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AP Biology 2006-2007 Transport in Plants AP Biology Transport in plants 1. H 2 O & minerals transport in xylem transpiration Water potential, adhesion.

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Presentation on theme: "AP Biology 2006-2007 Transport in Plants AP Biology Transport in plants 1. H 2 O & minerals transport in xylem transpiration Water potential, adhesion."— Presentation transcript:

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2 AP Biology Transport in Plants

3 AP Biology Transport in plants 1. H 2 O & minerals transport in xylem transpiration Water potential, adhesion & cohesion 2. Sugars transport in phloem bulk flow Photosynthesis in leaves loads sucrose into phloem 3. Gas exchange photosynthesis CO 2 in; O 2 out stomata respiration O 2 in; CO 2 out roots exchange gases within air spaces in soil

4 AP Biology Overview Sugars travel from leaves to roots through phloem Water and dissolved minerals travel from root to shoot through xylem It defies gravity! h?v=w6f2BiFiXiM

5 AP Biology 1. Transport of Water and Minerals Amount of water needed daily by plants is small compared to the amount that is lost through transpiration Transpiration: evaporation of water from plant surface If water is not replaced, the plant will wilt and may die.

6 AP Biology Water Potential Water movement is governed by differences in water potential The potential energy of water molecules Solute concentration and pressure Water moves from an area of higher water potential to lower water potential High solute concentration = low water potential Low solute concentration – high water potential PE High Water Potential Low Water Potential Hydrostatic pressure causes water to travel up tube

7 AP Biology The Process - Roots Minerals from the soil Actively transported into the root hairs and start to accumulate Increase solute concentration in root cells, decrease water potential Water moves in through osmosis to xylem cells High Water Potential Low Water Potential WATER H2OH2O root hair

8 AP Biology As water enters the xylem, it forces fluid up the xylem due to hydrostatic root pressure positive pressure This pressure can only move fluid a short distance. The most significant force moving the water and dissolved minerals in the xylem The pull of water from transpiration cohesion & adhesion Hydrostatic pressure causes water to travel up xylem Pull = Negative Pressure

9 AP Biology Adhesion and Cohesion H2OH2O – O H H + + Water is a polar molecule unequal sharing of electrons in the covalent bonds oxygen atom has a stronger attraction for electrons then hydrogen O becomes slightly negatively charged H becomes slightly positively charged

10 AP Biology Cohesion and Adhesion Water molecules are attracted to one another and other materials Cohesion Due to: Hydrogen Bonds Force of attraction between slightly – oxygen and slightly + hydrogen of adjacent water molecules Adhesion Attraction between water molecules and the side of xylem cells

11 AP Biology Transpirational Pull Starts in Leaves Evaporation of water through stomata Lowers WP in the surrounding air spaces Water moves from spongy cells (higher WP) to air spaces (lower WP) Water in spongy cells exerts a pull on column of water molecules in the xylem all the way from the leaves to the roots (adhesion, cohesion)

12 AP Biology HIGH water potential LOW water potential

13 AP Biology Mycorrhizae increase absorption Symbiotic relationship between fungi & plant symbiotic fungi greatly increases surface area for absorption of water & minerals increases volume of soil reached by plant increases transport of minerals to host plant

14 AP Biology Mycorrhizae

15 AP Biology 2. Transport of Sugars C 6 H 12 O 6 Photosynthesis: CO 2 + H 2 O C 6 H 12 O 6 + O 2 Storage form of sugar: Starch Cannot be transported, must be broken down into smaller components Transport form of sugar: Sucrose Very sweet sap Usable form of sugar: Glucose

16 AP Biology Push and Pull Water and minerals are mainly transported via transpiration negative pressure or pull Sucrose is mainly transported via: positive pressure (hydrostatic pressure) push force (+) pressure due to accumulati on of water pull force (-) pressure due to adhesion & cohesion

17 AP Biology Companion cells Cells that surround phloem Contain a lot of mitochondria Why? A lot of active transport! ATP

18 AP Biology can flow 1m/hr Transport of Sugars Mass flow hypothesis source to sink flow Source = leaf, Sink = root Phloem loading in leaf active transport of sucrose into phloem increased sucrose concentration decreases water potential Water flows in from xylem cells increase in pressure due to increase in water causes flow Hydrostatic pressure ATP

19 AP Biology Phloem unloading into root cells active transport of sucrose into root cells Decreases pressure in bottom of plant Sucrose will travel from high pressure near leaves to low pressure near roots ATP

20 AP Biology What environmental conditions might impact transpiration of water? 3. Gas Exchange

21 AP Biology Chloroplasts Epidermal cell Nucleus Guard cell Thickened inner cell wall (rigid) Stoma openStoma closed H2OH2O water moves into guard cells H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O Gas Exchange Regulation water moves out of guard cells In dry conditions water leaves guard cells by osmosis guard cells become flaccid stomata close to prevent water loss In humid conditions water enters guard cells by osmosis guard cells become turgid stomata open to facilitate water flow

22 AP Biology Control of transpiration Balancing stomate function always a compromise between photosynthesis & transpiration leaf may transpire more than its weight in water in a day…this loss must be balanced with plants need for CO 2 for photosynthesis

23 AP Biology Dont get mad… Get answers!! Ask Questions!

24 AP Biology Homework Section 9.5 – pg. 326 #1-9 Read Transpiration Lab


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