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November 6th Lecture

November 6th Lecture - Transport in plants Water potential...

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Transport in plants Water potential. – potential energy of water (ability to do work) Positive pressure , zero pressure or negative pressure when you blow in a straw you get a pos. pressure, suck up it’s negative and nothing is zero. Solute pressure- (harder to get through a crowd if there are a lot of people) same effect that solute has on water, (solute lowers water potential) Water moves from high potential energy to lower potential (you put pressure in water in some place, you has higher water potential and goes to another spot with lower pressure) How? You can induce pressure by adding solutes or [you can suck it up (xylem)] Osmosis - diffusion of water across a semi-permeable membrane in response to a difference in water potential [ this occurs one molecule ar a time,] always involved living membranes. All based only on a concentration gradient, and this can be created by making sugars in one place over another. Water moves through pipes like it does in plants In vessels. More particles means the lower the free energy of water (water potential). A polymer of thousands of glucose molecules is also considered a (just like meat attracts a dog, water would is attracted to solutes and particles, when there are more particles in one place than another, than it means that the water is going to diffuse into that area) Particles move around through active transport and then water would follow. Movement through plant membranes is in the combination of diffusion and mass low. Gravity has a big role in water movement too.. Remember that water has cohesion. (sticky) Hydrogen ends become positively charged while the oxygen become negatively charged, so that each oxygen gets attracted to the other hydrogens in the water and then formed like a connection. Weak hydrogen bond. (you know when suck out a little bit of water the other parts of the water seems to follow) A Guard Cell (day time by the wat), it creates an opening where the co2 can come in and water can enter and leave. The subsidiary cells are there too. The guard cells open because of increased turgor pressure from osmosis. Bulk Flow is not involved. In order to get the guard cell to open, it uses transport mechanisms to move the solutes into the stomata and then the water follows and the guard cell swell and the stomata
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opens. IN the night, the entire process reverses, the solutes leave the stomata and the water follows, it shrinks and closes up. WATER IS MOVED WITH NO ENERGY.. BUT ATP IS USED TO MOVE THE SOLUTES. How does osmosis and mass flow interact in an osmotetor. Osmometer – there is a high concentration of sugar at the soure, the water would flow in And at the sink, the other end, the sugar concentration is lower, so the water would leave.
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