Manometric Determination of Low Concentrations of Ethylene with Particular Reference to Plant Material

Abstract

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...

Promotion of Softening and Ethylene Synthesis in Bartlett Pears by 3-Methylene Oxindole

“…Ethylene was collected from the ventilating gases according to a method by Young et al (16) mined by gas chromatography following previously described methods (8). Fruit softening was measured using a MagnessTaylor fruit pressure meter as previously described (8).…”

Interaction of Carbon Dioxide and Ethylene in Overcoming Thermodormancy of Lettuce Seeds

“…Potassium hydroxide (20% w/v) was used to trap the CO2 from the sealed flasks and mercuric perchlorate (G. Fredrick Smith Chemical Co.) (0.25 M) in 2.0 M perchloric acid (28) was used to trap the ethylene.…”

Relationship between Ethylene Evolution and Senescence in Morning-Glory Flower Tissue

“…In this case, the low rate of ethylene production following inhibitor treatment (< 1% of control value) could suffice to elicit the slow spontaneous rolling up response observed. To test this possibility, the effects on rolling up of a high CO2 level (4% v/v) and of a mercuric perchlorate trap for ethylene (15) were examined, using both inhibitor-treated and untreated rib segments. Burg and Burg (2) …”