A petiole is a stalk that supports a leaf in a plant and attaches it to the stem. It is not the same as a stem, which is the main source of support and produces nodes and roots. A petiole can have different shapes, sizes and textures depending on the plant species. For example, a celery stick is actually a petiole of the celery plant, while some leaves have no petioles and are directly attached to the stem (sessile). The main function of the petiole is to transport water, nutrients and energy between the leaf and the rest of the plant.