Introduction

In last week's laboratory exercise you examined plant pigments and the external structure of leaves and stems of flowering plants, and plant growth and development. In today's exercise you investigate some properties of solutes and their influence of living cells, the root system, and interal organization of roots, stems and leaves.

I have tried to provide links to illustrations and descriptions of plant structures similar to those you will examine and to information that can help you understand the exercises you perform on water, solutes, diffusion, osmosis and plasmolysis.


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Solutes and Osmosis

 

General


     The following links lead to useful explanations of water, solutes, and movement in and out of cells.
 

• Transport in and out of cells
• Osmosis  definitions and descriptions
• Diffusion and osmosis
• Diffusion and Osmosis
• Plants and Water Botany Website at Kean

 

Plasmolysis

   You will observe plasmolysis in cells of

. Although the following links demonstrate plasmolysis in other cells, the process is similar.
 


Rheo leaves

Snap and peel the lower epidermis

• Plasmolysis - images including Rhoeo discolor-  with Potassium Rhodanite

 
• Plasmolysis onion movie - with audio shows plasmolysis and deplasmolysis
• Plasmolysed and normal cells onion
• Plasmolysis - scroll down to image of Elodea in sea water
• Plasmolysis - images and description - about 1/3 way down page
• plasmolysis - images Elodea and onion

Diffusion

   You will measure and compare the rate of diffusion of solutes moving in agar, a colloid.
The following links describe factors influencing the rate of diffusion and provide values.
 


Press dram vial into agar	Remove agar plugs
Add Ferrous sulfate to one well  and K ferricyanide to the other	Appearance of Prussian blue

 
• rate of diffusion

 

Turgor

   You will place cylinders extracted from potato tubers into water and into 10% solution of NaCl and measure the turgor (firmness) of the tissue. If water enters, the potato will become
firm. If water leaves, the potato will become flaccid (limp). The direction of movement will be determined by the amount of solute in the cells of the potato and in the solution outside.
The following links demonstrate the borer used to cut the cylinders of potato.
 


Use cork borer to obtain cylinder  of tissue from potato tuber

Expel cylinder of potato

Cylinders of potato    in water and NaCl

 

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Root Tip (External Views)




Radish seedling

• Root tip Grass seedling root
• Root hairs
• Root cap
• Pea root - region of elongation - growth marked with ink
• mitosis links

Internal Structure -- Anatomy

 

 
 
 
 
 
 
 


You will examine four slides.  1) Monocot and Dicot Root  2. Monocot and Dicot Stem  3. Monocot and Dicot Leaf 4. Woody stem

Roots

• root - U. Wisconsin

 
• Monocot Root
• Corn root - U. Wisconsin
• Dicot Root
• Ranunculus root x.s.

 
• More Roots Kean University - Botany Web Site

Stems

• Monocot Stems
• Corn Stem -
• Corn Stem - diagram and images at several magnifications
• Dicot Stems (herbaceous)
• Sunflower x.s. stem
• Sunflower x.s. stem (high power)
• Sunflower vascular bundle (stem) - labels
• More Stems Kean University - Botany Web Site
• Plant Tissue Systems
• Dicot Stems (woody)
• Tilia stem -  Tilia
• More Woody stems Kean University - Botany Web Site
• Plant Tissues and cell types

Leaves

• Dicot Leaves
• Lilac leaf -  U. Wisconsin
• Internal structure Dicot leaf diagram & photo (x.s.)
• More Leaves Kean University - Botany Web Site

 

 
 
 
 
 
 
 
 
 
 
 

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General Links

Botany Botany Website at Kean

Plants and Water Botany Website at Kean

Transport in and out of cells

Plant Tissues and cell types

Plant Tissue Systems


 

 
 
 
 
 
 
 
 

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Questions

 How do branches and growing regions of roots compare with those of shoots?

Hint: Consider and contrast the functions that roots and stems perform, the environment in which they perform the functions, and the adaptations that allow them to perform the function well. Also, consider what structures branches originate from in stems and in roots.

What morphological and anatomical characteristics can you use to distinguish roots from stems from leaves? Dicots from monocots?

 
Hint: Consider which tissues are present, the arrangement  of tissues, and the appearance of the organs as seen in thin sections and presence of stomates, root hairs, etc.

 

Can you explain the role of turgor and osmosis in plant growth and movement?

 
Hint: Consider what happens in the region of elongation;   how plants appear when they are badly in need of water, and the mechanism by which a Venus Fly Trap catches insects.

 

Can you explain why too much salt or too much fertilizer will burn or kill vegetation?

 

Hint: Think of what happened when you applied solutes (salt to tissue of potato and sugar to tissue of Rheo).

 

Not all woody plants produce annual rings. Can you think of reasons why not?

 

Hint: Try to think of environmental conditions that might not result in the change from large cells to small cells during a growing season.

 

6. What other information (besides age) is recorded in tree rings?

 

Hint: Consider what it is that causes the cells of wood to be large in spring wood and small in summer wood. Consider also other trees and other organisms (including humans, plant pests and disease causing organisms) and environmental factors ( including lightening, floods ) might impact trees.

 

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Assignment

Check with your own instructor to learn the assignment for your section. The instructions here apply to students in sections  taught by Dr. Reid.
1. Do the exercise as written. Record all observations and label the diagrams as directed in lab exercise 6.

 
2. Color the figures in the lab manual using the following color coding:

       red       -- xylem
       blue      -- phloem
       green   -- mesophyll
       orange -- endodermis
       violet   -- cortex  pith
       uncolored = white -- epidermis, pericycle
 
 
3. Prepare for a lab quiz next week.

 
Be able to distinguish sections of root from stem from leaf, and monocot from dicot. Be
able to identify tissues (epidermis, cortex, pith, xylem, phloem, endodermis, pericycle, mesophyll) as well as structures such as root cap, root hair, starch grains and stomates.