Comparative Study On The Growth Of Pecan Grafted Seedlings With Different Type Of Rootstocks

Pecan(Carya illinoinensis) belongs to Juglandaceae family, Carya genus. It’s native to North America, which is excellent for nuts and landscape. This tree species is naturally tall due to its biological characteristics. The most effective way to dwarf the tree is to choose the dwarf rootstock. In this study, we used common rootstocks and dwarf rootstocks for grafting. We analyzed the differences between common rootstock and dwarfed rootstock by investigating the growth potential, anatomical structure, photosynthetic characteristics, oxidase activity and endogenous hormone content of different type rootstocks and grafted seedlings. This study was supposed to find how rootstocks influence grafted seedlings, thus can provide theoretical basis for breeding pecan dwarf rootstocks and studying the dwarf mechanism. The main results were as follows:1. The annual growth of different types of grafted seedlings had significant differences. The growth potential of rootstocks was significantly related to its grafted seedlings. The annual growth of dwarf rootstock grafted seedlings was significantly lower than common rootstock grafted seedlings.2. The characteristics of dwarf-stock-grafted seedlings was significantly related with the ratio of xylem and tegument at xylem proportion. The dwarf trend of plant was more obvious when the ratio was and the density of xylem vessel was lower.3. Seedling height of the dwarf-stock-grafted seedlings was significantly positive correlation to the ratio of xylem and tegument and xylem in stem of the dwarf stocks. Dwarf anvil stems of the ratio, the greater the dwarf anvil grafting seedling height and The dwarf trend was more obvious if the growth of seedling was slower and the ratio is larger.4. The growth of dwarf-stock-grafted seedlings was mainly related to spongy tissue and palisade tissue. The rootstock leaf has higher ratio of spongy tissue and palisade tissue. The grafted seedlings dwarf trend was more obvious. The dwarf stock characteristics was probably due to the low chlorophyll content and the weak photosynthesis.5. The seedling height of dwarf-stock-grafted seedlings was negative correlation with IOD and POD enzyme activity of dwarf stocks. The higher enzyme activity the IOD and POD resulted in more obvious dwarf effect to the plant.6. The seedling height of dwarf-stock-grafted growth was negative correlation with ABA content and ABA/GA, while it had positive correlation with ZR/GA. The higher ABA content in plant led to more obvious dwarfing characteristics.