and found them to be ineffective. In studies by Vacha and Harvey (32), ethylene treatments with 1000 ,ul/l at 20 C for 6 days gave 'This investigation was supported in part by North Atlantic Treaty Organization Research Grant 541 to L.R.2 On leave from Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. earlier sprouting and faster growth with some potato cultivars. Rosa (29) reported further tests with ethylene, using treatments of 455 and 2500 ,ul/l for 2, 3, or 4 weeks at 22 C; the 2-and 3-week treatments inhibited sprouting, whereas a 4-week treatment promoted sprouting (no difference between the concentrations was observed). In a better planned experiment with 800 ,1/1, ethylene accelerated emergence, especially in the shorter treatments. Another experiment with 500 1ul/l g...

No abstract

Fruits of Chinese gooseberry (Actinidia chinensis Planchon, cv. Bruno) were harvested and respiration rates and other attributes were measured at regular intervals throughout the season. The fruit matured at about 23 weeks after anthesis as shown by patterns of respiration, response to ethylene treatment and changes in texture and content of soluble solids. Fruit growth followed a unique triple sigmoid curve. Natural ripening showed the fruits to be of climacteric type but, although associated with a peak of ethylene production, the respiratory pattern was somewhat atypical and initiation of ripening within any lot of uniform fruits was very variable. Ethylene treatment stimulated ripening in fruits of all ages, but a large induced respiratory peak was seen only in immature fruits. The physiological observations confirmed present horticultural practices and provide a basis for development of objective enforceable quality grades.

Ethylene gas in minute quantities plays an important role in plant metabolism, especially in the ripening of fruits. A sensitive quantitative analytical method has long been needed. In the method reported here, ethylene is absorbed from an air stream in a solution of mercuric perchlorate, forming an ethylene-mercury complex. The accumulated ethylene is later released from the complex by the addition of hydrochloric acid, and its volume is measured manometrically. This method THYLENE gas in minute quantities plays an important role E in plant metabolism. It stimulates marked physiological changes, such as an increase in respiratory activity and such chemical transformations of reserve materials as the change of starch to sugar. The hastening of ripening of fruits by use of ethylene gas has been knoRn for many years (4,11). Later it was discovered that naturally ripening fruits themselves produce ethylene which may have a significant influence on the storage life of other fruits in the same chamber. Chemical proof now exists of the production of ethylene by apples, pears, bananas, avocados, and the fungus Pentczllium dzgzfatrrm. Biological evidence suggests that many kinds of fruit and other plant tissues do likewise. The role of ethylene in the physiology of fruits has recently been reviewed by Bide ( 1 ) and by Porritt (14).In view of the physiological role of ethylene, it was realized that a rapid method for quantitative estimation of this gas in small amounts was a prerequisite for further advance in this field. Such a method must be specific, at least for olefins, and efficient is best suited for ethylene concentrations of 0.5 p.p.m. and higher, though not more than 0.05 p.p.m. will escape absorption. Total amounts of ethylene as low as 0.2 ml. can be determined with an accuracy of 5%, while a higher accuracy can be obtained with larger amounts. Although the method is specific for olefins only, no gaseous olefin other than ethylene is known to be produced by plants. -4 number of other volatile products of plant metabolism were tested and did not interfere.enough to remove and accumulate ethylene from a moving gas stream, even though less than 0.1 p.p.ni. might be present. The available methods did not fulfill these requirements.Nelson (IS) used permanganate oxidation after presumably removing nonethylene volatiles by absorption with sodamide. In addition to questionable selectivity, the method had systemic errors, making a correction necessary. Christensen et al. ( 2 ) modified the bromination method of Davis et al. ( 3 ) for use on a micro scale, and this has been further modified by Hansen and Christensen (9) and by Hansen (8). I t has the disadvantage of maintaining the fruit samples in a static atmosphere, causing ethylene to accumulate to a concentration of a t least 25 p.p.m. Under certain conditions concentrations of this magnitude will accelerate respiratory activity and may cause increased ethylene production. Walls (19) used a wet oxidation, absorbing the ethylene from a gas stream in silver-activate...