Bean stem, LM

Bean Stem. Light micrograph (LM). A bean is the seed of one of several genera of the flowering plant family Fabaceae. The genus contains more than 2, 000 different plant species of vegetables used for human or animal food. Beans have a dicot stem vascular arrangement. Vascular tissues transport water and dissolved substances inside the plant and helps support the stem. The two types of vascular tissue are xylem and phloem. Xylem carries water and dissolved ions from the roots to stems and leaves. Phloem carries dissolved sugars from the leaves to all other parts of the plant. Xylem has two kinds of conducting cells, tracheids and vessel elements. Ground tissue of the stem (called pith and cortex) develops support cells to hold the young plant upright. The dicot stem has a distinct ring of vascular bundles. Magnification: x20 when printed at 10 centimetres wide., Photo by STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY