Relation of the Production of an Active Emanation to Respiration in the Avocado Fruit.

The production of physiologically active emanations by plant tissue in general, and especially by ripe fruit, has been demonstrated by epinastic responses of tomato and potato leaves, by inhibition of seed germination and potato sprouting, by the triple response of etiolated legume seedlings, and by effects on fruit respiration and softening. In all cases which subsequently have been investigated chemically, the active substanee has been shown to be ethylene. This is niow so well established and generally accepted that demonstration of the activity of an emanation by any of the above methods, is a very strong indication that ethylene is among the gases evolved [ (18, 19, 20, 21) and review by BIALE and SHEPHERD (4) ]. A number of workers have found that the production of ethylene by various fruits is associated with the increase in rate of carbon dioxide output which is known as the climacteric rise in fruit respiration. HANSEN (7, 8) and HANSEN and HARTMAN (9) found that the peak of ethylene production coincided closely with the climacteric peak in the pear. KIDD and WEST (11) report that the development of the substance in apple vapor which inhibits germination of pea and mustard seeds coincides with the climacteric rise. NELSoN (14, 15) found that several varieties of apples show a pattern of varying ethylene content throughout storage life analogous to the course of carbon dioxide evolution. Subsequently (17) he compared the evolution of carbon dioxide and ethylene by the McIntosh variety. In this study it appeared that the peak of ethylene production occurred somewhat later than the peak of carbon dioxide output. On the other hand, for the banana (14, 15, 16) he found that the highest rate of ethylene evolution comes before the peak of carbon dioxide production, with a secondary peak afterward; evidence was presented that ethylene is consumed during the peak of carbon dioxide output. DENNY and MILLER (6) obtained a positive epinastic response with young potato plants subjected to the emanations of avocado fruit, and recent studies on the respiration of the avocado (2, 3, 22) have shown that this fruit has a well-marked climacteric rise. It therefore became of interest to study the relation between production of active emanations and the course of respiration.