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Section 2: Roots, Stems, and Leaves. Preview Roots Stems Leaves. Roots. anchored plants absorb water and mineral nutrients store organic nutrients, such as sugar and starch Highly branched, fibrous root systems are found in most monocots, such as grasses.
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Section 2: Roots, Stems, and Leaves Preview • Roots • Stems • Leaves
Roots • anchored plants • absorb water and mineral nutrients • store organic nutrients, such as sugar and starch • Highly branched, fibrous root systems are found in most monocots, such as grasses. • Many dicots have a large central root from which smaller roots branch. This is called a taproot system.
Stems • Stems support the leaves and house the vascular tissue • Many plants have stems that are specialized for other functions, such as water storage in cactus. • A plant with stems that are flexible and usually green is called a herbaceous plant.
Stems, continued • The stems of herbaceous plants contain bundles of xylem and phloem called vascular bundles. • Vascular bundles are surrounded by ground tissue. The tissue at the center of the stem of most vascular plants is called the pith. • The pith is used for storage.
Stems, continued • Woody stems, such as those of trees and shrubs, are stiff and nongreen. • The wood in the center of a mature stem or tree trunk is called heartwood. • Sapwood, which lies outside the heartwood, contains vessel elements that can conduct water.
Leaves • Leaves are the primary photosynthetic organs of plants. • Most leaves have a flattened portion, the blade, which is usually attached to a stem by a stalk, called the petiole. • A leaf blade may be divided into two or more sections, called leaflets.
Leaves, continued • A leaf is a mass of ground and vascular tissue covered by epidermis. • In leaves, the ground tissue is called mesophyll. Mesophyll cells are packed with chloroplasts, where photosynthesis occurs. • One or more rows of closely packed, columnar cells make up the palisade layer, which lies just beneath the upper epidermis.
Leaves, continued • Many plants have modified leaves that are specialized for particular functions. • For example, water lily leaves are specialized for floating on the surface of ponds. • Cactus spines are modified leaves. • Venus’ flytrap leaves are modified to catch insects.
