water transport question

Plants!

Moderators: honeev, Leonid, amiradm, BioTeam

Post Reply
Rigel
Garter
Garter
Posts: 6
Joined: Fri Jun 23, 2006 5:39 am

water transport question

Post by Rigel » Fri Sep 01, 2006 7:33 am

I have a few questions about plants' uptake of water. Is it true that during daytime when the plant is photosynthesizing, the xylem transports water up to the leaves all day long? And is it true that during night time, when the plant starts transpiration, its leaves lose water to the atmosphere, and creates more tension which causes the uptake of water during night time?
If i cut off the plant's root and leave it to transpire, can it still transport water up using the sucking force of leaves?

User avatar
fluktuacia
Death Adder
Death Adder
Posts: 75
Joined: Thu Jul 06, 2006 4:57 pm

Post by fluktuacia » Fri Sep 01, 2006 8:46 am

The transpiration occurs during the whole day, it depends mostly just on how widely the stomata are opened. I think that the whole transport of water up the plant is dependent prevailingly on the transpiration..

User avatar
Poison
Inland Taipan
Inland Taipan
Posts: 2322
Joined: Sun Jan 02, 2005 12:44 pm
Location: Turkey

Re: water transport question

Post by Poison » Fri Sep 01, 2006 5:18 pm

Rigel wrote:If i cut off the plant's root and leave it to transpire, can it still transport water up using the sucking force of leaves?


Yes. That's why you put flowers to a vase full of water.
You can try it with a simple experiment. You've probably heard of it. Ink experiment. Get a white flower (without roots), place it in water and drop blue (or red, you chose) ink to the water. After approximately 1-2 days if you cut the stem you can see the ink has moved up, and your white flower has some blue spots on it.
It matters not how strait the gate
How charged with punishment the scroll
I am the Master of my fate
I am the Captain of my soul.

User avatar
MrMistery
Inland Taipan
Inland Taipan
Posts: 6832
Joined: Thu Mar 03, 2005 10:18 pm
Location: Romania(small and unimportant country)
Contact:

Post by MrMistery » Fri Sep 01, 2006 5:34 pm

and by the way, since the plant uses only about 1% of the water it transports, photosynthesis has nothing to do with water transport. neither does respiration. the main thing that influences it is transpiration.
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter

Rigel
Garter
Garter
Posts: 6
Joined: Fri Jun 23, 2006 5:39 am

icic

Post by Rigel » Fri Sep 01, 2006 6:39 pm

Ok i get it, so transpiration occurs all the time right?
thanks guys

User avatar
fluktuacia
Death Adder
Death Adder
Posts: 75
Joined: Thu Jul 06, 2006 4:57 pm

Post by fluktuacia » Fri Sep 01, 2006 7:55 pm

yes you're right, it does.

User avatar
MrMistery
Inland Taipan
Inland Taipan
Posts: 6832
Joined: Thu Mar 03, 2005 10:18 pm
Location: Romania(small and unimportant country)
Contact:

Post by MrMistery » Sat Sep 02, 2006 5:31 pm

Not quite. Most plants close their stomas at night and stop transpiration. This is because the guard cells have a blue light receptor called zeaxantin. This molecule activates a proton pump that excrets protons from the cell. this creates a difference in the electrical potential of the cell that opens some potassium channels in the cell membrane. Potassium rushes into the cell, but then the tables turn: there is an excess of positive ions inside the cell. The cell copes with this by accepting some chloride ions and breaking down starch into malate ions. So what does this have to do with transpiration? Well, all those ions lower the water potential of the cell, and water rushes into the cell, making it turgid. Due to the well-advertised difference in thickness of the guard cell walls, the stoma opens.

Now, during nightime, there is no light so none of these happens, so there is no transpiration. Be aware that this mechanism can be overridden by some plants(CAM plants are a notable example, that open their stomas at night) both to keep stomas closed during the day and to open them at night.

Does this sound scary and complicated? That's ok, only a total geek like me knows stuff like this. Memorise this and then tell it to your teacher. You'll get an A for sure ;)
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter

Rigel
Garter
Garter
Posts: 6
Joined: Fri Jun 23, 2006 5:39 am

Post by Rigel » Sun Sep 03, 2006 5:02 pm

oh WOOW never knew transpiration can get that complicated. If i do my experiment on this, i'm sure i'll have lots to write about!
THANKS A LOT!

beluga fiction
Garter
Garter
Posts: 23
Joined: Fri Apr 07, 2006 1:46 pm

Post by beluga fiction » Mon Sep 04, 2006 11:05 am

What about marine and fresh water plants?
Tell us more Mr. Cheese.

Post Reply

Who is online

Users browsing this forum: No registered users and 2 guests