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Chapter 23

Chapter 23. Roots, Stems , and Leaves. The main organs of plants are roots , stems , and leaves. All plant organs are made of several types of tissue. a. Dermal – outer covering of plant i . Made of epidermal cells and a thick waxy covering called cuticle

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Chapter 23

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  1. Chapter 23 Roots, Stems, and Leaves

  2. The main organs of plants are roots, stems, and leaves. • All plant organs are made of several types of tissue. a. Dermal – outercovering of plant i. Made of epidermal cells and a thick waxy covering called cuticle ii. Considered the “skin” of the plant

  3. b. Vascular – internal system of interconnected tubes and vessels that is the transportsystem that moves water and nutrients throughout the plant i. Considered the “bloodstream” of the plant 1. Xylem – made of tracheids and vessel elements - moves water - tracheids are pierced with openings called pits that allow water to move from tracheid to tracheid

  4. 2. Phloem – made of connected sievetube cells • moves sugars and foods

  5. C. Ground - tissue that lies between dermal tissue and vascular tissue i. Considered “everythingelse”

  6. Meristems – clusters of tissue that continue growing throughout the plant’s life a. Meristems are the only plant tissue that produces cells by mitosis b. Apical meristem – located at the tip of each growing shoot and root

  7. Roots a. 2 types of roots i. Taproot – one large central root - mostly in dicot plants - Ex. carrot

  8. ii. Fibrous - many thin, shallow roots - mostly in monocot plants - Ex: grasses

  9. Root functions • Absorb water and dissolved nutrients • Anchor plants in ground • Hold plants upright against wind and rain

  10. Root structures i. Root hairs – help increase surfacearea to absorb more water ii. Root cap – protects apical meristem near root tip

  11. Stems • Functions of stems i. Produce leaves,branches, and flowers ii. Hold leaves up to sunlight iii. Transports substances between roots and leaves

  12. Primary growth i. Produced by cell divisions in apicalmeristem of all seed plants

  13. Secondary growth • Occurs in 2 types of tissue • Vascular cambium – produces vascular tissue (xylem and phloem) and stem thickness • Cork cambium – produces outer covering of stems (bark)

  14. Leaves a. Flat structure of leaf is optimized for absorbing light and carrying out photosynthesis

  15. Leaf Tissues i. Mesophyll – ground tissue that makes up most of the leaf 1. Palisademesophyll a. Located just under epidermis b. Absorbs light for photosynthesis

  16. 2. spongy mesophyll a. Contains airspaces that connect with stomata and guard cells in epidermis b. Stoma (stomata) - openings in leaf that allow gasexchange - regulates/prevents water loss for plant

  17. c. Guard cells - epidermal cells found on undersides of leaves - control opening and closing of stomata due to water pressure

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