Plant Root, Stem, and Leaf Anatomy: Structure and Function

Plant Anatomy: Roots, Stems, and Leaves

Root Structure

The root has a simple structure with no central bone. It contains vascular tissue in the phloem and wood beams, along with fundamental bark tissue. The endodermis clearly demarcates these areas. Two meristems are present: the cambium, which forms a ring of dividing cells between the phloem and wood, and the phellogen, which develops in the cortical parenchyma. The phellogen produces corky tissue layers for protection and cortical parenchyma internally.

Stem Structure

Stem structure differs between dicotyledonous and monocotyledonous plants. In dicots, vascular tissue forms a cylinder with the xylem inside and phloem outside. Fundamental tissue is located between the epidermis and vascular tissue (bark) and between the vascular cylinder and the axis. The cambium is more active than in roots, producing thicker concentric layers of wood each year. Monocots have an epidermis, cortical parenchyma, pericycle, and parenchyma with many vascular bundles in concentric circles.

Leaf Structure

The leaf consists of three parts: the binding site to the stem, the petiole, and the mesophyll. The mesophyll, the bulk of the leaf, contains chlorophyll parenchyma, a vascular system, and stomata. Vascular bundles form the leaf's veins. The chlorophyll parenchyma is responsible for photosynthesis. There are two types of mesophyll cells: palisade cells, which are elongated and located on the upper side of the leaf, and spongy cells, which are irregularly shaped and located on the underside of the leaf. Stomata are interspersed among the epidermal cells on the underside of the leaves and regulate gas exchange and transpiration. They consist of two guard cells with chloroplasts, which define an opening called the ostiole, communicating with the substomatal chamber. Guard cells open or close the ostiole based on environmental conditions.