CHAPTERS 31 + 32
CHAPTERS 31 + 32. Plant Structure and Function. 31.3 Three Basic Parts of a Plant: Roots, Stems, and Leaves. Roots. Anchors the plant in the soil Absorbs an transports minerals and water Stores food. Stem. Above the ground Supports and separates the leaves Flowers for reproduction
CHAPTERS 31 + 32
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Presentation Transcript
CHAPTERS 31 + 32 Plant Structure and Function
Roots • Anchors the plant in the soil • Absorbs an transports minerals and water • Stores food
Stem • Above the ground • Supports and separates the leaves • Flowers for reproduction • Leaves for photosynthesis
Leaf -“the blade” -Usually flat to receive sunlight -Veins contain water and food-conducting tubes
Some Leaf Vocabulary • Parenchyma = non-woody, functioning part of the plant • Chlorenchyma= photosynthesizing non-woody, functioning part of the plant
Leaf • Blade = usually the flat, broad organ above ground – the leaf • Midrib= central or main vein
Xylem Tissue • Contains two water-conducting cells: • Dead, only cell walls • Water moves only up the plant.
Phloem • Food conducting tubes (up and down) • Cells remain alive
Transpiration • Evaporation of water from mostly leaves (could also be stems). • Transpiration You Tube
How does the water get from the roots to the leaves? • 1. Root pressure – water absorbed in roots • 2. Mass flow of liquid water from the roots to the leaves is driven in part by capillary actionup the xylem tubes. • 3. Transpiration evaporation pulls the water up.
Capillary Action in Xylem • Adhesion of water to sides of xylem tubes (hydrophilic cellulose molecules via H-bonds) and cohesion of water to water molecules (H-bonds) to make a column.
Transpiration Pulling force of water by evaporation Guard cells control transpiration.
How Guard Cells Work • A stoma opens when its guard cells gain K+ ions and water by osmosis • The water vacuoles become turgid and the guard cells become bowed (inner membrane is thicker) as they fill and open the stoma
How the Guard Cells Work (2) • When the guard cells lose K+, they also lose water by osmosis • The water vacuoles become flaccid and less bowed • The stomata close
Usually • Guard cells keep stomata open during the day • CO2 enters for photosynthesis • Guard cells keep stomata closed at night • No sunlight-no photosynthesis-save water
3 clues to stomatal opening at dawn • 1. SUNLIGHT-stimulates guard cells to accumulate K+ • 2. LOW LEVEL OF CO2 in the leaf • 3. BIOLOGICAL CLOCK of some sort (even if put in a dark closet, they will still open)
If it is a drought, WHAT HAPPENS? • The stomata will close to reduce water loss and prevent wilting. This also slows down CO2 intake and photosynthesis.
Root Pressure Pushes water up xylem a few meters
Leaf Texture • Waxy Hairy • Rough
