Help on Plant Science - Botany

xBobbyCx · Post by **xBobbyCx** » Sat Apr 22, 2006 1:09 am

Hi,

I'm doing a project on plant tissues, where I have to label pictures. I have some questions, would really appreciate any help given

1. Is an adventitious root the same as a root hair? Why?

[I think it is, as they do not have a tap root - main root - growing from stems or places where roots do not generally appear, right?]

2. Is 'stele' the same as 'vascular cylinder'?

[I noticed that stele includes phloem, xylem, pericycle and endodermis. Vascular cyclinder includes xylem, phloem, pith, pericycle and endodermis. So are they the same?]

3. Casparian strips prevent water leaking from the plant? They are part of the endodermis, do they face the exterior ( meaning plant cortex ), or do they face the interior ( pericycle )?

4. I've been searching the internet, but there are a few different labels for the part of the leaf near the shoot apical meristem. The names are periderm, procambium and leaf primordia/primordium. Pls help me with the differentiation.

PS: the internet gives me many different answers and I don't know which is reliable. I search by google search engine.

Pls help me

Thank you!!

Lise Byrd · Post by **Lise Byrd** » Sat Apr 22, 2006 7:33 pm

Plant anatomy can be difficult because the differences between parts that look the same can be subtle.

1. Adventitious roots are not the same thing as root hairs. The root hairs are exactly what they sound like-- "hairs" growing on the root. You can see them if you pull a carrot or a radish out of the ground. Adventitious roots are a network of fibrous roots and are only found in monocots such as corn and mangroves. Adventitious roots derive from the shoot system and not the root system.

2. Stele is not a term I have seen before, but from what I can tell, it is the arrangement of the vascular tissues at the center of the vascular cylinder.

3. The Casparian strip does prevent water leakage from the roots. It is wrapped lengthwise along each cell in the endodermis, so water can only flow through the cells, not between them. The Casparian strip is found between the pericycle and the cortex and is parallel to both. There is a reasonably good visual (it shows only the endodermis) at http://faculty.clintoncc.suny.edu/facul ... ucture.htm

4. Periderm is the scientific name for bark; procambium is a meristem that produces vascular tissue; the leaf primordia is the developing leaf at the top of the plant. So all three can be found near the shoot meristem.

Here are a couple more websites that are very accurate and may help you with other terms:
http://www.uri.edu/artsci/bio/plant_ana ... ssary.html
http://waynesword.palomar.edu/trjune99.htm

Good luck with your diagrams!
Sonia

xBobbyCx · Post by **xBobbyCx** » Sat Apr 22, 2006 10:52 pm

Hi Sonia,

thanks for your help!

But I think adventitious root does not always derive from shoot system as sometimes can be found in other places like the leaf or flower petal, right?

I have found an image regarding stele : http://facweb.furman.edu/~lthompson/bgy ... t_root.htm
it's the last image in this web. Does it look like vascular cylinder to you?

Oh btw does vascular bundle consist of bundle sheath and the latter group mentioned, or just the xylem + phloem + cambium (separating the x and the p) ?

PS: regarding the Casparian strip picture, I'm very confused now cos my teacher once drew an image on the board about the strip which totally looks different from the one in ur url. But I have no idea how to post it on this site for you to take a look.

Thanks,
Bobby

xBobbyCx · Post by **xBobbyCx** » Sat Apr 22, 2006 11:00 pm

Sorry for posting a new reply but there was no 'edit' button for me to add on.

I took this off the internet:

Pericycle

The pericycle is the layer just inside the endodermis.

It retains the capacity to divide and form branch roots.

Can we also say it has capacity to form lateral roots? Are branch and lateral roots the same

Lise Byrd · Post by **Lise Byrd** » Sun Apr 23, 2006 11:51 am

Bobby,

As far as I know adventitious roots grow from the base of the stem; I have not found references to their growing near leaves or flowers.

From the picture you gave me, yes, the stele does look like the vascular cylinder.

A vascular bundle consists only of xylem, phloem, and cambium. The different arrangements of vascular bundles in the roots and stems differentiate monocots from dicots.

Branch and lateral roots are the same thing.

The image I gave you for the Casparian strip is not the best one, but it was the best one I could find. See if this helps you: The first image shows a single endodermal cell with the Casparian strip around it. In front of this cell would be a pericycle cell, and behind it would be a cortex cell. The second image shows what the endoderm would look like if you sliced it lengthwise; the dots between the cells are the Casparian strip. Water moves from the cortex, through the endoderm, into the pericycle. The third image is the same cross-section, but without the Casparian strip. Water can flow between the endodermal cells and even cross from endodermal cell to endodermal cell. (This is prevented by the Casparian strip.) So it becomes much more difficult to get all the water into the root.

Let me know if you're still confused, and I'll see if I can find a better image.

Sonia

Lise Byrd · Post by **Lise Byrd** » Sun Apr 23, 2006 11:57 am

Here is an image more like what I was looking for to show the Casparian strip:
http://www.hcs.ohio-state.edu/mgonline/ ... 1pla01.htm

The red lines between the endodermal cells are the Casparian strip. The strip would also extend above and below the cells in the picture, but would not be on the sides that face the cortex and the pericycle.

Sonia

xBobbyCx · Post by **xBobbyCx** » Tue Apr 25, 2006 6:40 am

The picture below was given by my teacher, showing a single endodermis cell. There are many side by side. But it looks so different from the pictures you provided me. Furthermore, you said

The Casparian strip does prevent water leakage from the roots. It is wrapped lengthwise along each cell in the endodermis, so water can only flow through the cells, not between them. Water can flow between the endodermal cells and even cross from endodermal cell to endodermal cell. (This is prevented by the Casparian strip.)

I'm so sorry, but does it mean water doesn't move between endodermal cell and cortex cell, but only through the endodermis meaning endodermal to endodermal? but if the strip is between each endodermal cell, then the water cannot pass through easily.

cortex here

___________________________
l l l l
l l l l
l l l l
l l l l another endodermal cell here
l l l l
l l l l
l l_________________l l
l casparian strip l
l__________________________l

pericycle here [/quote]

xBobbyCx · Post by **xBobbyCx** » Tue Apr 25, 2006 6:43 am

erm. seems like the picture doesn't work.

Ok.. the picture given looks like this.. I think have to rely on ur imagination..

Imagine a glass (without handles) and u see it sideways. The glass is the casparian strip and the air contained by the glass is sth else. but the entire thing, the glass and the air contained, is one single endodermal cell. and there are many cells lined on the side of the 'glass'.

Can you get what I'm trying to describe?

Lise Byrd · Post by **Lise Byrd** » Tue Apr 25, 2006 7:46 pm

Yes, I understand perfectly what you're trying to say.

I must have mistyped something in my last reply. Water cannot flow between endodermal cells. It flows from the cortex, through one endodermal cell, into the pericyle. For a visual: Take the glass cup you described to me. Imagine cutting the bottom off the cup so you have a hollow tube. On one open end is a cortex cell, on the other open end is a pericycle cell. Around the actual glass on the outside are other similar cups-- other endodermal cells. Water will flow through any of the hollows (if we're imagining multiple cups), but the actual glass (the Casparian strip) around the "cell" prevents it from going in between endodermal cells or from endodermal cell to endodermal cell.

I hope this helps you. Your confusion seems to be partly my mistake, so I'm very sorry for that.

Sonia

xBobbyCx · Post by **xBobbyCx** » Wed Apr 26, 2006 3:34 am

Hi Sonia,

I get it now - how the strip looks like. You know, now I'm confused about another thing. [The Casparian strip does prevent water leakage from the roots.] Umm if water flows from cortex through endodermal cell then to pericycle, how does that prevent water leakage from the roots?

Lise Byrd · Post by **Lise Byrd** » Thu Apr 27, 2006 6:57 am

The Casparian strip regulates the amount of water that enters the roots, since all of the water has to go through the endodermal cells. The strip also prevents water leakage because the water has fewer places to leak out of, and it is hindered by water entering the cells.