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Plant Form and Function

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26.1 Tissue and Cell Types

1. The tissues of a flowering plant are meristems, ground tissue, dermal tissue, and vascular tissue, which includes phloem and xylem. The plant body consists of a shoot and a root. 
2. Meristems are localized collections of cells that divide throughout the life of the plant. Apical meristems located at the plant's tips provide primary growth, and lateral meristems add girth, or secondary growth.Essential Study Partner
Art Activity
Primary Meristems
3. Most of the primary plant body is ground tissue. It includes parenchyma cells, which can divide and store substances. A chlorenchyma cell is a type of parenchyma cell that photosynthesizes. Collenchyma supports growing shoots and sclerenchyma supports plant parts that are no longer growing. Sclerenchyma includes sclereids, which form hard coverings, and fibers, which form strands.Essential Study Partner
Ground Tissue
4. Dermal tissue includes the epidermis, a single cell layer covering the plant. The epidermis secretes a waxy cuticle that coats aerial plant parts. Gas and water exchange occur through epidermal pores (stomata), which are bounded by guard cells. Trichomes are epidermal outgrowths, and include root hairs.Essential Study Partner
Dermal Tissue
5. Vascular tissue is specialized conducting tissue. Xylem transports water and dissolved minerals from roots upwards. Xylem cells are elongated with thick walls and are dead. They include the long, narrow, less-specialized tracheids and the more specialized, barrel-shaped vessel elements.Essential Study Partner
Vascular Tissue
6. Phloem is a living tissue that transports dissolved carbohydrates and other substances throughout a plant. It includes sieve cells and, in flowering plants, the more specialized sieve tube members. Pores of sieve tube member cells cluster at sieve plates, allowing nutrient transport between adjacent cells via cytoplasmic strands. Companion cells help transfer carbohydrates. 

26.2 Anatomy of a Plant

7. A stem is the central axis of the shoot and consists of nodes, where leaves attach, and internodes between leaves, where the stem elongates. The apical meristem at the shoot apex produces cells that become dermal tissue and leaves. Vascular bundles in the stem contain xylem and phloem, which are scattered in monocots and form a ring in dicots. Between a stem's epidermis and vascular tissue lies the cortex, made of ground tissue. Pith is ground tissue in the center of a stem. Stem modifications include stolons, thorns, succulent stems, tendrils, and tubers.Art Activity
Organization of the Plant Body
Art Activity
Stem Tip
Art Activity
Dicot Stem Anatomy
Essential Study Partner
8. Simple leaves have undivided blades, and compound leaves form leaflets, which may be pinnate (with a central axis) or palmate (extend from a common point). Leaves are the sites of photosynthesis.Essential Study Partner
9. Leaf epidermis is tightly packed, transparent, and mostly nonphotosynthetic. Veins may be in either netted or parallel formation. Leaf ground tissue includes palisade and spongy mesophyll cells.Art Activity
Leaf Anatomy
Art Activity
Leaf Structure
10. Leaf modifications include tendrils, spines, bracts, storage leaves, insect-trapping leaves, and cotyledons.Art Quiz
Abscission Zone
11. Leaves are shed from an abscission zone in response to environmental cues. 
12. Roots absorb water and dissolved minerals. Taproot systems have a large, persistent major root, whereas fibrous root systems are shallow, branched, and shorter-lived. A root cap protects the tip of a growing root. The apical meristem produces cells that differentiate into the root's epidermis, cortex, and vascular tissues.Art Activity
Dicot Root Tip
Essential Study Partner
13. The root cortex consists of storage parenchyma and endodermis. Some roots are specialized for storage or adapted to low-oxygen environments. 

26.3 Secondary Plant Growth

14. Secondary tissues increase the girth of stems and roots.Animation
Secondary Growth
Art Activity
Secondary Growth in a Stem
15. Two lateral meristems, the vascular cambium and cork cambium, produce outward growth. The vascular cambium produces secondary xylem and secondary phloem. The cork cambium produces cork and other tissues that, along with secondary phloem, comprise bark. Older trees often have multiple cork cambia, producing a thick outer bark.Essential Study Partner
Art Activity
Woody Dicot Stem

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