Studies on the Biosynthesis of Lignin

We have been studying on the genesis of lignin and the changes of some chemical con stituents contained in the gourd fruits which were taken in turn in certain periods after flowering.The results obtained are as follows :(1) Lignin was at first generated on the fifteenth-day after flowering, and since then in creases rapidly and finally occupies the whole fruit.The distributions of peroxidase and phenoloxidase in the tissue of fruit agreed with the lignification, and, it is suggested that these enzymes have relations to the biosynthesis of lignin.(2) Lignin is mainly synthesized at the tissue of the shell-part of fruit.The content of lignin was only 2.3% on the fifteenth-day but it reached to 32% in hardened fruit.The methoxyl content of lignin was only 2% on the fifteenth-day but it increased along with the increase of lignin reaching to a level of 12% on the fifteenth-day, and to 15.3% after drying.In addition to these changes of lignin, other components except lignin also showed character istic changes.(3) In order to investigate the increase of the methoxyl content of lignin further, lignin was oxidized with nitrobenzene in an alkaline medium.Among p-hydroxybenzaldehyde, vanillin and syringaldehyde in that oxidative mixture, the former was the richest component in the younger fruit, but the latter two, which were richer in their methoxyl content increased with the growth of fruit, and after ripening vanillin was the richest and p-hydroxybenzaldehyde the poorest component.