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Plant Systems Part II

Plant Systems Part II. Plant Tissues. A tissue is a group of cells working together to perform a similar function. The cells in tissues are specialized to perform specific functions. All these cells develop from unspecialized cells during cellular differentiation

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Plant Systems Part II

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  1. Plant Systems Part II

  2. Plant Tissues • Atissueis a group of cells working together to perform a similar function. • The cells in tissues are specialized to perform specific functions. • All these cells develop from unspecialized cells during cellular differentiation Recall: what were unspecialized cells called in animals? Stem Cells! • In plants, these cells are not called stem cells – they are called meristematic cells • A region of a plant that is rich in meristematic cells is called the meristem region (see video on plant growth and meristematic cells)

  3. Tissue Systems • Plants have 3 major tissue systems: • Dermal • Covers outer surface of plant • Vascular • Found in every root, shoot and leaf • System is continuous (all plant parts joined by vascular tissues) • Ground • All other tissues

  4. Dermal Tissue System

  5. Dermal Tissue System Cells of the Dermal tissue system: • Epidermal root cells have extensions (root hairs) to absorb water and minerals • Epidermal leaf cells produce a layer of wax to waterproof surface • Some have developed for defense purposes

  6. Vascular Tissue System • This is the transportation system that moves water, minerals and other chemicals around the plant • All vascular tissues are connected

  7. Vascular Tissue System

  8. Vascular Tissue System Xylem • Transports water and dissolved minerals upwards from the roots • Cells are hollow tubes with rigid walls • No cytoplasm, nucleus or organelles (allows for easier transportation of water) • MATURE xylem cells are not considered living tissue

  9. Vascular Tissue System Phloem • Transports sugars produced by photosynthesis (and hormones) • Phloem can move sugars downwardsfrom the leaves and stems or upwardsfrom the roots • Phloem cells are alive when functioning

  10. Ground Tissue System • The ‘filler’ between dermal and vascular tissues • Functions: • In green parts of plant, they manufacture nutrients via photosynthesis • In stems, they provide storage and support • In roots, they storecarbohydrates

  11. Photosynthesis – Tissues Working Together • Because sugar (glucose) is so important to all components of a plant, it must have a system in place to transport the sugars • Oxygen is also required by plant cells (for cellular respiration) • Leaves produce more O2 than is needed, and any excess is released as waste

  12. Recall: Plants and Food • Since plants cannot move like animals do to obtain food, they must make their own food through a process called photosynthesis. light energy + carbon dioxide + water  glucose + oxygen glucose

  13. Photosynthesis – Absorbing Light light energy + carbon dioxide + water  glucose + oxygen • Leaves that are wide and thin are ideal for light absorption. Why? • Greater SA Remember: Photosynthesis occurs in chloroplasts

  14. Photosynthesis – Absorbing Light • Chloroplasts are contained in the mesophyll layers • Palisade mesophyll is located where there is maximum light • Spongy mesophyll is located throughout leaf with air pockets in between • Mesophyll layers as a whole are part of ground tissue system

  15. Photosynthesis – Obtaining CO2 • CO2 will naturally diffuse into a leaf. To avoid too much diffusion, the leaf is coated with a layer of epidermal tissue called the cuticle • Gases enter and exit through openings in the leaf called stomata • Stomata are controlled by guard cells.

  16. Photosynthesis – Obtaining Water • Leaves will close their stomata when water levels are low • Leaves obtain water through vascular tissues (xylem and phloem) • Arranged as bundles called vascular bundlesand run from root to leaf • Root hairs (epidermal) grow into soil from roots and obtain water via diffusion • Water is transferred via xylem, from the roots to the leaves

  17. What is a tissue? • Name the three tissue types in plants and briefly describe their function. • What is the difference between dermal and periderm tissues? • Describe the difference between the xylem and phloem. • What is the difference between the spongy and palisade mesophyll? • How does the shape of a leaf help photosynthesis take place? • What is a stomata? How do the guard cells open and close?

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