A brief discussion on the grounding of the Xianren-like plant triangular joint
About the experience of succulent plants, a brief discussion on the grounding of the Xianren-like plant triangular joint, what follows is a comprehensive introduction.
Recently, many flower friends have been discussing the issue of how to ground the triangular joint, especially focusing on the retention or removal of the triangular pith. Of course, many Xianren and common arguments believe that retaining the triangular pith of the joint leads to the induction of triangular roots; while completely removing the pith induces self-roots of the joint. Among them, the operation of retaining the pith is easier, while removing the pith is relatively difficult.
I am cautious about this common view. Based on my own practice and theoretical support, I feel that the issue of retaining or removing the triangle is much more complicated than we imagine.
Before discussing this issue, I would like to define several concepts with you: first and foremost, the concept of "pith," which generally refers to the residual central large vascular bundle group of the triangle. Due to the highly fibrous nature of the vascular bundle, it forms what is called xylem, hence the name "pith." However, if we remove the flesh from the lower part of the residual triangle and retain the large vascular bundle, after thorough drying, the so-called "pith" at the distal end is actually just a cavity without biological activity, because the cellular material with germination ability has dried up, leaving only a cavity. The proximal end of the "pith" retains cellular material with germination ability, often from which the roots of the triangle are produced. The inner cell components of such pith are a light green tissue, lighter in color than the flesh of the triangle, which we call "medulla."
In order to clearly define this concept, we refer to the central large vascular bundle group composed of pith and medulla as the "triangle medulla."
The triangle medulla includes the fibrous tube formed by the pith and the meristematic cell tissue formed by the medulla. The meristematic cells of the medulla can form triangular roots, while the fibrous tissue of the pith has no germination ability.
After defining these concepts, it is easier for us to discuss the relationship and interaction between the triangle of the rootstock and the scion during the grafting process, which is crucial for understanding the grounding of the triangular joint.
In order to understand this physiological process more clearly, we divide the changes of the scion grafted onto the rootstock into four stages according to anatomy:
Stage 1: Healing and recanalization stage, where the incised surfaces of both the scion and rootstock exude tissue, the vascular bundles combine, and the transport channels recanalize, followed by the formation of a cellulose isolation membrane or cell infiltration fusion on the remaining wound. This process occurs within 7 days after grafting. It often determines the success or failure of the graft, and at this time, it is highly susceptible to infection, the union between the scion and rootstock is very unstable, and the scion can be easily dislodged. It is also sensitive to the environment, especially dryness, which greatly affects the closure of the vascular bundles and the fusion of the tissue exudate. The pathological and physiological changes in this part are discussed in articles about grafting and are not elaborated here.
Stage 2: Physiological fusion stage, which occurs a few weeks to several months after grafting. The phenomenon during this period is the crawling and reinforcement of cells at the vascular bundle junction and the formation of winding recanalization vascular bundles, often accompanied by excessive proliferation of胶y tissue compressing the vascular bundles. The biggest factor affecting this process is the alignment of the vascular bundles between the scion and rootstock, because the pith is a large collection of vascular bundles, so the alignment of the vascular bundles is particularly important. The common view is to recommend that the vascular bundle rings should be relatively aligned, either directly or laterally. In the second stage, the vascular bundles of the scion and rootstock have not yet appeared obvious cell infiltration, and the fusion surface is flush with the grafting surface. The scion begins to grow.
Stage 3: Infiltration negative balance stage, as the scion begins to grow, the triangle continuously supplies the scion with nutrients and a large amount of positive growth regulators, which can promote rapid growth and maturity of the scion, manifested as accelerated growth rate and early appearance of traits, etc. Due to the rapid growth of the graft and the fast metabolism of hormones, the junction between the triangle and the scion constantly shows excessive cell proliferation, and the original triangle callus cells quickly crawl and infiltrate the scion vascular bundles in order to form a more unobstructed vascular bundle to provide more nutrients. The source of this effect is likely due to the stimulatory effect of cytokinins, which are secreted from the root part and transported upwards to the scion. Due to the action of cytokinins, the sphere can have a rapid recovery growth momentum before it fully recovers growth, and it is precisely this momentum that causes the sphere to have a continuous stretching effect, leading to the expansion of the sphere's water storage and肥大, and starting to grow. This effect can last for several years until the base of the sphere shows signs of aging. Under the reverse stimulation of cytokinins, and the stretching effect of the rapid recovery of the scion's growth point, the scion tissue wraps around the triangle medulla, and the medulla cells infiltrate the scion. When dissecting a triangle grafting bag of 3-5 years, it can be found that the medulla cells of the triangle medulla have infiltrated to about one-third of the lower part of the sphere, much higher than the grafting plane.
Stage 4: Infiltration positive balance stage, with the aging of the bottom of the scion, the aging and lignification of the triangle medulla, the fixation of mixed cells at the junction, the slowing of cell division, and the decline of hormone metabolism, especially the reduction of cytokinin secretion and receptor downregulation, all these factors will limit the further growth of cells at the junction, slow down the infiltration of triangle medulla cells into the scion, and fix the junction surface between one-third and one-half of the sphere's lower part.
In fact, our grounding mostly occurs after stage 3, so at this point, an无可厚非 question is that the medulla tissue of the triangle has penetrated into the scion and has no obvious boundary with the lower vascular tissue of the scion, and even a few triangle medulla cells have infiltrated the surrounding vascular bundles of the scion. In this case, no matter what method is used to remove the pith or the triangle medulla, it is impossible to completely remove the medulla cells. Of course, unless it is precise microsurgery, it may be possible to completely remove the triangle medulla cells, but achieving this goal may require hundreds of years.
Therefore, the formation of triangle roots is unavoidable. If we conduct a detailed study of the grounding of triangles with triangle medulla, we can find at least three types of root formation:
1. Triangle roots: This is a relatively simple triangle root system formed by the residual triangle medulla cells, a typical decay root. It is more suitable for planting in acidic soil containing humus. Triangle roots generally appear within a few months to 3 years and are later replaced by junction roots.
2. Junction roots: This concept is very important in the grounding of triangle joints. It refers to the mixed tissue formed at the junction of the scion and rootstock, including medulla cells, scion meristematic cells, and fused cells. This mixed tissue forms a transitional root, which is neither like a decay root nor like a scion root, and has a soil requirement that leans towards the scion. Junction roots appear approximately 2-5 years after the core grounding.
3. Scion self-roots: These are roots formed entirely by the meristematic cells of the scion, which can gradually transform into a morphology similar to that of a real root but still has some differences from a real root. Scion self-roots can swell and form so-called "turnip roots." This process occurs after the death of the junction roots and forms approximately 3-5 years after the core grounding. At this time, the soil should be suitable for the scion itself.
According to this analysis, it can be seen that most of our current core grounding is actually limited to the formation of junction roots first. Only a few varieties (such as peonies) may form self-roots directly under specific conditions. With the core grounding, there is no doubt that triangle roots will form.
If the pith is retained too long during the core grounding, the lower end of the pith has actually dried out, and the medulla cells inside have died, lacking the ability to develop roots and are prone to secondary infection. Therefore
The withered pith without medulla must be removed as a potential hazard. The part that forms roots is the upper part with medulla, which forms triangle roots from medulla cells.
Here are a few strategies for quickly transitioning to a root system:
1. Starvation rooting method: Suitable for varieties that easily produce aerial roots, such as peonies. Stop watering the triangle at the beginning of summer, cover the sphere with a plastic bag, and maintain enough air humidity inside the bag. By the following spring, you can see a large number of thick aerial roots forming at the bottom of the scion, while the rootstock triangle is as thin as paper. This can be directly broken off, leaving the junction, properly dried, and then grounded. Due to the formation of "starvation gradient," the receptor of the scion is downregulated, allowing for the quicker completion of its own root system, forming self-roots. However, this method is not suitable for varieties that do not easily produce aerial roots.
2. Induction method: This method uses the high humidity requirement of triangle roots. Since decay types prefer humus and humidity, we can transplant the scion with triangle roots into a matrix suitable for the scion containing limestone, which can inhibit triangle roots and induce scion roots. However, the drawback of this method is that the scion and rootstock must have obvious physiological differences in root systems. Sometimes we use a simplified induction method for triangle grafting bags, leaving the core scion until the triangle medulla forms roots and dries up, and then potting it.
3. Transition method: This is the most commonly used, most effective, and safest method. It is the grounding method with a small amount of medulla tissue. Localize the pith or remove the triangle medulla. Although this rooting is slower than retaining a long pith, it converts to self-roots very quickly. In cultivation, the soil transition during transplanting should also be determined based on the specific situation. For triangle roots, humus can be added, and for junction roots and self-roots, an appropriate proportion of soil suitable for the scion should be gradually added until self-roots are produced. This process may take a few years.
The above discussion on the grounding of Xianren-like plant triangular joints is brought to you, hoping to bring a little help to your life!