AbstractT. volgelii leaves that were yellowed naturally by senescence or artificially by foliar applications of growth regulators showed significant increases in percent total rotenoids per unit of dry leaf weight. The growth regulators that most effectively accelerated leaf-yellowing were dicamba, 2,4,5-T, 2,4,5-TP, and 2,4-D. MH-30, 2,4,6-T amide, 2,6-DA, and 4-CPA failed to induce leaf-yellowing in T. vogelii. Leaf yellowing was accompanied by losses in dry leaf weight per unit area. This was assumed to be caused by the growth regulators lowering photosynthetic efficiencies and increasing metabolic rates, thereby lowering leaf reserves. It is concluded that leafyellowing per se did not change the absolute quantity of rotenoids per leaf; it only altered the ratio of total rotenoids to the total dry weight in a leaf.
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