Chlorophyll+Flourescenece,+Water+Movement,+and+Stomata+Counting+Lab

As water evaporates from the leaves of a plant, more water is drawn up by osmosis from the tissues below to replace it. The replacement of water lost through transpiration is possible because water molecules have polar covalent bonds. This causes one end of the molecule to have a slightly positive charge and the other end to have a negative charge. Because of this, the water molecules act like "small magnets". The positive end of one water molecule sticks to the negative end of another in a long chain that is pulled upward against the force of gravity. When enclosed in a narrow tube, such as the transport vessels of a plant, water molecules can withstand a large force without being pulled apart. 1. Fill the beaker with **100 mL** of distilled water. Add drops of food coloring, stirring with the stirring rod, until the water is colored. Set this aside. 2. Cut off the bottom two centimeters of the celery stalk. 3. Quickly place the freshly cut celery stalk upright in the beaker of colored water. Record the beginning time on your **DATA TABLE** 4. Allow the celery to remain in the food coloring until the color is visible in the upper stem and leaves. Record the ending time on your **DATA TABLE**, and remove from the beaker of food coloring. 5. Measure the length the color traveled up the celery stalk in centimeters. Record on your **DATA TABLE** ** Beginning time: _ __ Ending time: ___ Length food color traveled up stalk. __**cm**__ 6. Calculate the number of minutes it took for the coloring to reach the top. __ Time for color to reach the top of stalk. = ___ __**minutes**__ 7. Calculate the **rate of travel** of the food coloring up the celery stalk in **centimeters per minute**. ** time for color to reach top of stalk (min) ** ||
 * **// Water Transport in Plant Stems //** ||  ||
 * INTRODUCTION: **
 * MATERIALS NEEDED: **
 * Celery stalk with leaves intact || || Metric ruler ||
 * 400-mL beaker || || Water ||
 * || || Food coloring ||
 * Scissors || || Stirring rod ||
 * PROCEDURE: **
 * DATA TABLE:
 * CALCULATIONS: **
 * ** Rate of Travel ** || ** = ** || ** length of celery stalk (cm) **

__** Rate of travel = **_____ cm / min
 * QUESTIONS: **
 * 1. What type of tissue moves water upward in a plant stem? **


 * 2. Name and explain 2 properties of water that enable it to move upward against gravity in a stem. **


 * 3. What is transpiration and where does it occur in plants? **


 * 4. How does transpiration help the upward movement of water? **

When a ** pigment ** absorbs light, electrons of certain atoms in the pigment molecules are boosted to a higher energy level. The energy of an absorbed ** photon ** is converted to the potential energy of the electron that has been raised to an ** excited state **. In most pigments, the excited electron drops back to its ground-state, or normal orbit, and releases the excess energy as heat. Some pigments, including ** chlorophyll **, emit light as well as heat after absorbing photons. In the ** chloroplast **, these excited electrons jump from the chlorophyll molecule to a protein molecule in the ** thylakoid ** membrane, and are replaced by electrons from the splitting of water. The energy thus transferred, is used in carbohydrate production. This release of light is called ** fluorescence **. Chlorophyll will fluoresce in the red part of the spectrum, and also give off heat. In this lab, you will observe this fluorescence by separating the chlorophyll from the thylakoid membrane. 1. Grind the spinach leaves using a mortar and pestle. 2. Add acetone to the ground leaves, using enough acetone and spinach leaves to get between **10** and **15 mL** of extract. 3. Set up your filtering apparatus, and filter the extract to a test tube. **NOTE:** You should not have any spinach debris in your test tube, only clear green liquid. 4. Shine a flashlight, or other similar light source, through the test tube and extract. 5. Observe the fluorescence of the chlorophyll at a **90 degree angle** to the flashlight. What accounts for the change in color of your extract?
 * **// Chlorophyll Fluorescence //** ||  ||
 * INTRODUCTION **
 * MATERIALS **
 * Spinach leaves || || Flashlight or small lab light ||
 * Mortar and pestle || || Test tube ||
 * Acetone || || Filter paper ||
 * 25-mL graduated cylinder || || Funnel ||
 * Ring stand or funnel rack || || ** Safety goggles ** ||
 * PROCEDURE **
 * Question: **
 * Counting Leaf Stomata ||   ||

Plants and animals both have a layer of tissue called the **epidermal layer**. Plants have special pores called stomata to allow passage of material. The **stomata** pores are surrounded on both sides by jellybean shaped cells called guard cells. Unlike other plant epidermal cells, the guard cells **contain chlorophyll** to do photosynthesis. This allows the cells to expand/ contract to open or close the stomata. Guard cells also close when dehydrated. This keeps water in the plant from escaping. The opening or closing of guard cells can be viewed in a microscope by adding different water concentration to the leaf tissue. Most stomata are on the **lower epidermis** of the leaves on plants (bottom of the leaf). The number of stomata on the epidermal surface can tell you a lot about a plant. Usually, a high concentration of stomata indicates fast growth and wet climate. Lower concentrations of stomata indicate lower rates of photosynthesis and growth or adaptations for dry weather. To view and compare the stomata from the leaves of several species of plant 3 leaves (1 from 3 different species), compound light microscope, 3 microscope slides, clear nail polish, transparent tape  1. Obtain three leaves from different types of plants.  2. Paint a thick patch (at least one square centimeter) of clear nail polish on the underside of the leaf surface being studied.  3. Allow the nail polish to dry completely.  4. Tape a piece of clear cellophane tape to the dried nail polish patch.  5. Gently peel the nail polish patch from the leaf by pulling on a corner of the tape and "peeling" the fingernail polish off the leaf. This is the leaf impression you will examine.  6. Tape your peeled impression to a very clean microscope slide. Use scissors to trim away any excess tape. Label the slide with plant name.  7. Examine the leaf impression under a light microscope at 400X.  8. Search for areas where there are numerous stomata, and where there are no dirt, thumb prints, damaged areas, or large leaf veins. Draw the leaf surface with stomata.  9. Count all the stomata in one microscopic field. Record the number on your data table.  10. Repeat counts for at least three other distinct microscopic fields. Record all the counts. Determine an average number per microscopic field.  11. From the average number/400X microscopic field, calculate the stomata per mm2 by multiplying by 8.  12. Follow procedures 2 - 11 with the other leaves. (with several stomata) ** ||  || || ||
 * // Introduction //**
 * // Purpose: //**
 * // Materials: //**
 * // Procedure: //**
 * // Data: //**
 * || ** Leaf 1 ** || ** Leaf 2 ** || ** Leaf 3 ** ||
 * ** Name of Leaf ** || || || ||
 * ** Drawing in 400x
 * ** Stomata in field 1 ** ||  ||   ||   ||
 * ** Stomata in field 2 ** ||  ||   ||   ||
 * ** Stomata in field 3 ** ||  ||   ||   ||
 * ** Average Stomata in field ** ||  ||   ||   ||
 * ** Stomata/ mm2 ** || || || ||

**// Conclusion: //** 1. Which leaf had the most stomata? Why do you think this was so?

2. Explain, in detail, how guard cells open and close stomata?

3. At what time of day would stomata be closed and why?

4. Why does the lower epidermis have more stomata than the upper epidermis of a leaf?

5. Define transpiration.

6. What two gases move in and out of the leaf stomata? 7. What does a larger number of leaf stomata indicate about the growing climate of that plant?

8. Would you expect CAM plants to have as many stomata? Why or why not?