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Chapter 23 Plant Structure and Function

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1 Chapter 23 Plant Structure and Function
Tissue systems and growing regions Roots Stems Leaves

2 Tissue Systems Ground system Vascular system Dermal tissue system

3 Vascular and Dermal Systems
Xylem conducts water and minerals Phloem conducts food Dermal Epidermis: outer layer of cells

4 Ground System Parenchyma tissue: food storage
Collenchyma tissue: growing regions of the plant Sclerenchyma: at maturity is made of dead cells that support and strengthen the plant Ground System

5 Meristems: growing regions where cells divide
Apical Meristem: the tips of stems and roots (result of primary growth) Lateral meristem: the circumference grows (result of secondary growth) Cork cambium and vascular cambium Herbaceous Plants have no vascular cambium so are nonwoody Woody Plants are perennial (adapted for growth year after year) so they produce secondary xylem.

6 Roots: Structure Root tip – 3 regions
Region of cell division Region of elongation Region of maturation Root cap: composed of cells that protect the apical meristem

7 Roots: primary growth Root hairs increase surface area for absorption
Cortex: storage tissue for the young root Vascular cylinder: contains xylem and phloem

8 Roots: secondary growth
Occurs when a vascular cambium forms between the primary xylem and phloem. Provides strength and support for the plant stem.

9 Roots: Functions Absorption of water and inorganic nutrients
The amount of water absorbed depends on the amount lost through transpiration which is the evaporation of water from stems and leaves. Food storage Anchors the plant

10 Stems: Structure Primary Growth
Stems only grow at the apical meristem Dermal tissue protects the stem Ground tissue forms a cortex and a pith (in gymnosperms and dicots) Vascular bundles: xylem and phloem Monocots: bundles are scattered throughout ground tissue Dicots: bundles occur in a single ring

11 Stems: secondary growth
Stems increase in thickness due to cell division in the vascular cambium (production of more secondary xylem is wood). Rays are sheets of cells that radiate from the stem center storing food and transporting water laterally across the xylem Annual rings develop because of water differences among seasons Bark is the outer layers that protect a plant and consists of cork, cork cambium, cortex and secondary phloem.

12 Secondary Growth in Stem

13 Stems: Functions Support Food Transport: Water Transport: Storage
Food: sugar moves from source to sink Pressure-flow hypothesis (diffusion) explains this Water Transport: Transpiration-cohesion theory – osmosis and cohesion Storage Photosynthesis

14 Leaves: Structure Leaves are the result of only primary growth
Parts: blade and petiole

15 Leaves: internal structure
Epidermis: impermeable layer that only allows water, oxygen and carbon dioxide to pass Mesophyll: chloroplast-rich parenchyma cells Palisade mesophyll lies directly below the epidermis Spongy mesophyll lies between the palisade and lower epidermis Vascular tissue is contained in veins surrounded by bundle sheaths.

16 Leaf cross section:

17 Leaves: Functions Capturing light Gas exchange:
Guard cells surrounding openings called stomata Opening and closing regulated by turgor pressure 1)When guard cells have water – guard cells expand and create a pore 2) When guard cells have lost water, they shrink and close the pore


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