Effects of Biochar on Plastid Pigment Metabolism in Flue-cured Tobacco

To reveal the influence mechanism of biochar on the plastid pigment metabolism in flue-cured tobacco,the cell structure,gene expression and substance metabolism of cv.K326 were studied.Cell ultrastructure analysis indicated that:at the early mature stage of middle leaves,the thylakoid lamellae content in leaves treated by biochar application rate of 300 or 600 kg/ha was higher and decreased along with the development of tobacco leaves,and it decreased more obviously in the leaves without biochar application(the control).Gene expression analysis showed that:the expression of genes related to plastid pigment synthesis reduced gradually,while the expression of genes related to plastid pigment degradation increased after topping;and the expression of genes related to carotenoid biosynthesis and degradation was relatively stronger by biochar treatement at the rate of 300 or 600 kg/ha.Substance metabolism analysis suggested that:the plastid pigment content in leaves reduced gradually after topping;biochar application increased the plastid pigment accumulation in leaves.At the later stage of middle leaf maturing,the plastid pigment accumulation reached the highest in leaves treated by biochar at the rate of 300 kg/ha,while it decreased and was close to that in the control with the increase of biochar application rate.The contents of pigment degradation products and neutral aroma components in cured leaves treated by biochar at the rate of 300 kg/ha were the highest,while those in leaves without applying biochar were the lowest.Therefore,applying biochar at an appropriate rate is beneficial to the pigment metabolism in leaves at mature stage and the formation of neutral aroma components in cured leaves.