Changes in the Chlorophyll and Carotene Contents of Curing Burley Tobacco Cut at Different Stages of Maturity

Abstract

A study was made of the changes in the chlorophyll and carotene contents of the leaves of stalk-cut burley tobacco during the air-curing process. Leaves from the upper and lower parts of plants, cut when 10 days immature, mature, and 10 days overmature, cured at 68% relative humidity and 23.8[degree]C in air-conditioned chambers, were analyzed. The initial chlorophyll and carotene content of the leaves decreased with increasing maturity, and was higher in the upper than in the corresponding basal leaves. Low chlorophyll concs. were reached in a shorter time of curing in the overmature than in the immature top leaves since the rate of loss was not greatly affected by maturity. The highest rates of chloro- phyll loss were observed in the basal leaves of immature plants, indicating that translocation of some substances to the immature top leaves may have occurred. As the total chlorophyll content of the leaves reached low values the chlorophyll a:b ratio decreased. The carotene in the leaves did not disappear as completely as the chlorophyll, but graphs showing the carotene changes were similar to the corresponding graphs of chlorophyll changes for each stage of maturity. A decided change in the rate of loss of carotene and of chlorophyll and in the chlorophyll a:b ratio occurred at a fairly definite moisture content (65-70% moisture), though the time required to reach this point depended upon the maturity of the leaves when cut.