Chemical investigations of the tobacco plant. II, The chemical changes that occur during the curing of Connecticut shade-grown tobacco

Abstract

Connecticut Experiment Station Bulletin 324 changes were allowed to continue until experience showed that little further alteration was to be expected. The selection of the tobacco leaf for these investigations was made largely as the result of practical considerations. In order that the tissue may be killed before extensive change due to the removal from the plant can occur a large, thin leaf is desirable. The leaves selected should be uniform in size and as free as possible from petioles, buds, or structures other than leaf blade and vascular tissue. If elaborate studies are planned it is also necessary that the leaves should be of uniform genetic origin and chat the plants should be grown under carefully controlled conditions that are to a large extent reproducible from year to year.

Chemical Changes in the Harvested Tobacco Leaf: Part I. Chemical and Enzymic Conversions During the Curing Process

“…Values for crude fiber found before and after curing (106,208,310) are practically identical, with percentage values increasing as total weight decreases in the course of curing. Values for crude fiber found before and after curing (106,208,310) are practically identical, with percentage values increasing as total weight decreases in the course of curing.…”

“…Since these apparent changes can lead to erroneous conclusions, several authors, especially Vickery and Pucher (310,318), do not express their analytical determinations &s percentages, but as absolute amounts contained in samples of identical fresh weights. The fact that the rapidity of the decrease in weight varies with tobacco type and with different crops of the same type, partly explains, in the writer's opinion, the divergent data recorded in the literature for the composition of fresh leaves.…”

“…311 ule. Additional, still undiscovered, reactions within the leaf tissue may exist which are of greater importance than the transformations found and studied so far.…”

“…The existence of systematic trends of the nitrate content during curing (310,318). In some cases, the trend is toward an increase of nit,rates, in others, toward a decrease.…”

Respiration of barley plants III—Protein catabolism in starving leaves

“…I t follows, therefore, that unstable amide may be an important product of protein hydrolysis in living tissues, although there is little other direct evidence; Chibnall and Greenhill (1934) have recognized this possibility. In detached tobacco leaves Vickery and others (*933) detected the presence of an unstable amide fraction, and have since isolated pure glutamine and asparagine from the leaves (Vickery and Pucher 1936). While a difference in the conditions under which the detached leaves were kept makes direct comparison difficult, the unstable amide appears to change differently in tobacco leaves, only accumulating when the leaves were highly starved and yellow.…”