Monocot Herbaceous Stem vs. Dicot Herbaceous Stem

Description of Herbaceous Dicot Stems

• Herbaceous dicot stems possess an interior design similar to that of woody stems, without multiple growth rings. Because herbaceous dicots die annually they don't have annual growth rings like trees do. Instead they have only one ring. In herbaceous dicots the xylem cells are located toward the center of the stem, and the phloem cells are located toward the outside. Xylem are structures in the stem that carry water and minerals upward from the roots to the rest of the plant. The phloem carry food materials or sap down the stem to the roots. New cells for both the xylem and the phloem are produced in the vascular cambrium, which lies between the xylem and the phloem. Together the xylem and the phloem form fibrovascular bundles arranged in a circle around the center of the stem. The pith and cells in which the fibrovascular bundles are embedded are composed of parenchyma tissue which provides structural strength and food storage. An epidermis surrounds the tissue for added protection.

Examples of Herbaceous Dicots

• Herbaceous plants with dicot stems have flowering parts in multiples of fours or fives, and the leaves are typically broad and flat with branching vein patterns. The roots are usually taproots. The following is a partial list of the families of plants that include herbaceous dicots: cactus, composite, heath, mint, mustard, nightshade, pea and rose. Some plants, as the University of California Museum of Paleontology website points out, have a combination of both monocot and dicot traits, making identification of some plants a point of contention for many botanists. For instance, water lilies (Nymphaea odorata) are classified as dicots but have some monocot characteristics, as do a number of paleoherbs.

Description of Herbaceous Monocot Stems

• Unlike the fibrovascular bundles in dicots that are arranged in a ring, the bundles in the monocot stem are scattered, older bundles being closer to the center. The xylem cells sit in the inside portion of the bundles and the phloem in the outside. Surrounding the monocot stem is a hard, tough rind that provides support to the plant. The vascular bundles of the monocot stem typically do not contain cambium. A few do however. Some monocots have hollow stems with the vascular bundles being around the edge of the stem.

Examples of Herbaceous Monocots

• Unlike dicots, the flowering parts of monocots appear in groups of three. The root system is usually fibrous, and the leaves are long and narrow with veins running parallel to each other. Examples of herbaceous monocots include plants in the following families: amaryllis, arum, banana, cattail, grass, iris, lily, orchid, palm and sedge. Some monocots such as the air potato or Chinese yam (Dioscorea oppositifolia) and the black bat flower (Tacca chanitrieri) have some dicot characteristics. Nevertheless, most herbaceous flowering plants fall clearly into one category or the other.