Final answer:
The subject of the question is biology, and the technique being referred to is called layering, which is used in plant propagation.
Step-by-step explanation:
The subject of your question is biology.
The technique you are referring to is called layering. Layering is a method used in plant propagation, where a stem is bent and covered with soil to encourage root growth. In the specific technique you mentioned, a wire is inserted through the calyx (the green outer part of the flower) and bent downward along the stem. This helps to secure the stem and promote root formation.
An example of a plant that can be propagated using this technique is jasmine or bougainvillea. The stem is bent, and the wire is inserted through the calyx, allowing new roots to form when covered with soil.