Eight factors affecting the survival of grafting

Before   , walnut grafting was difficult, and the survival rate was low, but it was not solved until around 2000, and the grafting survival rate increased to more than 90%, and grafting workers everywhere can skillfully master this skill. Generally speaking, there are many factors affecting the survival of walnut grafting, and special attention should be paid to the following aspects in production.

Quality of    1, rootstock and anchovy in terms of survival mechanism of grafting, only rootstocks and grafts can produce enough callus and callus can differentiate into connective tissue before a new plant can be formed at last. This requires that rootstocks and scions have strong vitality, especially according to the quality of grafts, because grafts have to rely entirely on their own stored nutrients for a period of time, if the quality of grafts is poor, the survival rate will be greatly reduced. Therefore, in production, it is necessary to avoid using poor quality scions, the pith of branch grafting should be small, the buds should be full, and the grafts of bud grafting should be Lignified or semi-lignified. The bud quality at the base and tip of the branch is poor and can not be used for grafting.

When    buds are grafted, the rootstock seedlings are generally sown in the spring of the first year, and then stubble in the spring of the second year, and the new shoots are grafted from the end of May to the middle of June. The thickness of the grafting part of the rootstock is required to reach 1-2. 5 cm. If the grafting is carried out in the 2-year-old site, the survival rate will be greatly reduced. Some people vividly call the grafted walnut seedlings "three crutch seedlings". The first turning is the 2-year-old part of the rootstock, the second turning is the new shoot growing in the same year, and the third turning is the grafted variety.

The grafting of    buds should be cut at the end of May and the middle of June. at this time, the growth of new shoots of walnut is generally not very large, the maturity of buds is low, and there are not many buds available on a branch. in order to obtain high quality scions, the mother plant can be planted in greenhouse or greenhouse to make it germinate early. when grafted in the field, the growth time of grafted twigs is longer, the growth is large, the buds are full, and the maturity is high. The survival rate is high after grafting. On the same developing branch, the middle and lower buds are well developed and can be used as grafts, but the development quality of the top and base buds is poor and generally can not be used. Note that the budding branches can not be used as scions. It is better to collect the grafted scions during the dormant period, which is generally cut before sprouting.

   2. Bleeding is an important factor restricting the survival of walnut grafting. The bleeding fluid will make the graft interface anoxic and inhibit the respiration of anvil and anvil, thus preventing the formation of callus. In the past, walnut grafting was mainly branch grafting in spring, but walnut bleeding was particularly obvious in dormant period, and increased under the bad environment of low temperature, high humidity and more Rain Water. Generally grafted in summer and autumn to reduce bleeding. When grafting in spring, cutting a few knives near the ground below the interface as a "drain", or cutting the stock in advance, leaving water branches, delaying the grafting period, etc., can slow down the occurrence of injury, but it is difficult to avoid it completely. There is no bleeding when the seedlings are grafted indoors, which is the theoretical basis of indoor grafting of walnut in the past.

   3. Phenols are mainly affected by tannins, because walnut branches contain more tannins, and tannins are often precipitated at the interface to form an isolation layer, which hinders the bonding of anvil and anvil. There were less phenols in grafting from the end of May to the beginning of June, and the survival rate of grafting was greatly increased.

   4, environmental factors

The formation of callus in    (1) temperature walnut grafting is the key to the success or failure of grafting, and the formation of callus is closely related to temperature and humidity. According to the experiment, the optimum temperature for callus differentiation of walnut is 29 °C, and the suitable ambient temperature for grafting is 25-30 ℃. Therefore, the grafting in spring should not be too early, and it is generally carried out in the bud and leaf expansion period. The branch grafting is earlier and the bud grafting is later.

The microenvironment of    (2) humidity interface is very important for the formation of callus, mainly to maintain a certain humidity, the interface is easy to dry parenchyma to death, can not differentiate into callus, too high, poor ventilation, callus can not be produced. Therefore, plastic film is often used to wrap the interface in production to prevent the loss of moisture. In the past, indoor grafted rattan paraffin and split grafted with wet soil were all embedded in order to improve humidity.

   (3) rainfall callus formation needs higher humidity, but rainfall will seriously reduce the survival rate of grafting. Rainfall in spring will increase the occurrence of bleeding, while falling in summer will make the grafting site lack of oxygen and prone to mildew.

   5. During the grafting period, the key to ensure the survival rate of bud grafting is to choose a good grafting period. The end of May to the beginning of June is the most suitable, and the seedlings can be formed in the same year of grafting. The second is supplementary grafting in August, after the grafting survived, the buds did not germinate in the same year, and the seedlings could be formed in the second year. In the period of branch grafting, it is better to spread leaves after grafting, at this time, the bleeding is less and the survival rate of grafting is high.

   6. The skilled grafting technology can shorten the exposure time of rootstock and cuttings in the air during grafting, reduce the oxidation of tannins, at the same time, the smooth cutting surface can make the rootstock and rootstock contact closely, and the callus can be easily connected. In addition, the strong binding, airtight or not will also affect the survival of grafting. In terms of grafting method, the survival rate of square block bud grafting is the highest, which can reach more than 95%, and the survival rate of branch grafting is lower. No matter branch grafting or bud grafting, the survival rate was high when the contact area of anvil and anvil was large, and vice versa.

   7. Management after grafting many grafting failures are caused by negligent management after grafting. The branches should be tied to the struts so that the new shoots will not be broken by the wind. Budding should pay attention to timely release, release the plastic strip, reduce the hindrance of water and nutrient supply. The unbound plastic strip inhibits the growth of the binding site, which makes the binding site too fine, and the grafted seedlings are easy to break from the constriction of the graft interface. No matter bud grafting or branch grafting, it is necessary to wipe off the germinated rootstock buds in time and concentrate nutrients for bud growth, which can also improve the survival rate.

   8, rootstock, rootstock, grafting affinity is the ability of rootstocks and grafts to connect normally and form new plants. Usually, common walnut as rootstock grafting common walnut, iron walnut as rootstock grafting bubble walnut, strong affinity. Several other rootstocks, such as hickory, maple poplar and Juglans mandshurica, are far from common walnut, and their affinity is poor. For example, the phenomenon of "big feet" often occurs after the grafting of maple poplar, the preservation rate is low after survival, and it will die after growing for a few years or decades, and the life span is short.