Qualification > Sciences

IGCSE BIOLOGY------>TRANSPORT IN PLANTS

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emi:
i see  :D

astarmathsandphysics:
This new breed of cows cum humans, being able to more efficiently convert grass into poo than the grass-cow-human-poo cycle we have now, will be better able to exploit the earths resources. The new cow-cum-human super race, able to run faster, jump higher, eat more, will out compete both humans and cows until they are no more. And because their stomachs are hidden in their bums, everyone will think they are just very fast, very fat people.

SGVaibhav:
i thought that was u saifalan

K_M:
Hey i have a doubt.

Active Uptake is the movement of molecule of a substance against their concentration gradient (from lower concentration to high concentration). But how it is applicable to the absorption of mineral ions from the soil by the roots. Because obviously the soil has more mineral ions than the root.

Please explain this to me asap. I think ive misunderstood the concept.

ambitious94:

--- Quote from: Sue T on April 11, 2009, 03:39:31 pm ---Whoever asked the xylem thingi question im gonna xplain in my own words
Imagine sipping juice through a straw. The straw is really thin so the water rises through it easily-imagine sippin the juice through a pipe. Its hard ryt? So that’s pretty much capillary action, which is weak - u see xylem vessels r thin so water rises up against gravity easily.
Now in the root cells, thers pressure due 2 accumulation of water. This forces water out of one cell and into the other so they reach the xylem vessels. That’s root pressure or turger pressure but its also a weak pressure. Now @ th top, in the leaves, water is being lost due 2 transpiration. They are fewer water particles up here and more down the xylem vessels so as u no in osmosis water particles move from a region of high water potential to lower water potential n the water potential gradient is created due 2 all these thingis.Voila!water moves up :p
Hope u understand :D
n By the way i dunno tht hydrogen ions thingi cn u xplain more pls?

--- End quote ---
Ur explanation is rlly good, except for the part where water moves up by osmosis. That's an incorrect statement, because osmosis is the movement of water particles from a region of higher concentration to a region of lower concentration through a partially permeable membrane there fore, the transpiration stream is not caused by osmosis, but due to the fact that water molecules are attracted to each other, so when they escape by transpiration, water is pulled up the xylem vessels. This was in my study guide. :)

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