Biology of Plants
Spring 1994

Exam II

Name_________________

This take home exam is due at 4 PM on Friday, March 18, 1994. [note: in the printed version, questions appeared on a separate pages marked here with a horizontal rule]

Meristem Analysis:

The table below shows the number of cells counted in a single microscopic field of view at low power of particular 1-mm segments of an onion root tip longitudinal section.
SegmentInterphaseProphaseMetaphaseAnaphaseTelophaseSum PMAT
A500202315 
B250153215 
C503000 
D400000 

Complete the table and analyze completely the results in the space below.


Starting a Fantastic Voyage in Plant Anatomy!

You are trying to find out how ions make their way through a plant. You have developed a new technology to shrink yourself to a very tiny size. To avoid being lost, you have developed a backpack to attach yourself to a magnesium ion (Mg2+) Your lab partner puts you (piggy-backed to the Mg2+ ion) into the soil of a potted plant in the lab. Write the pathway your Mg2+ "ship" travels. Be sure to list each cell encountered in sequence and anything special happening to your ship along the way until it becomes hopelessly trapped in the plant. [Conclusion on next page]


Concluding Our Fantastic Voyage!

Your lab partner is planning to recover you in root exudate and hoping you made a "round trip." Tell how you will get out of the plant. Hint: your backpack is physically attached to an electron of the Mg2+ ion and some of this answer is a review! Remember the Mg2+ is hopelessly trapped!


Secondary Growth:

When a fusiform initial divides in the ____________________ plane another fusiform initial is formed.

Why does the plant need a new fusiform initial?

 

 

 

When a fusiform initial divides in the ____________________ plane a (group of) ray initial is formed.

What is the function of a ray initial and its cellular products?

 

 

 

Why would a plant need to make more ray initials (Hint: doesn't it already have enough ray initials in the cambium?)?

 

 

 

The chemical produced in abundance by cambium initials is ___________________.

When a fusiform initial divides in the ____________________ plane a derivative is made.

If the inner cell matures the derivative becomes a cell of the _______________ tissue.
A chemical produced in abundance by this derivative is ___________________.
If the outer cell matures, the derivative becomes a cell of the _______________ tissue.
A chemical produced in abundance by this derivative is ___________________.
If we turn our attention to the cork cambium, all the initials are the same because they have the same dimensions. Why does the cork cambium not need special ray initials?

 

 

 

When a cork cambium initial divides in the ____________________ plane a derivative is made.

If the outer cell matures, the derivative becomes a cell of the _______________.
A chemical produced in abundance by this derivative is ___________________.
If the inner cell matures, the derivative becomes a cell of the _______________. Why is this derivative not sclerenchyma?


A Potential Problem?

A uniseriate (one cell wide) filament of Polysiphonia (a microscopic alga) finds itself at low tide. The filament has four cells and the lower cell is immersed in the ocean (-25 bars solute potential). The other end is sticking up into the atmosphere (-225 bars solute potential). The side-walls of the filament of cells are coated with a water-resistant polysaccharide matrix...the end-walls of the cells are not coated and water exchange is likely at these end-walls. Initially all of the cells are turgid and have -60 bars of matric potential (these algae also produce a polysaccharide gel inside) and -20 bars of solute potential. Tell how water flows, what happens in each cell in terms of the components of water potential as the situation stabilizes during low tide.

The problem is best visualized sideways: [better in printed version too: walls can be distinguished in the original, Y is printed as the Greek letter psi, and the cells are all the same size. Netscape does not respond to the Colspec and Math html commands so this is not possible to render properly on your WWW browser, sorry.]

Sea Water

 
Ys = -25
Yp =
Ym =
Y=
Cell 1Cell 2Cell 3Cell 4
Atmosphere

 
Ys = -225
Yp =
Ym =
Y=
water-proofpolysaccharidematrix
Ys =
Yp =
Ym =
Y=
Ys =
Yp =
Ym =
Y=
Ys =
Yp =
Ym =
Y=
Ys =
Yp =
Ym =
Y=
water-proofpolysaccharidematrix

List the assumptions you have made in coming up with your solution.

 

 

 

 

 

 

 

 

Peel Me A Grape!

There are many ways that a plant stem is mechanically supported in the air. Start by sprouting a seed from a grape. List what supports the stem as it grows.


Mystery Plant!

As an anthropologist you have just unearthed some seeds in a dig site. One is dated by 14C analysis and found to be 7500 years old. Another seed is dissected and found to contain a single seed leaf. The seeds are clearly not viable. Predict what the plant's anatomy must have been like so the museum curator can make a diorama. Be sure to tell about root, stem, and leaf and be complete in your description...a table might be the best way to do that consistently.

 

 

 

 

 

 

 

 

 

 

 

Leaf Me Alone!

On the rest of this page list some adaptations of leaves. You might want to organize your list.


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