Role of chromium in growth and alkaloid content of datura stramonium : Thesis for Master of Science Botany

Abstract

Abstract : In retarding or inhibiting growth phenomena when applied at endurable concentrations. The three chromium ions were severely toxic to Datura Stramonium at 1.0 mM concentration or higher. In most instances, particu- larly at the lower levels of the ions, chromate was a better inhibitor to germination than dichromate; more prominently at the lower doses. Spraying 45 days old Datura Stramonium plants with various doses of the different chromium ions stunted the plants shortening their stem length, reducing the number and total and mean leaf area and lowering the fresh and dry weight of both organs. Still anionic chromium is more effective than the cationic form; more pronouncedly the dichromate ion. Such inhibitions were partially alleviated with increased concentration and/or number of sprays. Chromate, in particular, was stimulatory to most of these criteria of growth especially the gain in dry weight. Despite these inhibitory effects on growth and development of stems and leeves, 0.05 m M of these chromium ions remarkably initiated chlorophyll a and b accumu- lation with reduced content of carotenoids that were mostly alleviated or reversed with rise of concentration of the ions; more prominently on dry weight basis. Fur- ther spray with either chemicals did not significantly alter the initial effects produced by the first spray. Inspite of inhibitory effects of chromium (VI) compared with chromium (III) on alkaloids per plant or per unit leaf yet the percentage alkaloid , following chromium (VI) treatment was higher than chromium (III); the former increased while the latter decreased with increased number of sprays. Chromium ions interfered with the biosynthesis of the individual alkaloids; in- creasing the rate of synthesis of some of them. Such alterations depended on type of ion and/or number of sprays.