Plant Biology Root and Stem Structure

Root Structure

• Roots anchor plants, absorb water and minerals, and store food.
• The root tip is protected by the root cap, which secretes mucilage and sloughs off cells as the root grows through the soil.
• The root apical meristem is located behind the root cap and produces all new cells for primary growth.
• The primary tissues of the root include the epidermis, cortex, endodermis, pericycle, and vascular cylinder.
• The cortex contains amyloplasts, which are starch-containing plastids.
• The endodermis regulates water flow to the vascular tissue.
• The pericycle can become meristematic and produce secondary roots.
• The vascular cylinder contains xylem and phloem.

Stem Structure

• Stems support the plant, transport water and solutes, and sometimes photosynthesize and store food.
• The shoot apical meristem is located at the tip of the stem and produces young leaves and axillary buds.
• Nodes are points on the stem where leaves attach.
• Internodes are the portions of the stem between nodes.
• The epidermis of the stem is coated with cutin, a waxy waterproof substance.
• The cortex stores food.
• The pith in the center of the stem also stores food.
• Collenchyma cells provide support for elongating regions of the plant.
• Vascular cambium is located between the xylem and phloem and produces secondary growth.
• Bark includes all tissues outside of the vascular cambium, including the secondary phloem.
• Periderm replaces the epidermis when it ruptures due to secondary growth, and is produced by the cork cambium.

Leaf Structure

• Leaves are the primary sites of photosynthesis.
• A leaf typically consists of a blade and a petiole.
• Simple leaves have one blade, while compound leaves have multiple leaflets.
• Veins are arranged in different patterns, including parallel, pinnate, and palmate.
• Phyllotaxis refers to the arrangement of leaves on a stem, which can be opposite, alternate, or whorled.
• The epidermis of the leaf contains stomata, which are pores surrounded by guard cells.
• Palisade mesophyll cells are closely packed and contain chloroplasts.
• Spongy mesophyll cells are irregularly shaped with air spaces.

Additional Information

• Monocots have one cotyledon, while dicots have two.
• Cotyledons are the leaf-like parts of a plant embryo found within a seed.
• Endosperm surrounds the embryo and provides nutrition.
• Root hairs increase the surface area of the root for absorption.
• Xylem transports water and minerals from the roots to the leaves.
• Phloem transports food from the leaves to the rest of the plant.
• Stomata regulate gas exchange and water loss.
• Air spaces near the lower surface of the leaf allow for gas exchange.
• Stolons are horizontal stems that produce new plants at their nodes.
• Rhizomes are underground stems that store food and water.
• Tubers are modified underground stems that store food and can produce new plants.

This quiz covers the essential structures and functions of roots and stems in plants. Topics include the role of various tissues such as the root cap, cortex, endodermis, and the shoot apical meristem. Test your understanding of these fundamental concepts in plant biology.