A ROOT CALLUS CONTROLS THE FUTURE OF YOUR CUTTINGS
Rooting Compounds can be used to promote the growth of a root callus at the damaged stem end of your cutting. This repair will happen and roots grow naturally, albeit more slowly, because of the auxins present within the cutting. The delay caused by the plant having to transport auxins from its top to the cut stem can thus be avoided.
It is important to note that the smallest amount of synthetic rooting compound should be used to avoid slowing the root growth and delaying the rooting process. A very delicate balance exists between auxins, which regulate root production and growth, and cytokinins, which regulate shoot development and growth. It is this interaction of these two hormones that is responsible for the root callus formation. If this hormone balance is upset the consequences will be dire indeed. So in this case, less is very definitely more.
When the cut stems are treated and placed in the growing medium, the stem cells have to repair themselves and organise the development of a root system, or the cutting will die. In order to achieve this calluses are formed at the cut ends. These firstly seal and repair the damage but then form new root cells.
Rooting mixes that contain auxins (IBA) must be used sparingly and for a short time only. As the roots start to grow out of the root callus tissues the presence of too much auxin will cause the formation of new root callus growth, slowing, or even stopping the new root development. Often the roots will only start to form after the rooting compound has all been absorbed and or dissipated in the surrounding medium.
There are usually three strengths of rooting compound, No1 containing 0.001% active ingredients, No 2 containing 0.004% active ingredients and No3 containing 0.008% active ingredients. Because too great a concentration of auxins will retard the root development, it is necessary to determine the cuttings own auxin concentration before proceeding. This is best done by trying a few cuttings on each strength compound and monitoring the results. You can then use the best one on your new cuttings.
Some of the rooting compounds also contain a fungicide. This type of product may help to protect the cuttings from fungal infections before the damaged stems have repaired.
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