Anatomical Changes And Immunogold Localization Of IAA In Cells Of Hickory's Graft Union

Hickory (Carya carthayensis Sarg.) is China's unique high-quality dry fruit tree and woody oil plant. It has high economic value, but the juvenile stage is long, and seeds late in natural conditions. Grafting can effectively shorten the period of juvenile, bring forward seeding, expand the scope of adaptability, but homoplastic grafting technology is difficult, and the survival rate is low. In order to improve the hickory grafting technology, enrich the grafting theory, reveale IAA distribution and changes in the cells in the course of hickory grafting, confirm the function mechanism of IAA in the healing process of hickory grafting, we used light microscopy, transmission electron microscopy, and immuno-gold localization technique to study the anatomical changes of graft union in hickory's shoot homoplastic plants and subcellular localization of IAA in graft union. The main results are as follows:1. The results of anatomical changes of graft union in hickory's shoot homoplastic plants showed: The union processes included the formation and thickeness of isolation layer(1-6 d); the growth of calli and the disaggregation and disppearence of the isolating layer(7-12 d); the formation and linkage of the vascular bridge(14-23 d); the differentiation and connection of vascular tissues(24-40 d). The primary change was the formation of the isolating layer. It was firstly formed in the cambium zone on the first three days after grafting,thickened in the next three days and disaggregated after the contents absorbed by the callus cells, at last disappeared on the 12th day, and sieve elements were differentiated at that time. With the formation of the vessel elements 14 d after grafting, vascular bridge began to set up and link up. At last the vascular tissues differentiated and contacted with each other, the whole process of reuion was over. The stock and scion became a whole body and transportation between them was carried out in a normal way. A series of wound responses in callus cells were induced during this process. After grafting, the plasmodesmata near grafting face were closed and others were active in transportation. The matrix got through the degraded cell walls and fused in some cells near the isolating layer. The quantity of organelles such as Golgy bodis, mitochondria, and endoplasmic reticulums was increased. Many multi-vesicular bodies and paramural bodies were observed, the starch granules stimulated at the beginning and disappeared afterward.2. The results of subcellular localization of IAA in the cells of hickory graft union showed: immuno-response of IAA in the calli was special, and IAA mainly located in the starch granules in the plastids. Plastid was the main source places of IAA. The IAA level was highest on the 7th d in stocks and 6-7th d in scions.IAA played an important role in the formation and differentiation of calli and vascular tissues. Probably, wound after grafting firstly induced the release of combined-IAA, start wound responses, then reset the polarity of signal transduction, and consequently induced the differentiation of vascular tissues from calli.