Chromatography of Plant Pigments Sample 2 PreAP

 

Chromatography of Plant  Pigments

 

Introduction

Chromatography is a way of separating a mixture using differences in the abilities of the components to move through a material. All chromatography involves two phases – a stationary phase and a mobile phase. The movement of the mobile phase through the stationary phase allows separation to take place. Because the components of a mixture move at different rates, they eventually separate.

Paper chromatography is a common way to separate various components of a mixture. The components of the mixture separate because different substances are selectively absorbed by paper due to differences in polarity. A solution can be separated by allowing it to flow along a stationary substance. Water or some other solvent is used as the mobile phase. The solvent moves upward along the paper because of capillary action. As it reaches the spot, the mixture dissolves in the solvent. For instance, the pigments in an ink solution can be separated by passing the ink through a piece of paper. The pigments respond differently to the paper. The differences in the migration rates result in differences in the distances the separated components travel, some pigments are held back while other moves ahead. Eventually, a pattern of colors results that shows the separated pigments.

Hypothesis

Paper can be used to separate mixed chemicals.

Materials

The materials used for this lab are paper, pencil, scissors, eraser, filter paper, test tube, cork, paper clip, metric ruler, black felt-tip pen, and a calculator.

Methods

The first step to this experiment was to bend a paper clip so that it is straight with a hook at one end. Push the straight end of the paper clip into the bottom of a cork stopper. Next, hang a thin strip of filter paper on the hooked end of the paper clip. Insert the paper strip into the test tube so it does not touch the sides, but almost the bottom of the test tube. Next, remove the paper strip from the test tube and draw a solid 5 mm wide band about 25 mm from the bottom of the paper, using a black felt tip pen. Use a pencil to draw a line across the top of the paper strip 10 cm from the top.

Pour about 2 mL of water into the test tube with the bottom of the paper in the water and the black band above the water. Observe what happens as the liquid travels up the paper. Record the changes you see. When the solvent has reached the pencil line, remove the paper from the test tube. Let the paper dry on the desk. With a metric ruler, measure the distances form the starting point to the top edge of each color. Record the data in a data table. Calculate a ration for each color by dividing the distance the color traveled by the distance the solvent traveled.

Results

The results of the experiment are shown in a chart and a graph.

Distance color traveled and Rf value.

 

Color of ink (list in order Distance traveled by each color (mm) Distance solvent traveled (mm) Ration traveled =
Distance color moved /Distance water moved
Yellow 50 120 5/12
Orange 85 120 17/24
Pink 100 120 5/6
Red 105 120 7/8
Blue 115 120 23/24
Violet 120 120 1

 

Questions

1. How many colors separated from the black ink? Six colors separated from the black ink: yellow, orange, pink, red, blue, violet.

2. What served as the solvent for the ink? Water served as the solvent because it is the universal solvent.

3. As the solvent travel up the paper, what color appeared first? Orange appeared first as the solvent traveled up the paper.

4. List the colors in order from top to bottom that separated from the black ink? The colors that separated from top to bottom: violet, blue, red, pink, orange, and yellow.

5. In millimeters, how far did the solvent travel. The solvent traveled 120mm.

6. From your results, what can you conclude is true about black ink. That black ink is a combination of several colors and that can be separated by water.

7. Why did the inks separate? The ink separated because each pigment has its own characteristics and molecular structure.

8. Why did some inks move a greater distance? Different pigments were absorbed at different rates.

Error analysis

There could be an error by the way the ink was distributed on the paper or by the amount of water put in the test tube.

Conclusion

The hypothesis was correct. This experiment showed the way black ink could be separated. Black ink is made from a various colors— yellow, orange, pink, red, blue, and violet. The colors separate because of the differences in their molecular characteristics, their solubility in water and their rate of absorption by the paper.

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Chromatography of Simulated Plant Pigments

 

Chromatography of Simulated Plant Pigments

 

Introduction
    This experiment is conducted to investigate the components Plant Pigments separating visibly. There are a couple of different types of components in plant pigments, and they became clearly visible during this lab. The most important and abundant chemical pigment found in plants is chlorophyll. This pigment exists in two forms; chlorophyll a and chlorophyll b. Chlorophyll absorbs two main colors from light quite well. These are blue, and red. The chlorophyll reflects green light very well, however, the two different types of chlorophyll have their maximum absorption at different wavelengths of light. Chlorophyll a, being the main photosynthetic pigment, has a primary purpose to convert light energy to chemical energy used by the plant itself. Chlorophyll b absorbs light in a region of the spectrum apart from the dominant chlorophyll, and transfers the energy it produces to chlorophyll a. Along with chlorophyll b in transferring their energy produced to the dominant chlorophyll, two other pigments that are found in plants are carotenes and xanthophylls, which are orange and yellow respectively. Since chlorophyll is such a dominant pigment in green plants, this domination hides the color of the carotenes and xanthophylls in the leaves. This causes most plant leaves to appear green most of the time. During the autumn, however, the chlorophyll starts to break down, causing the carotenes and xanthophylls to show their bright red, orange and yellow colors.
These brilliant colors can be separated another way. This different technique, known as paper chromatography, separates mixtures in a liquid into individual components. The technique is based on the fact that each substance in a mixture has a specific affinity for a solid surface and a specific solubility in different solvents. By this method, the solid surface is the cellulose fibers in the chromatography paper, and the solvent is the solution that was placed in the bottom of the developing chamber.
This separation takes place through a process of absorption and capillary action. Just a small drop of the mixture, in this case plant pigment to be separated, is placed at the bottom of the strip of chromatography paper. The chromatography paper is then placed in the developing chamber with a solvent, which wicks up the paper, pulling the solvent up the paper by capillary action, and the mixture of pigments is dissolved as the solvent passes over it. The different components of the mixture move upward at different rates. A compound with greater solubility will travel farther than one with less solubility. The pigments then show up as color streaks on the chromatography paper. These substances have formed a pattern called a chromatogram on the chromatography paper.
The Rf values for each pigment is calculated to establish the relative rate of migration for each pigment. This value represents the ratio of the distance a pigment traveled on the chromatogram relative to the distance the solvent front moved.
Scientists use the Rf value of a sample to identify the molecule. Any molecule in a given solvent matrix system has a uniquely consistent Rf value. The formula for this value is as follows:

Rf = Distance each pigment traveled ¸ Distance solvent front traveled

 

Hypothesis
    Using paper chromatography, the pigments that give a leaf its color can be separated and observed to determine the Rf value of each pigment and their function during photosynthesis.

 

Materials
For this experiment the following items are used — one chromatography reaction chamber, one paper chromatography strip, one capillary pipette, a pencil and paper, calculator, ruler, 50 ml beaker, colored pencils, approximately 10 ml of solvent depending on the size of the reaction chamber, scissors, and simulated plant pigment.

 

Procedure
Use scissors to cut the bottom of the chromatography paper to a tapered end. Measure the strip and cut the length to equal slightly longer than the reaction chamber. Draw a faint pencil line at the bottom of the tapered end and use a capillary pipette to add some simulated plant pigment to this line. Add 5-10 ml of solvent to the reaction chamber. Extend the chromatography strip through the slit in the lids of the reaction chamber and carefully lower the strip into the chamber so the tapered end is in the solvent and the pencil line is above the solvent level. Make sure the strip does not touch the walls of the chamber and do not bump the chamber as the pigments begin to separate. After the pigments have completely separated and the solvent front has reached the top of the chamber, remove the strip and mark the solvent front with a pencil line before it evaporates. Measure and record the distance the solvent and each pigment traveled. Use a calculator to determine the Rf values for each pigment.

 

Data

 

Table 1

Band # Pigment Color Migration distance (mm) Rf value
1 Carotene Orange 59mm .94
2 Xanthophyll Yellow 56mm .89
3 Chlorophyll a Light green 29mm .46
4 Chlorophyll b Dark green 14mm .22
Solvent 63mm

Questions
1. Describe what happened to the original spot of simulated plant pigments?
  The solvent separated  the original spot by wicking up the solvent while dissolving the various pigments in the spot.
2. List some other uses of chromatography?  Chromatography can be used to separate various mixtures of subtances, liquids and gases.
3. Which of the 4 pigments migrated the furthest and why?  carotene ( orange) because it was the most soluble in the solvent
4. Which type of chlorophyll was the most soluble?  chlorophyll a
5. Explain why leaves change color in the fall?  In Autumn, chlorophyll starts to break down which allows the other brilliant plant pigment colors to show. These pigments include the red, orange, and yellow colors.
6. What is the function of plant pigments in photosynthesis?  Plant pigments trap light energy and convert it into chemical energy that can be used by the plant to make glucose or sugar.

Error Analysis
The chromatography paper touched the sides of the chamber during the waiting time which caused the migration to go slightly to the side instead of straight to the top. Also the strip was bent at the top so there could have been a slight error in measuring the migration of the solvent  front.

Conclusion
Paper chromatography proved to be an accurate method of separating and observing the various colors of plant pigments. The pigments dissolved in the solvent and migrated upward. The colors were observed and their migration distances measured & recorded. The
Rf value of each pigment was determined by dividing its migration by the migration of the solvent.  It was determined that 4 pigments were present in the original spot — carotene, xanthophyll, chlorophyll a, and chlorophyll b. Carotene was the most soluble, while chlorophyll b was the least soluble.

Chlorophyll Fluorescence

 

Chlorophyll Fluorescence

INTRODUCTION

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.

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

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 using proper filtering technique, filter the extract to a test tube. NOTE: Use a small amount of acetone to wet the filter paper, to hold it into place, instead of water.

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.

 

Chromatography Lab

Chromatography Lab

Problem:  How do you separate the different pigments in a plant?

Materials:

Cone-type (size 4) coffee filter paper (or Whatman #1 chromatography paper)
large glass jars
acetone
distilled water
capillary tubes
fresh spinach
mortar and pestle
clean sand

Introduction:

In this activity you will be experimenting with a technique called chromatography which will allow you to visually demonstrate that the pigment in leaves is a combination of several different colored pigments.

This technique is useful in that it can separate and identify the various components of mixtures, such as those contained in plant pigments. A pigment is a substance that absorbs light at specific wavelengths, chlorophyll is one of these pigments. Its green-yellow in color is due to the absorption of red, orange, blue, and violet wavelengths and the reflection of the green and yellow wavelengths.   This occurs when white light (containing all of the light wavelengths, or the entire spectrum of colors) shines on the leaf surface, all of the wavelengths are absorbed except for the ones you see, which are green-yellow, those are the portions of the spectrum being reflected.

If the conditions are identical, the relative distance moved by a particular compound is the same from one mixture to another. This is why chromatography can be used to identify a compound. The actual identification requires a simple calculation as shown below:

Rf = distance moved by compound from original spot divided by the distance moved by solvent from original spot

It is important to remember that several factors can influence the reliability of the Rf value, these include humidity, temperature, solvent, pigment extract preparation, and the amounts of the material present.  Values are comparable only when the extracts are prepared in the same way and the chromatograms are prepared identically and developed together in the same container.

Acetone is flammable (even the amount found in nail polish remover), keep it away from sparks or open flames. Wear eye protection, especially if using pure acetone.

Procedure

1.   Each lab group (or individual if not working in groups) will need 4 strips of filter paper, approximately 6 inches long and 1 inch wide, 2 chromatography development containers (500 ml beakers or large fruit jars work well), 2 large rubber bands (able to stretch around the vessels from the mouth to the bottom of the vessel), 2 solvents, water and either pure acetone, or nail polish remover.

2.   Do the following with both fresh spinach leaves; tear leaf material and place in a glass container, cover with acetone (this should be done the day before the actual lab activity). An alternative pigment extraction technique is to use a
mortar and pestle. Place plant material the vessel, add a little clean sand, some acetone and then grind until a dark green liquid appears.    Both techniques yield very dark pigments with which to work. Be certain to keep the pigments apart throughout the entire activity.

3.   Place one of each solvents (water and acetone, or nail polish remover) in the chromatography vessels and stretch a rubber band length-wise around each vessel. The rubber band will be the mechanism for hanging the chromatography strips.

4.   Make a pencil mark on each of the 2 chromatography strips, in the center, directly above the point of the strip, about 1 inch from the tip of the paper. Using a capillary tube, or tooth pick, apply the plant pigment to each filter paper strip. This is done by touching the tooth pick or capillary tube which has been dipped in the pigment, to the pencil mark. Make an application, then wave the paper gently to dry it a little before the next application. Be patient, you will need 12 to 15 applications.

5.   By now you should have 2 strips with spinach pigment.  Suspend one of each in each of the chromatography development vessels. You can attach them with paper clips, or simply fold over a portion of the end and it should hang in place. The tip of each strip should just touch the solvent.

6.   Wait 20 to 30 minutes for the chromatograms to develop. Remove the chromatograms. Mark with a pencil (NOT a pen) where the solvent stopped as it moved up the chromatogram. This is called the solvent front. Mark also where each pigment stopped moving up the chromatogram. Using the equation below, determine a reference number for each pigment on the chromatograms. Depending on which chromatogram you are viewing, you should see greens, yellow/yellow orange, and red. All measurements should be in mm. (Any material which did not move from the
pencil dot is insoluble).

Rf = distance moved by compound from original spot divided by the
distance moved by solvent from original spot

Note: each pigment has a special name,
green = chlorophyll a or b
yellow/yellow orange = carotene
red = anthocyanin
brown = xanthophyll

The reference numbers for the chlorophylls in this activity are:
0.28 = chlorophyll a, 0.18 = chlorophyll b (spinach). You need these
numbers so that you can determine one chlorophyll from the other.
Calculate reference fronts for all of your pigments.

See if your calculations come close to those above for chlorophyll a and b.

Note:  You can use different solvents such as mixtures involving petroleum ether
to do this sort of paper chromatography.

To view notes and a graphic showing a separation of plant pigments involving
paper chromatography, click here.  Can you calculate the Rf values for the
pigments separated in this graphic?

Conclusion Questions

1.  What reference numbers (Rf) did you calculate for chlorophyll a and chlorophyll b?
2.  With what you have discovered about pigments, what conclusions can you
make regarding the changing color of leaves in autumn?
3.  What adaptive purpose do different colored pigments serve for a plant?
4.  Why do some pigments move farther up the chromatogram than others?
5.  What are some possible sources of error in this lab?

Paper chromatography is a technique used to separate a mixture into its component molecules. The molecules migrate, or move up the paper, at different rates because of differences in solubility, molecular mass, and hydrogen bonding with the paper.

For a simple, beautiful example of this technique, draw a large circle in the center of a piece of filter paper with a black water-soluble, felt-tip pen. Fold the paper into a cone and place the tip in a container of water. In just a few minutes you will have tie-dyed filter paper!

Separation of black ink pigments

The green, blue, red, and lavender colors that came from the black ink should help you to understand that what appears to be a single color may in fact be a material composed of many different pigments —and such is the case with chloroplasts.

chromatography setup

 

In paper chromatography the pigments are dissolved in a solvent that carries them up the paper. In the ink example, the solvent is water. To separate the pigments of the chloroplasts, you must use an organic solvent

 

 

pigment separation

 

pigment separation

 

Analysis of Results I

If you did a number of chromatographic separations, each for a different length of time, the pigments would migrate a different distance on each run. However, the migration of each pigment relative to the migration of the solvent would not change. This migration of pigment relative to migration of solvent is expressed as a constant, Rf (Reference front). It can be calculated by using the formula:

 

Chromatography of Plant Pigments 3

 

 

Chromatography of Plant Pigments

 

 

Introduction:

 

Can chromatography be used to separate mixtures of chemical substances? The purpose of this experiment is to answer this question. In paper chromatography, a liquid sample flows down a vertical strip of absorbent paper, on which the components of a mixture are deposited in specific directions and locations. Chromatography is a tool used to examine and separate mixtures of chemical substances. Chromatography is essential to the separation of pure substances from complex mixtures. Separation results in a chromatographically pure substance. Chromatography allows you to determine the properties of chemical substances.

The relationship between the chromatography paper, mixture, and the solvent is very important in all chromatographic separations. The solvent has to dissolve the mixture that should be separated. The paper must also absorb the components of the mixtures selectively and reversibly. The substances making up the mixture must be evenly dispersed in the water. Chromatography is a simple and inexpensive tool for separating and identifying chemical mixtures if all these things are done.

 

Hypothesis:

 

Paper can be used to separate mixed chemicals.

 

Materials:

 

The materials used in this lab are filter paper, test tube, rubber stopper, paper clip, metric ruler, black felt-tip pen, pencil, calculator, and water.

 

Methods:

 

First, bend a paper clip so that it’s straight with a hook at one end. Push the straight end of the paper clip into the bottom of a cork stopper. Then, hang a thin strip of filter paper on the hooked end of the paper clip and insert the paper strip into the test tube. The paper should not touch the sides and should almost touch the bottom of the test tube. Next, remove the paper strip from the test tube. Now draw a solid 5-mm-wide band about 25 mm from the bottom of the paper, using a black felt tip pen. After this, use a pencil to draw a line across the paper strip 10 cm above the black band. Then, put the filter paper back into the test tube with the bottom of the paper in the water and the black band above the water. Observe what happens as the liquid travels up the paper and record the changes you see. When the solvent has reached the pencil line, remove the paper from the test tube. Let the paper dry on the desk. Finally, with a metric ruler, measure the distances from the starting point to the top edge of each color. Record the data in a data table and calculate a ratio for each color by dividing the distance, the color traveled by the distance the solvent traveled.

 

Results:

 

The results of the chromatography experiment are shown in a chart and a graph.

 

Color of ink (list in order) Distance traveled by each color (mm) Distance solvent traveled (mm) Ratio traveled = distance color moved divided by distance solvent moved
Yellow 70 108 0.65
Orange  

85

 

108

 

0.79

Pink 95  

108

 

0.88

Violet 102  

108

 

0.94

Blue 108  

108

 

1.00

 

 

 

Questions:

1. How many colors separated from the black ink? Five colors separated from the ink: yellow, orange, pink, violet, and blue.

 

2. What served as the solvent for the ink? Water served as the solvent for the ink.

 

3. As the solvent traveled up the paper, which color of ink appeared first? Dark blue appeared first.

 

4. List the colors in order from top to bottom that separated from the black ink? The colors separated in the order of: blue, violet, pink, orange, and yellow.

 

5. In millimeters, how far did the solvent travel? The solvent traveled 108 mm.

 

6. From your results, what can you conclude is true about black ink? Black ink is a mixture of several different colors.

 

7. Why did the inks separate? The inks separated because black ink is a mixture of different pigments that are soluble in water, have different molecular characteristics, and travel different distances.

 

8. Why did some inks move a greater distance? Some inks move a greater distance because molecules in ink have different characteristics, like how readily they are absorbed by paper. This means that the ink least readily absorbed by paper will travel farthest from the starting mark and the ink most readily absorbed by paper will be the closest to the starting mark. All of the different color inks that were separated were different in how readily they are absorbed by paper.

Error Analysis:

 

There are a few errors that could have changed the results. First, there could be inaccurate measurements of how far every color traveled or how far the water traveled up the filter paper. Another error could occur when calculating the ratio traveled, Rf value. Also, a longer test tube could have been used by different groups which would make the filter strip longer. This means that a group could have detected another color because they had more room on their filter paper. This also could have affected the ratios. Finally, the groups could have put different amounts of black ink on the filter paper.

 

Conclusion:

 

The hypothesis that paper can be used to separate mixed chemicals was correct. The different colored inks mixed together give the black its color. The five colors that separated from the black ink were blue, violet, pink, orange, and yellow. Blue appeared first and then was followed by violet, pink, orange, and yellow. The colors separated the way they did because they have different molecular characteristics, like how readily they were absorbed by the paper and their solubility in water. Blue was most readily absorbed by the paper and soluble by water, while yellow was the least.

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Chapter 29 AP Objectives

 

Chapter 29     Plant Diversity I: Colonization of Land
Objectives
An Overview of Land Plant Evolution
1. Describe four shared derived homologies that link charophyceans and land plants.
2. Distinguish among the kingdoms Plantae, Streptophyta, and Viridiplantae. Note which of these is used in the textbook.
3. Describe five characteristics that distinguish land plants from charophycean algae. Explain how these features are adaptive for life on land.
4. Define and distinguish among the stages of the alternation of generations life cycle
5. Describe evidence that suggests that plants arose roughly 475 million years ago.
Bryophytes
6. List and distinguish among the three phyla of bryophytes. Briefly describe the characteristics of each group.
7. Distinguish between the phylum Bryophyta and the bryophytes.
8. Explain why bryophyte rhizoids are not considered roots.
9. Explain why most bryophytes grow close to the ground.
10. Diagram the life cycle of a bryophyte. Label the gametophyte and sporophyte stages and the locations of gamete production, fertilization, and spore production.
11. Describe the ecological and economic significance of bryophytes.
The Origin and Diversity of Vascular Plants
12. Describe the five traits that characterize modern vascular plants. Explain how these characteristics have contributed to their success on land.
13. Distinguish between microphylls and megaphylls.
14. Distinguish between the homosporous and heterosporous condition.
15. Explain why seedless vascular plants are most commonly found in damp habitats.
16. Name the two clades of living seedless vascular plants.
17. Explain how vascular plants differ from bryophytes.
18. Distinguish between giant and small lycophytes.
19. Explain why whisk ferns are no longer considered to be “living fossils.”
20. Describe the production and dispersal of fern spores.
Student Misconceptions
21. Many students have difficulty in understanding the significance of derived characters that are shared between two extant groups. Just as many members of the general public have the mistaken notion that humans evolved from chimpanzees, some students will think that charophyceans are in some sense ancestral to plants or that charophyceans are identical to the last common ancestor that plants and charophyceans shared.
22. It is important to make sure that your students understand alternation of generations in bryophytes and seedless vascular plants. Plant life cycles are challenging for all students. Without a good understanding of the life cycles of plants with recognizable gametophytes and sporophytes, students will have great difficulty with gymnosperm and angiosperm life cycles.
23. Students tend to think of derived traits as “advanced.” Be careful to avoid this term. Point out that organisms have a combination of primitive and derived traits, and that all living organisms have an equally long evolutionary history, dating back to the origin of life on Earth.
24. Many students are not very familiar with or knowledgeable about plants. Some of the terminology of plant life cycles can be confusing to such students. Clarify for students the meaning of these pairs of terms:
a. homosporous and heterosporous
b. bryophyte and phylum Bryophyta
c. rhizoid and root
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Chapter 30 AP Objectives

 

Chapter 30     Plant Diversity II: The Evolution of Seed Pants
Objectives
Key Terrestrial Adaptations Were Crucial to the
Success of Seed Plants
1. Name five terrestrial adaptations that contributed to the success of seed plants.
2. Compare the size and independence of the gametophytes of bryophytes with those of seed plants.
3. Describe the ovule of a seed plant.
4. Contrast the male gametophytes of bryophytes with those of seed plants.
5. Explain why pollen grains were an important adaptation for successful reproduction on land.
6. Explain how a seed can be said to include contributions from three distinct generations.
7. Compare spores with seeds as dispersal stages in plant life cycles.
Gymnosperms
8. Explain how climatic changes with the formation of the supercontinent Pangaea favored the spread of gymnosperms.
9. List and distinguish among the four phyla of gymnosperms.
10. Describe the life history of a pine. Indicate which structures are part of the gametophyte generation and which are part of the sporophyte generation.
Angiosperms (Flowering Plants)
11. Identify the following floral structures and describe a function for each:

a. sepal f. anther
b. petal g. stigma
c. stamen h. style
d. carpel i. ovary
e. filament j. ovule
12. Define fruit. Explain how fruits may be adapted to disperse seeds.
13. Explain why a cereal grain is a fruit rather than a seed.
14. Diagram the generalized life cycle of an angiosperm. Indicate which structures are part of the gametophyte generation and which are part of the sporophyte generation.
15. Describe the role of the generative cell and the tube cell within the angiosperm pollen grain.
16. Explain the process and function of double fertilization.
17. Explain the significance of Archaefructus.
18. Explain the significance of Amborella.
19. Distinguish between monocots and eudicots.
20. Explain how animals may have influenced the evolution of terrestrial plants and vice versa.
Plants and Human Welfare
21. Name the six angiosperms that are most important in the diet of the human species.
22. Describe the current threat to plant diversity caused by human population growth.

.

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Chapter 35 AP Objectives

 

Chapter 35     Plant Structure and Growth
Objectives
The Plant Body
1. Describe and compare the three basic organs of vascular plants. Explain how these basic organs are interdependent.
2. List the basic functions of roots. Describe and compare the structures and functions of fibrous roots, taproots, root hairs, and adventitious roots.
3. Describe the basic structure of plant stems.
4. Explain the phenomenon of apical dominance.
5. Describe the structures and functions of four types of modified shoots.
6. Describe and distinguish between the leaves of monocots and those of eudicots.
7. Describe the three tissue systems that make up plant organs.
8. Describe and distinguish between the three basic cell types of plant tissues. For each tissue, describe one characteristic structural feature and explain its functional significance.
9. Explain the functional relationship between a sieve-tube member and its companion cell.
The Process of Plant Growth and Development
10. Distinguish between determinate and indeterminate growth. Give an example of each type of growth.
11. Distinguish among annual, biennial, and perennial plants.
12. Explain this statement: “In contrast to most animals, which have a stage of embryonic growth, plants have regions of embryonic growth.”
13. Distinguish between the primary and secondary plant body.
14. Describe in detail the primary growth of the tissues of roots and shoots.
15. Describe in detail the secondary growth of the tissues of roots and shoots.
16. Name the cells that make up the tissue known as wood. Name the tissues that comprise the bark.
Mechanisms of Plant Growth and Development
17. Explain why Arabidopsis is an excellent model for the study of plant development.
18. Explain what each of these Arabidopsis mutants has taught us about plant development:
a. fass mutant
b. gnom mutant
c. KNOTTED-1 mutant
d. GLABRA-2 mutant
19. Define and distinguish between morphogenesis, differentiation, and growth.
20. Explain why (a) the plane and symmetry of cell division, (b) the orientation of cell expansion, and (c) cortical microtubules are important determinants of plant growth and development.
21. Explain how pattern formation may be determined in plants.
22. Give an example to demonstrate how a cell’s location influences its developmental fate.
23. Explain how a vegetative shoot tip changes into a floral meristem.
24. Describe how three classes of organ identity genes interact to produce the spatial pattern of floral organs in Arabidopsis.
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Chapter 36 AP Objectives

Chapter 36     Transport in Plants
Objectives
An Overview of Transport Mechanisms in Plants
1. Describe how proton pumps function in transport of materials across plant membranes, using the terms proton gradient, membrane potential, cotransport, and chemiosmosis.
2. Define osmosis and water potential. Explain how water potential is measured.
3. Explain how solutes and pressure affect water potential.
4. Explain how the physical properties of plant cells are changed when the plant is placed into solutions that have higher, lower, or the same solute concentration.
5. Define the terms flaccid, plasmolyze, turgor pressure, and turgid.
6. Explain how aquaporins affect the rate of water transport across membranes.
7. Name the three major compartments in vacuolated plant cells.
8. Distinguish between the symplast and the apoplast.
9. Describe three routes available for lateral transport in plants.
10. Define bulk flow and describe the forces that generate pressure in the vascular tissue of plants.
11. Relate the structure of sieve-tube cells, vessel cells, and tracheids to their functions in bulk flow.
Absorption of Water and Minerals by Roots
12. Explain what routes are available to water and minerals moving into the vascular cylinder of the root.
13. Explain how mycorrhizae enhance uptake of materials by roots.
14. Explain how the endodermis functions as a selective barrier between the root cortex and vascular cylinder.
Transport of Xylem Sap
15. Describe the potential and limits of root pressure to move xylem sap.
16. Define the terms transpiration and guttation.
17. Explain how transpirational pull moves xylem sap up from the root tips to the leaves.
18. Explain how cavitation prevents the transport of water through xylem vessels.
19. Explain this statement: “The ascent of xylem sap is ultimately solar powered.”
The Control of Transpiration
20. Explain the importance and costs of the extensive inner surface area of a leaf.
21. Discuss the factors that may alter the stomatal density of a leaf.
22. Describe the role of guard cells in photosynthesis-transpiration.
23. Explain how and when stomata open and close. Describe the cues that trigger stomatal opening at dawn.
24. Explain how xerophytes reduce transpiration.
25. Describe crassulacean acid metabolism and explain why it is an important adaptation to reduce transpiration in arid environments.
Translocation of Phloem Sap
26. Define and describe the process of translocation. Trace the path of phloem sap from a primary sugar source to a sugar sink.
27. Describe the process of sugar loading and unloading.
28. Define pressure flow. Explain the significance of this process in angiosperms.
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Chapter 37 AP Objectives

 

Chapter 37     Nutrition in Plants
Objectives
Nutritional Requirements of Plants
1. Describe the ecological role of plants in transforming inorganic molecules into organic compounds.
2. Define the term essential nutrient.
3. Explain how hydroponic culture is used to determine which minerals are essential nutrients.
4. Distinguish between macronutrient and micronutrient.
5. Name the nine macronutrients required by plants.
6. List the eight micronutrients required by plants and explain why plants need only minute quantities of these elements.
7. Explain how a nutrient’s role and mobility determine the symptoms of a mineral deficiency.
The Role of Soil in Plant Nutrition
8. Define soil texture and soil composition.
9. Explain how soil is formed.
10. Name the components of topsoil.
11. Describe the composition of loams and explain why they are the most fertile soils.
12. Explain how humus contributes to the texture and composition of soils.
13. Explain why plants cannot extract all of the water in soil.
14. Explain how the presence of clay in soil helps prevent the leaching of mineral cations.
15. Define cation exchange, explain why it is necessary for plant nutrition, and describe how plants can stimulate the process.
16. Explain why soil management is necessary in agricultural systems but not in natural ecosystems such as forests and grasslands. Describe an example of human mismanagement of soil.
17. List the three mineral elements that are most commonly deficient in agricultural soils.
18. Explain how soil pH determines the effectiveness of fertilizers and a plant’s ability to absorb specific mineral nutrients.
19. Describe problems resulting from farm irrigation in arid regions.
20. Describe actions that can reduce loss of topsoil due to erosion.
21. Explain how phytoremediation can help detoxify polluted soil.
The Special Case of Nitrogen as a Plant Nutrient
22. Define nitrogen fixation and write an overall equation representing the conversion of gaseous nitrogen to ammonia.
23. Explain the importance of nitrogen-fixing bacteria to life on Earth.
24. Summarize the ecological role of each of the following groups of bacteria.
a. ammonifying bacteria
b. denitrifying bacteria
c. nitrogen-fixing bacteria
d. nitrifying bacteria
25. Explain why improving the protein yield of crops is a major goal of agricultural research.
Nutritional Adaptations: Symbiosis of Plants and Soil Microbes
26. Describe the development of a root nodule in a legume.
27. Explain how a legume protects its nitrogen-fixing bacteria from free oxygen, and explain why this protection is necessary.
28. Describe the basis for crop rotation.
29. Explain why a symbiosis between a legume and its nitrogen-fixing bacteria is considered to be mutualistic.
30. Explain why a symbiosis between a plant and a mycorrhizal fungus is considered to be mutualistic.
31. Distinguish between ectomycorrhizae and endomycorrhizae.
Nutritional Adaptations: Parasitism and Predation by Plants
32. Name one modification for nutrition in each of the following groups of plants:
a. epiphytes
b. parasitic plants
c. carnivorous plants
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