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Plant Science

Plant Science. Topic 9. Plant Structure and Growth. Topic 9.1. Assessment Statements. Three Major Plant Groups - Review. Angiosperms Tissue Types. Meristematic Tissue Composed of aggregates of small cells (similar to stem cells)

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Plant Science

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  1. Plant Science Topic 9

  2. Plant Structure and Growth Topic 9.1

  3. Assessment Statements

  4. Three Major Plant Groups - Review

  5. Angiosperms Tissue Types • Meristematic Tissue • Composed of aggregates of small cells (similar to stem cells) • Meristematic cells differentiate into different tissue cells, such as: • Dermal tissue • This outer protective covering protects against physical agents and pathogenic organisms • It prevents water loss and may have specialized structures for various purposes • Ground tissue • Contains mostly of thin-walled cells that function in storage, photosynthesis, support and secretion • Vascular tissue • Xylem and phloem carry out long-distance conduction of water, minerals and nutrients within the plant and provide support

  6. Plant Organs • Roots • Function: • absorb mineral ions and water from soil • Anchor the plant • Provide food storage (in some cases) • Organization • Epidermis – protective outer layer • Cortex – involved in conducting water from the soil to the interior vascular tissue and may be modifies to carry out storage functions • Endodermis – surrounds the vascular tissue • Vascular tissue – includes the xylem and phloem • Conduct water, nutrients, and mineral ions around the plant

  7. Plant Organs

  8. Stem • Stem is the ‘trunk’ of the plant • Where the leaves attach = node • Area between two nodes = internode

  9. Stem http://www.ibguides.com/biology/notes/plant-structure-and-growth • Epidermis: protection • pores (lenticels): allow gas exchange • Transporting tissues • Xylem: carries water and dissolved minerals from roots to leaves • In woody plants, also provides support • Phloem: transports organic nutrients • Cambium: area of rapidly dividing cells that differentiate into xylem and phloem • Cortex: resembles that of a root • Supports and may have storage functions • Pith: storage and support area • Turgid, fluid filled cells offer support to the plant

  10. Leaf

  11. Leaf Tissues • Cuticle: protects against water loss and insect invasion • Vascular Bundle: • Xylem: bring water to the leaf • Phloem: takes the products of photosynthesis to plant • Palisade Mesophyll: cylindrical cells – contain chloroplasts that carry out photosynthesis • Spongy Mesophyll: loosely packed cells, air space provides gas exchange • Stomata: pores that allow oxygen and carbon dioxide exchange • Guard Cells: control the opening and closing of the stomata

  12. Leaf Functions Summary • Palisade Mesophyll is located in upper portion  where light is most available, chloroplast rich, allowing maximal photosynthesis • Veins distributed throughout leaf  transport raw materials and products from photosynthesis • Spongy mesophyll just superior to stomata allowing continuous channels for gas exchange • Stomata pores on bottom less light, lower temperature, minimizes water loss from pores

  13. Monocots vs. Dicots • Angiosperms • Specialized structures  flowers • Flowers coevolved with pollinators (insects, bats, and birds) • Animals transfer the male pollen to female reproductive portions of flowers -> fertilization and seed development occurs

  14. Monocots vs. Dicots

  15. Root Systems

  16. Root Modifications

  17. Stem Modifications

  18. Leaf Modifications

  19. Meristems • Indeterminate growth: show growth throughout life cycle • Determinate growth: cease growth after reaching certain size • Life cycle of plants: • Annuals: complete life cycle in one year • Biennials: complete life cycle in two years • Perennials: long life, death due to infection or environmental factor

  20. Meristems Apical Lateral aka: secondary growth Allow growth in thickness of plants Occurs in woody plants (trees and shrubs) Types of lateral meristems Vascular cambium – produces secondary vascular tissue Lies between the xylem and phloem Cork cambium – produces the cork cells Occurs within the bark • Aka: primary meristems • Occurs at the tips of roots and stems • Produces primary tissue and primary growth • Allows roots the extend through soil • Stem growth increases • Occurs in herbaceous, non-woody stems and roots

  21. Meristems

  22. Tropism • Tropisms • Growth or movement responses to directional external stimuli • Positive: towards stimulus • Negative: away from the stimulus • Types of stimuli • Chemicals, gravity, touch and light

  23. Phototropism's • Phototropism's • Stimulus of light • Stems exhibit positive phototropism • Roots exhibit negative phototropism • Importance: • Seedlings need to grow towards light in order to increase photosynthesis

  24. Auxins • Auxins • Plant hormone that causes positive phototropism of plant shoots and seedlings • Found in embryo of seeds, meristems of apical buds and young leaves • Only works with auxin receptors • Increase the flexibility of plant cell walls • Enables cell elongation of the side of shoot necessary to cause growth towards the light • Redistributed auxin to the stem side away from light source • Result: uneven auxin causes greater cell elongation on side away from light, causing curvature • Auxin responsible: indoleacetic acid (IAA)

  25. Auxins and Phototropism's

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