Category: Plants

 

 

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.

 

 

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

 

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.

 

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     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     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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