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Plant NotesPlant NotesRoots, Stems, and LeavesRoots, Stems, and Leaves
qwetqwetChapter 23Chapter 23
Roots, Stems, and LeavesRoots, Stems, and Leaves
• Three of the principal organs of seed Three of the principal organs of seed plants are roots, stems. and leavesplants are roots, stems. and leaves..
Function in:Function in:1. Transport
2. Protection
3. Coordination of plant activities
Plant Tissue SystemsPlant Tissue Systems
Plants consist of Plants consist of threethree
main tissue systemsmain tissue systems::1. Dermal tissue
2. Vascular tissue
3. Ground tissue
Dermal TissueDermal Tissue
• The “skin” of a plantThe “skin” of a plant• Contains a waxy Contains a waxy
cuticlecuticle to prevent to prevent water losswater loss
Vascular TissueVascular Tissue• Plants “bloodstream”Plants “bloodstream”• Transports water and nutrients throughout the Transports water and nutrients throughout the
plant.plant.• Made of Made of XylemXylem and and PhloemPhloem
PhloemXylem Phloem
XylemXylem
• Water conducting Water conducting tissuetissue
PhloemPhloem
• Food conducting tissueFood conducting tissue. .
RootsRoots
Two main types:Two main types:
1.1. TaprootsTaproots – found mainly in dicots – found mainly in dicots
2.2. Fibrous rootsFibrous roots found mainly in monocotsfound mainly in monocots
Root Structure and GrowthRoot Structure and Growth• The root’s surface is The root’s surface is
covered with cellular covered with cellular projections called projections called root hairsroot hairs. . Root Root hairs provide a large hairs provide a large surface area through surface area through which water can which water can enter the plantenter the plant..
Root hairs
Root FunctionRoot Function
• Anchor a plantAnchor a plant• Absorb waterAbsorb water• Absorb dissolved nutrientsAbsorb dissolved nutrients
Stems- FunctionsStems- Functions
• Produce leaves, branches and Produce leaves, branches and flowersflowers
• Hold leaves up in the sunlightHold leaves up in the sunlight
• Transport various substances Transport various substances between roots and leavesbetween roots and leaves
Copyright Pearson Prentice Hall
Monocot and Dicot StemsMonocot and Dicot Stems
•Monocot and Dicot StemsMonocot and Dicot Stems–The arrangement of tissues in a stem differs among seed plants.–How do monocot and dicot stems differ?
Copyright Pearson Prentice Hall
Monocot and Dicot StemsMonocot and Dicot Stems• Monocot Stems
• Vascular bundles are scattered throughout the ground tissue.
Monocot
Vascular bundles
Epidermis
Ground tissue
Copyright Pearson Prentice Hall
Monocot and Dicot StemsMonocot and Dicot Stems
–Dicot Stems• Dicot stems have
vascular bundles arranged in a ring-like pattern.
Dicot
Cortex
Pith
Vascular bundles Epidermis
LeavesLeaves
• The structure of a leaf is optimized for absorbing light and carrying out photosynthesis.
Leaf FunctionsLeaf Functions•The air spaces connect with the exterior The air spaces connect with the exterior through stomata.through stomata.
•Stomata are porelike openings in the underside Stomata are porelike openings in the underside of the leaf that allow carbon dioxide and oxygen of the leaf that allow carbon dioxide and oxygen to diffuse into and out of the leafto diffuse into and out of the leaf..
Stoma
Copyright Pearson Prentice Hall
Leaf FunctionsLeaf Functions•Each stoma consists Each stoma consists of two guard cells.of two guard cells.
•Guard cells are Guard cells are specialized cells that specialized cells that control the opening control the opening and closing of stomata and closing of stomata by responding to by responding to changes in water changes in water pressure.pressure. Guard cells
Copyright Pearson Prentice Hall
Leaf FunctionsLeaf Functions
•When water pressure within guard cells is When water pressure within guard cells is high, the stoma open.high, the stoma open.
Copyright Pearson Prentice Hall
Leaf FunctionsLeaf Functions
•When water pressure within guard cells When water pressure within guard cells decreases, the stoma closes.decreases, the stoma closes.
Copyright Pearson Prentice Hall
Leaf FunctionsLeaf Functions
•Plants regulate the opening and closing of Plants regulate the opening and closing of their stomata to balance water loss with their stomata to balance water loss with rates of photosynthesis.rates of photosynthesis.
•Stomata are open in daytime, when Stomata are open in daytime, when photosynthesis is active, and closed at night, photosynthesis is active, and closed at night, to prevent water loss. to prevent water loss.
•In hot, dry conditions stomata may close In hot, dry conditions stomata may close even in bright sunlight, to conserve water.even in bright sunlight, to conserve water.