the excised stem cutting is a wound response. At a molecular level when a cutting is first excised at the stem there is an immediate increase in jasmonic acid, known to be necessary for adventitious root formation. When the cutting is excised from the original root system the root inhibiting hormones, cytokinin and strigolactone, which are made in the root and transported to the stem, decrease in concentration. Polyphenol degradation decreases, increasing auxin concentration. The increased auxin concentration increases nitric oxide concentration which initiates root formation through a MAPK signal cascade and a cGMP-dependent pathway that both regulate mitotic division and are both necessary for the initiation of adventitious root formation. The root primordia form from cambial cells in the stem. In propagation of detached succulent leaves and leaf cuttings, the root primordia typically emerges from the basal callous tissue after the leaf primordia emerges. It was known as early as 1935 that when indolyl-3-acetic acid (IAA), also known as auxin, is applied to the stem of root cuttings, there is an increase in the average number of adventitious roots compared to cuttings that are not treated. Researchers also applied this compound to stems without leaves that normally would not have any root formation and found that auxin induced root formation, thus determining auxin is necessary for root formation. Identification of this hormone has been important to industries that rely on vegetative propagation, as it is sometimes applied to fresh cuttings to stimulate root growth. Technique Some plants form roots much more easily than others. Stem cuttings from woody plants are treated differently, depending on the maturity of the wood: Softwood cuttings come from stems that are rapidly expanding, with young leaves. In many species, such cuttings form roots relatively easily. Semi-hardwood cuttings come from stems that have completed elongation growth and have mature leaves. Hardwood cuttings come from fully matured stems, and are often propagated while dormant. Most plant cuttings are stem pieces, and have no root system of their own, and are therefore likely to die from dehydration if the proper conditions are not met. They require a moist medium, which, however, cannot be too wet lest the cutting rot. A number of media are used in this process, including but not limited to soil, perlite, vermiculite, coir, rock wool, expanded clay pellets, and even water given the right conditions. Most succulent cuttings can be left in open