AQA BIOL2~3rd June 2013~AS Biology (Now Closed) Watch
i'll have a shot, but i can't say it will be perfect:
- ions actively transported into xylem by endodermis
- this lowers the water potential of the xylem, causing water to move in by osmosis
- continuous column of water up the xylem
- hydrogen bonds between the water molecules give them cohesive properties
- this creates tension in the xylem
- adhesion of water molecules and xylem wall also aids transpiration
and good luck to everyone
I still don't understand it
- Large proteins remain in capillaries, reducing water potential of capillaries
- Loss of tissue fluid from capillaries reduces hydrostatic pressure
- Water returns to capillaries down a water potential gradient
- By osmosis
- The remainder of the tissue fluid is returned to the circulatory system by the lymphatic system.
So plant cannot photosynthesis (make its own food souce/engery)
as photosynthesis requires C02 So plant dies
- Increases diffusion pathway
- Rolling up of leaves
- Traps humid layer of air
- Reduces water potential grad, so less transpiration
- Hairy leaves
- Traps moist layer of air next to leaf surface, lowers water potential grad
- Stomata in pits and grooves
- Trap moist air next to leaf surface, reduces water potential grad
- Reduced SA/vol ratio
- Slower rate of diffusion
And also can anyone briefly explain to me differences between cohesion tension and root pressure? All help is appreciated
(Tissue fluid is blood plasma without any large proteins or red blood cells, and is found in the tissues)
The cells use nutrients from the tissue fluid in respiration.
The vein end of the capillary has a low pressure and a low water potential due to the large proteins that remain in the capillary.
Tissue fluid/water containing oxygen and carbon dioxide re-enter the capillary via osmosis.
Lymphatic vessels drain excess tissue fluid.
- thick waxy cuticle
- increases diffusion pathway
- rolling up of leaves
- traps humid layer of air
- reduces water potential grad, so less transpiration
- hairy leaves
- traps moist layer of air next to leaf surface, lowers water potential grad
- stomata in pits and grooves
- trap moist air next to leaf surface, reduces water potential grad
- reduced sa/vol ratio
- slower rate of diffusion
Water, ions and small molecules are filtered out of the blood into the spaces between cell - this is tissue fluid.
the loss of fluid from the blood leads to a fallin hydrostatic pressure as he look approaches the venue end of the capillary.
at the venue end of the capillary, the inward osmotic pull now exceeds the outward hydrostatic pressure and some of the water re enters by osmosis down a water potential gradient.
tissue fluid is drained away from the. Cells by the lymph vessels and returned to the circulation near the heart.
thats everything you need to know.