When the fan leaves absorb the light from the sun, and new leaf growth appears, the stem will become thicker and stronger. When this happens, more internodes develop around the stem. The structure of cannabis plants is due to the stem, which gives structure to the cannabis plant and supports the leaves, flowers, and branches. The stem comprises a vascular system, including the phloem and xylem. These two parts of the vascular system helps give the entire cannabis plant the support and structure it needs to grow. Growers will usually cut off the top of the stem, allowing the plant to grow even more flowers.