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Plant Tissues

Plant Tissues. Chapter 26. Success of the Angiosperms. The angiosperms are seed-bearing vascular plants In terms of distribution and diversity, they are the most successful plants on Earth The structure and function of this plant group help explain its success. Plant Life Histories.

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Plant Tissues

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  1. Plant Tissues Chapter 26

  2. Success of the Angiosperms • The angiosperms are seed-bearing vascular plants • In terms of distribution and diversity, they are the most successful plants on Earth • The structure and function of this plant group help explain its success

  3. Plant Life Histories • Annuals complete life cycle in one growing season • Biennials live for two seasons; flowers form in second season • Perennials grow and produce seeds year after year

  4. Shoots and Roots • Shoots • Produce food by photosynthesis • Carry out reproductive functions • Roots • Anchor the plant • Penetrate the soil and absorb water and dissolved minerals • Store food

  5. Angiosperm Body Plan EPIDERMIS • Ground tissue system • Vascular tissue system • Dermal tissue system VASCULAR TISSUES GROUND TISSUES SHOOT SYSTEM ROOT SYSTEM

  6. Meristems • Regions where cell divisions produce plant growth • Apical meristems • Lengthen stems and roots • Responsible for primary growth • Lateral meristems • Increase width of stems • Responsible for secondary growth

  7. Apical Meristems • Lengthen shoots and roots • Cells that form at apical meristems • Protoderm • Ground meristem • Procambium activity at meristems new cells elongate and start to differentiate into primary tissues

  8. Lateral Meristems • Increases girth of older roots and stems • Cylindrical arrays of cells vascular cambium cork cambium thickening

  9. Complex Tissues Composed of a mix of cell types Xylem Phloem Epidermis

  10. Xylem • Conducts water and dissolved minerals • Conducting cells are dead and hollow at maturity vessel member tracheids

  11. Phloem: A Complex Vascular Tissue • Transports sugars • Main conducting cells are sieve-tube members • Companion cells assist in the loading of sugars sieve plate sieve-tube member companion cell

  12. Monocots and Dicots: 1 cotyledon 2 cotyledons 4 or 5 floral parts 3 floral parts Netlike veins Parallel veins 3 pores 1 pore Vascular bundles dispersed Vascular bundles in ring

  13. Shoot Development shoot apical meristem protoderm procambrium ground meristem cortex procambrium pith primary xylem primary phloem

  14. Internal Structure of a Dicot Stem • Outermost layer is epidermis • Cortex lies beneath epidermis • Ring of vascular bundles separates the cortex from the pith • The pith lies in the center of the stem

  15. Internal Structure of a Monocot Stem • The vascular bundles are distributed throughout the ground tissue • No division of ground tissue into cortex and pith

  16. Leaf Gross Structure DICOT MONOCOT petiole axillary bud blade node sheath blade node

  17. Adapted for Photosynthesis • Leaves are usually thin • High surface area-to-volume ratio • Promotes diffusion of carbon dioxide in, oxygen out • Leaves are arranged to capture sunlight • Are held perpendicular to rays of sun • Arrange so they don’t shade one another

  18. Leaf Structure UPPER EPIDERMIS cuticle PALISADE MESOPHYLL xylem SPONGY MESOPHYLL phloem LOWER EPIDERMIS CO2 one stoma O2

  19. Mesophyll:Photosynthetic Tissue • Cells have chloroplasts • Two layers in dicots • Palisade mesophyll • Spongy mesophyll

  20. Leaf Veins: Vascular Bundles • Xylem and phloem; often strengthened with fibers • In dicots, veins are netlike • In monocots, they are parallel

  21. Root Systems

  22. Root Structure • Root cap covers tip • Apical meristem produces the cap • Cell divisions at the apical meristem cause the root to lengthen • Farther up, cells differentiate and mature

  23. Root Hairs and Lateral Roots • Both increase the surface area of a root system • Root hairs are tiny extensions of epidermal cells • Lateral roots arise from the pericycle and must push through the cortex and epidermis to reach the soil new lateral root

  24. Secondary Growth • Occurs in all gymnosperms, some monocots, and many dicots • A ring of vascular cambium produces secondary xylem and phloem • Wood is the accumulation of these secondary tissues, especially xylem

  25. Secondary Growth

  26. Woody Stem periderm (consists of cork, cork cambium, and secondary cortex) secondary phloem HEARTWOOD SAPWOOD BARK vascular cambium

  27. Annual Rings • Concentric rings of secondary xylem • Alternating bands of early and late wood • Early wood • Xylem cells with large diameter, thin walls • Late wood • Xylem cells with smaller diameter, thicker walls

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