Graft Incompatibility Related to Cambial Peroxidase Isozymes in Chinese Chestnut

Chinese chestnut (Castanea mollissima Blume) seedlings were ring-grafted with bark rings from seedlings of the same species whose cambial peroxidase isozyme banding pattern was similar to or different from that of the stock. When the isozyme phenotype of the donor matched that of the stock plant, a complete encircling cambium was formed and vascular xylem continuity was restored through the zone of grafted tissue. However, when the isozyme phenotype of the donor differed from that of the stock, vascular continuity was not restored. In some cases, the cambial cells of the donor plant died after producing a few new cells. When the donor cambium continued to function as a meristem, only parenchymatous cells were produced. Peroxidases are the only enzymes known that mediate the polymerization of cinnamic alcohols into lignin and the bonding of lignin to carbohydrates of the primary cell wall. These findings substantiate the hypothesis that plants differing in major peroxidases would not be graft compatible.