Office Hours Fri Feb 7 526 12 20 1 10 pm Wed Feb 12 526 12 20 1 10 pm Fri Feb 14 412 2 30 3 30 pm Today How are plants different from animals fundamentally Animals circulatory system pumped osmosis Transport in plants Diamorpha 1 inch Dolystrichem 1 inch Helianthus porteri 3 ft Ferns 1 ft Redwood sequoia 379 ft tallest Osmosis is involved vascular tissue used in long distance Challenges Water take up enough to support transpiration while maintaining turgor in living cells o Transpiration water evaporation out of leaves o turgor only happens with cells that have cell walls Nutrient take up enough and distribute where needed o Sugar transport both ways to wherever it is needed o To roots that are growing or to leaves that are developing Photosynthetic products carbs move from where produced or stored to where needed Focus on What is being moved Scale and location of movement o Short across membranes o Longer vascular tissue phloem xylem How s it being moved o Diffusion o Osmosis o Bulk flow Outline over next two lectures Water movement across cell membranes o Osmosis o Water potentials o Turgor pressure Water and nutrient acquisition by roots Transpiration and xylem transport Phloem transport Today Hypotonic solution solution has lower solute concentration than inside the cell why water moves in Animal cell Cell could lyse explode Plant cell Turgid normal dynamic equillibrium Isotonic solute concentrations are equal in solution to inside the cell Normal Plant cell flaccid no turgor Hypertonic solution has higher solute concentration than inside the cell why water leaves the cell Cell shrivels Plasmolyzed Clicker Main feature that makes substantial turgor possible in living plant cells A vacuole B cell membrane C cell wall D chloroplasts E chlorophyll Vacuole is not substantial enough How can plant cell water exchange be in equilibrium if solution is hypotonic to the cell Explains how solute concentration is not the only reason for water exchange in plant cells Net transport processes Diffusion movement of substance down concentration electrochemical gradient driving force Osmosis diffusion of water across a selectively permeable membrane where physical property that predicts direction of water is water potential o Better definition movement of water across a cell membrane down a water potential gradient Process water movement across membranes Transport process osmosis Driving force water potential gradient units MPa Rules for predicting how water will move across living cell membranes When crossing one or more cell membranes water moves from areas of higher potential to areas of lower potential until equilibrium Potential made of 2 components potential potential solute pressure potential o increasing solutes in water lowers s gets more negative o Pressure increases p positive and tensions decreases negative pressure potential Living plant cells are osmometers with relatively rigid cell walls that can build up torgor positive p Putting numbers on s p for plant cells Exercise in class what happens when an individual plant cell is put into one of the solutions below assume cell wall rigid and that cell cytoplasm volume doesn t change Initial flaccid cell p 0 s 0 7 MPa 0 7 MPa 0 4 M sucrose solution water moving out by osmosis o Solution p 0 s 0 9 0 9 o Plasmolyzed cell at equilibrium with surroundings p 0 s 0 9 0 9 Distilled water o solution p 0 s 0 0 o Turgid cell p 0 7 s 0 7 0 o At equilibrium 0 Question for studying later what would happen if a flaccid cell with a s of 1 0 is put into the distilled water and the 0 4 M sucrose solution or into a 0 8 M sucrose solution Clicker In order to maintain water uptake