Stele is also used more loosely. There are 3 basic types of steles in vascular plants 1. In stems the phloem surrounds the xylem, in roots the phloem is located between the xylem arms. E.g., fern stems 2. We are going to talk about stems today and leaves next week.
Stems support the plant upright.
They function in conduction. Basically they support the photosynthetic organs, the leaves in a favorable position for exposure to the light. Leaf primordia -young leaves, these develop into the mature leaf. Remember when we talked about the formation of lateral roots last time we mentioned the term endogenous. I.E. the new roots develop on the inside of a mature root and punch their way out through the cortex.