The respiration and anaerobic fermentation of tea leaf and their relationship to tea fermentation

Abstract

COMPARATIVELY little work has been carried out on the respiration of leaf tissue using manometric methods.-Kempner [1936] measured rates of respiration of whole leaves from pine, tobacco, plum and oleander, in this manner, and Allen & Goddard [1938] recorded respiration rates of strips of leaf from wheat floated in water, using the Fenn micro-respirometer. Later, Marsh & Goddard [1939, 1], using this same apparatus, investigated the respiration of carrot leaf with 100 mg. samples floated on phosphate buffer. The success of these workers encouraged us to make similar observations on the rate of respiration of tea leaf.These investigations into the respiration and anaerobic fermentation1 of tea leaf, obtained both by the manometric and by the standard Pettenkofer methods, together with manometric measurements of the rate of tea fermentatian and of simpler enzyme-substrate systems have enabled us to draw fairly definite conclusions as to the presence of the cytochrome system in tea leaf, and the almost complete inactivation of the H-carrying coenzymes (cozymase) on extensive mechanical damage to the leaf. Methods(1) Manometric method of determination of respiration rate. Disks, I in. in diameter, are punched in the centres of the second leaf of shoots consisting of two leaves and a bud. 10-15 such disks, weighing approximately 250-400 mg., constitute a fairly representative sample; in fact in only one experiment out of 20 was there any serious variation between replicates.The disks were suspended in 3 ml. water or M/15 p1iosphate buffer pH 5-8, contained in Warburg vessels. KOH, where necessary, was contained in the inner cups, rolls of filter paper being employed to ensure an adequate surface of the C02 absorbent. C02 outputs were obtained by difference between the mean uptakes of four vessels with KOH, and of another four without KOH, using the appropriate constants of the vessels for 02 and C02. For plant tissues in a medium of water this method appears to give results quite as accurate as those obtaine,d by the method of Dickens & 8tmer [Turner, 1938].In these determinations the Warburg apparatus was covered by a black cloth, thus preventing any disturbance of the 02-CO2 interchanges by photosynthetic processes.1 A careful distinction must be drawn between the two us,es of the word fermentati6n. Tea fermentation is not an anaerobic process, and to avoid confusion is always referred to as tea fermentation.1507

Tannins as hydrogen carriers in biological oxidation

“…However, as a result of work from this laboratory [Deb & Roberts, 1940] on the measurement of anaerobic fermentation in mechanically damaged tea leaf, it has been shown that in all probability there is an even greater destruction of cozymase activity in bruised tea leaf than was formerly visualized. It would appear that the residual cozymase activity in finely minced tea leaf is too low to account for more than a part of the carbohydrate oxidation that actually takes place, and consequently the possibility must be envisaged that the o-quinone of tea tannin can function directly as H-acceptor without the aid of cozymase.…”

“…For tea the oxidation of tea tannin is not directly an enzymic process but is brought about by oxidized cytochrome [Roberts, 1.940;Deb & Roberts, 1940].…”

Investigations into the chemistry of the flue-curing of tobacco

“…Methods The respiratory activity of tobacco leaf was measured essentially as described by Deb & Roberts [1940] for tea, using the Barcroft-Warburg apparatus [Dixon, 1934]. 300 mg. tobacco leaf in circles of area 1 cm.2 were weighed into each of four or five Warburg vessels and covered with 3 ml.…”