Studies On Leaf Maturity Of A Variety Of Tobacco Yunyan85

Studies were made on leaf maturity of a variety of flue-cured tobacco Yunyan85 by observing field growth days of Yunyan85 and 1(326 needed to different maturity, dissecting leaf at different maturity, testing changes of chlorophyll a,chlorophyll b, carotenoid content, detemining changes of activities of superoxide dismutase (SOD), peroxidase(POD), catalase(CAT), measuring changes of molonaldehyde (MDA) content and relative permeability of cell membrane during the maturation of tobacco leaves, and by grading cured leaves of different maturity. The results showed that the activities of SOD, POD, CAT decreased while MDA content and relative permeability of cell membrane increased with the increasing of maturity. This resulted in the accumulation of the active oxygens, which in turn not only increased the lipid peroxidation of the plasma membrane and promoted the accumulation of MDA, but also accelerated the destruction of the plasma membrane that caused the increase of the relative permeability of the plasma membrane. It induced that the leaves and the clearance of cells thinning down, the structures of leaf tissue loosening and the tomentas of epidermic falling off. With the increasing of maturity ,the chlorophyll content decreased rapidly while the carotenoid content decreased slowly, so the ratio of the chlorophyll content and the carotenoid content became bigger. Thus, the color of tobacco leaves turned from green to yellow.Results of grading cured leaves were also analyzed. Derived from all .of the above, some index of leaf maturity at the most suitable harvesting time were found out. Finally, how to use these index were discussed in detail.