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

[Sue T]

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
n By the way i dunno tht hydrogen ions thingi cn u xplain more pls?

[Wahab09]

Sure
Whats water?
H2O right?
The hydrogens are bonded with the oxygen. So the hydrogen ions in the H2O will move up (as it is lighter than the O2) so it will automatically drag the oxygen with it.
I dno if that makes any sense to you
But thats the way.
Here it is in definition terms:
Transpiration creates a pulling force which pulls a continuous unbroken column of water up the xylem vessels. The water molecules are held together by forces of attraction. This creates a water potential gradient through the plant.

 

[SGVaibhav]

i understood capillary action.

sweetsh
page 10
explain the mechanism of water uptake and
movement in terms of transpiration producing a
tension ('pull') from above, creating a water
potential gradient in the xylem, drawing
cohesive water molecules up the plant.

hmm
can anyone explain me cohesion and adhesion, and wat is pits in xylem

it would be good if someone has a summary of the whole topic.

[Wahab09]

sgvaibhav
Non of the terms you mentioned you need to know for the Cambridge IGCSE exam this June. Trust me you just need to know how and stuff and i think Sue T and I have explained it clearly.

[sweetsh]

Yes exactly as Wahab said....Those terms are not included...

But you should know how the water moves along the plant from the roots till leaving the leaf by the affect of transpiration....

I will explain you whats meant by pits and everything about the xylem vessels after 3 hours if you can wait =)

[SGVaibhav]

lol i can
haha



i have one sort of textbook (not exactly textbook, someone prepared this book)
it is quite inaccurate and wrong at times also.
but the good thing about it that it is more like a summary, that helps in revision.
should i scan and attach those 2 to 3 pages? (but i cant gurantee if the content is right)

[sweetsh]

No need ...wait for me about 3 hours from now...

And I'll tell you the name of my book as it is amazing concluding everything you need

[SGVaibhav]

which book do u have?

[emi]

as i know ,, the thing i posted is the only thing thats coming ,,
those things are not in the syllabus .


not in my textbooks neither my guides .

[sweetsh]

Sorry but I was studying chemistry....

OKay now...
My book is Complete Biology for IGCSE by Ron Pickering...
http://www.worldcat.org/oclc/162144426

About the transpiration thing...let me explain it in simple words...
First thing...you have to know how the uptake of water and minerals occur in roots...They enter root hair cells by osmosis...As the water in the soil has a high water potential gradient than the cytoplasm of the root hair cell...Thats how the water enters...  Then,,,water crosses the living cells of the cortex by osmosis...It crosses the cell wall and cytoplasm of the endodermis...The cell wall of the endodermis contains a waxy material which makes them impermiable to water...So the membranes of endodermis cells select what sybstances can enter the xylem and to be distributed through the body of the plant...

Now part(2)...Transport in plants  You know that inside the plants there xylem tissue and phloem tissue...
Xylem tissue contains xylem vessels...to transport water and dissolved mineral ions...
Its walls are thickened by LIGNIN...its waterproof and prevent the cells collapsing inwards...
There is no cytoplasm or organelles inside..(which is a kind of adaptation) so there will be no obstruction to the flow of water and mineral ions...
NOW...the end walls are removed...cells join to form long hollow tunes calles xylem vessels...
**They have small holes in their sides called pits..When the water from the root hair cell arrive in the center of the root it goes into the xylem vessels through there pits...

Well the picture in mybook is very useful and I cant find a good picture to make you understand!!

Third thing...Phloem tissue...it contains sieve tubes and companion cells...Its adapted for transport of the organic products of photosynthesis(sugars as sucrose) and amino acids...This is called Translocation
Translocation is the movement of sugars and amino acids from source(where they were made)to the sink(where they are stored or used)
They have think cytoplasm-cell must remain alive or sugar transport stops..
There is no nucleus or organelles..so sugar flow is not impeded...
Pores in sieve plates allows sugars to pass from one cell to the next...
Companion cells doesnt transport sugars but carries out some life processes of the sieve tubes..... !!!

Now a little bit explanation about transpiration because im sure you got bored or maybe slept on the keyboard!!!
Transpiration stream is the flow of water through the plant to replace the losses by evaporation from the leaf...
As the water loss occur from the leaves...this reduces the pressure at the tops of the xylem vessels by transpiration.It becomes less than the pressure of the base,thats why water moves upwards..
1)Water uptake occur by osmosis(as I mentioned above)
2)water moves  up the stem in the xylem due to the tension caused by water loss from the leaves.
3)water moves from xylem to enter the leaf tissue down the water potential in the leaf tissues///
4)water evaporates into internal air spaces from the surfaces of leaf cells
5)water diffuses through stomata dow water potential gradient....

You may also know the leaf structure and how its adapted to reduce transpiration...

And the atmospheric conditions that affect transpiration...I think those are included in your textbooks and can be easily understood...

Dont forget how some plants are adapted to reduce water loss in diff. environments...(such as cacti,aquatic plants, and maram grass)

I hope I benefited you from this huge article!!! But I really wish you understand!!
Note: I attached a silly photo which shows transpiration very simply just to help you in studying...

Good Luck for you and Me...
sweetsh

[ashgerrard]

WOW
I reallly liked that!
I didnt understand the transpiration and transport of water until I read your post thanks
 

[sweetsh]

You welcome..!! 

Well I didnt understand them for the first time..But after reading these things I became used to it...

But I really advise you to buy that book...Its amazing...From amazon or something..

P.s I tried to make it attractive by adding colours Haha!!

Enjoy studying...

[emi]

thanks nice ,, but
i didnt get this part
"They have think cytoplasm-cell must remain alive or sugar transport stops..
There is no nucleus or organelles..so sugar flow is not impeded...
Pores in sieve plates allows sugars to pass from one cell to the next...
Companion cells doesnt transport sugars but carries out some life processes of the sieve tubes..... !!!"

wat do u mean by the must remain alive .. ? 

[sweetsh]

The cells inside this tissue must remain ALIVE not like the xylem...Because sugar wont be transported ...

They dont ask you about details more than that dont worry

[SGVaibhav]

thanx for all those huge articles
i now understand how it all happens
:D
thanx man
the diag made me laugh, it was funny
hehe

this is ur 99th post, one more reach 100
happy 100th post