A Big Idea: Fast Plants, Environment, Heredity and You

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1 WFP A Big Idea: Fast Plants, Environment, Heredity and You One of the big ideas in biology is addressed in the following activity and is captured in the question, Who are you? Huh? Answer: you are you because of your heredity, the genes you inherited from your parents and you are also you because of how you live (your environment), and because of your age (your stage of development) Figure 1. Your Physical Age (Development) This rather abstract notion embraces a number of the fundamental ideas that will help you better understand life on earth. Think about it. Like you, every living organism, at any moment in its life, is what it is because its genes, inherited from its parents, have guided it s development through all the environmental conditions under which it has lived and grown. Understanding more about how your environment influences who you are is important. You can use the experimental organism called Fast Plants to investigate various aspects of this big idea. In Activity I, you will learn how the environment and heredity influences plant growth and development. In further activities, you will come to understand how heredity (genetics) influences plant appearance (phenotype). Activity I: "Is More Food Better?" Environment Chemical (What you eat and do) Life Processes YOU and Systems Heredity Biological (Genes from your parents) Figure 1: Venn diagram illustrating the relationship between the environment, heredity, age, and you. Introduction Because of their ease of growth and short life cycle (seed to seed in 35 days) Fast Plants are an organism suitable for many kinds of home and classroom scientific investigations. They are particularly interesting because, like humans, they exhibit considerable variation in many observable characteristics. Fast Plants are useful for experiments investigating the effects of environment (light, nutrition, etc.) on variation in growth, development and reproduction. This activity addresses the effect of nutrient on growth and reproduction. Specifically you will investigate how much fertilizer (nutrient or plant food) is best for the production of a crop of Fast Plants seed. This is the same question that farmers ask every time they plant a crop. An Observation Farmers and gardeners generally believe that more fertilizer (plant food) is better for plant growth and crop production. But do they really know how much food is better? The Question This investigation is designed to examine the question Is more food better for Fast Plants? Better, of course, depends on the perspective or point of view you choose to take and can differ widely. For example, if you were a farmer growing Fast Plants, would you be growing the plants for feeding to cattle and sheep, for salad greens, or for a crop of seed to sell? For the purposes of this investigation you should consider the production of seed to be used by you and your friends for future experiments as the goal for determining better. Therefore, more seed is better.

2 The Hypothesis In a scientific investigation the conversion of a question, such as Is more food better?, into a hypothesis (statement) that claims more food is better for Fast Plants seed production is a way of examining the question. Making a hypothesis is a useful approach to an investigation because you can experimentally generate evidence that tests (supports or disagrees with) the hypothesis. Experimental Design (Testing the Hypothesis) You will grow a crop of Fast Plants for seed using a simple planting design in soda bottles (Bottle Growing System or BGS) and a Plant Light House made from a paper box and a low-cost energy saver fluorescent circular bulb. This equipment provides optimal environmental conditions for growth. Under these standard conditions, the investigation introduces a single environmental variable, nutrients (fertilizer). You will first create three dilutions of chemical fertilizer to be used in growing your plants. Six BGSs with six Fast Plants in each will be grown under three different treatment levels of nutrients; two BGSs (n= 12 plants) for each nutrient level. Individual plants in each set of 12 plants will be numbered and observed, and selected traits representing growth (height), development (# of leaves, # of hairs) and reproduction (# of flowers pollinated and # of seeds produced) will be measured and recorded in the growth, development and reproduction (GDR) Tables. You will thus have collected important sets of data representing the growth, development and reproduction of the three sets of 12 plants which you have grown under the three nutrient levels. After summarizing and graphing these data, you will be able to determine which plant traits are influenced by the nutrient environment and by how much they are affected. From the knowledge of plants which you gain in this investigation and from the data that you generate, you ll be able to evaluate the hypothesis, More food (nutrient) is better for seed production. In addition to seed production you will observe that nutrition influences some traits a lot and some very little, if at all. You will also find out that within a population of Fast Plants, as with humans and many other organisms, some traits vary a lot and are influenced by nutrition whereas other traits vary a lot and are little influenced by nutrition. Yet other traits vary only a little and are not influenced by the growing environment. This insight will lead you to a second activity concerning the inheritance of a particular plant trait hairs. Knowledge of how the relative roles of the environment and heredity influence the appearance of organisms will lead you to a better understanding of the organisms and of yourself. Prepare the Equipment and Materials Construct a Plant Light House Make six Bottle Growing Systems (BGS) Make a water bottle Prepare the Nutrient Solutions 2 Figure 2: Excerpt from the new Fast Plants manual.

3 Construction of the Plant Light House Materials one empty "copy paper" box, e.g., Xerox aluminum foil, 12 inch wide electrical cord with socket plastic plate or lid glue stick clear tape (3/4") scissors, cutting blade for card board 30 watt fluorescent circle light (Lights of America) or a 39 watt (GE) energy savers Construction 1. Cut a 1 inch hole in the center of a plastic plate or lid and trim off edges to make approximately a 4-5 inch disk with a center hole. 2. Cut three 4 X 14 cm ventilation slots in top, upper sides and back of box as shown. 3. Cut a 1 inch diameter hole in the center of box. 4. Apply glue stick to the inner surfaces and paste in aluminium foil to cover entire surface. Use clear tape to reinforce corners and edges. 5. Insert light fixture base through hole in top and through plastic plate. Secure fixture by attaching socket and cord. 6. Tape an aluminum foil or reflective full length plastic curtain over front from the top front edge of box. Figure 3. Plant Light House 7. Strengthen curtain edges and middle with tape. Tape or clip light weight (paint stirrer or small stick on bottom of curtain. If desired, attach environmental monitering devices (e.g. indoor / outdoor digital thermometer) using Velco tape. Making Six Bottle Growing Systems (BGS) Materials six 16, 20, or 24 oz. soda bottles small knife, or blade scissors Watermat for capillary wicks (from kit) optional, matte black spray paing Construction 1. With a knife or blade, make a 2-3 cm puncture in the upper body of each bottle 2-3 cm below the rim of the shoulder. Insert scissors in the puncture and cut around each soda bottle to create the growing funnel with a 0.5 cm rim beyond the shoulder (Figure 4). This will hold the planting medium. 2

4 2. With scissors, cut the bottom portion of each bottle to create a reservoir 10 cm tall. (Fig. 2). (A single Plant Light House can accommodate 8 BGSs.) Bottle Growing System (BGS) (From here on, the instructions refer to a single BGS.) 3. Drill or melt a 5 mm hole in the bottle cap. Screw bottle cap onto bottle top. From the square of Watermat material cut six 0.7 to 10 cm capillary wicks. Taper the ends to a point. Insert one capillary wick through the hole in each bottle cap. Wet the wick before planting to be sure that it draws water well. 4. Invert the growing funnel (bottle top) and place in the bottle reservoir (bottle base.) The wick should extend from the funnel to the floor of the reservoir. cut 0.5 cm below rim of shoulder 8 cm from bottom drill 5-mm hole in Figure 4. Bottle Growing System, BGS vermiculite planting medium nutrient reservoir 5. Optional. To prevent algal growth in the nutrient solution, spray paint with matte black the outer surface of the bottle reservoir. Before painting, tape a strip of 1/2 inch tape vertically from the top to the bottom of the reservoir. After painting, remove the tape to create a window to view the nutrient level in the reservoir. Making a Water Bottle Materials one 16, 20 or 24 oz. soda bottle with cap small pliers small nail or paper clip candle Construction 1. Make a water bottle from a small soda bottle. Holding it with pliers, first heat a small nail or paper clip wire in a candle flame. Then melt a hole (about 1 mm diameter) in the center of the soda bottle cap with the heated nail. 2. Fill the bottle with water, screw on the cap and you have a water bottle. Turn bottle upside down and squeeze. You should get a small stream of water. Preparing the Nutrient Solutions Materials 4, 2-liter soda bottles with caps (remove bottle labels by adding hot tap water to bottle or blowing hot air from hair dryer and peeling label off) permanent marking pen metric kitchen measuring cup kitchen funnel packet of Peters Professional, fertilizer with minor elements (from kit) 4

5 Preparation 1. With a permanent marking pen, mark the 1-liter and 2-liter levels on the side of 4 empty 2-liter soda bottles. Use a funnel to add a first and then a second liter of water and marking their levels. 2. To make the stock solution (1X concentration) add 2 level soda bottle capfuls of Peters fertilizer powder. Then add water to the 2 liter level. Note: scientists call this the stock solution because it is the solution from which other dilutions are made. Label this bottle 1X stock solution, Peters Date it. 2 Liters 2 Liters 2 Liters 1/32X 1/16X 1/8X N-P-K N-P-K N-P-K 3. To make the 1/8X solution, add 250 ml of stock solution into a bottle labeled 1/8X, Peters and add water until it reaches the 2 liter mark. Do you understand why this solution is now 1/8X? 4. To make the 1/16X solution add 1 liter of 1/8X solution (half your 1/8X supply) to another bottle Figure 2: Three two liter bottles each filled with different concentrations of nutrient solution, 1/32 strength, 1/16 strength, and 1/8 strength labeled 1/16X, Peters ) and add water until it reaches the 2 liter mark. Do you understand why this solution is now 1/16X? 5. Repeat the process from #5, using the 1/16X solution, into the last bottle labeled 1/32X, Peters Can you explain why this solution is now 1/32X? You have now made a series of dilutions from 1/8X to 1/16X to 1/32 X. This is called a dilution series. 6. Store the bottles of nutrient solution in a dark closet or box to prevent the growth of algae in the solutions. Food for thought Think about the dilutions (mixtures) of nutrient solution that you have just made. 1. How much more dilute is the 1/8X than the 1X nutrient solution? 2. How much more dilute is the 1/16X than the 1/8X nutrient solution? 3. Which dilution contains the most water compared to the amount of nutrient? 4. How much more dilute is the 1/32X than the 1/16X nutrient solution? 5. Do you think you could construct another dilution series using different amounts? How would you do it? 6. Could you make a graph of your dilution series showing the amount of water on the x axis and the amount of fertilizer on the y axis at each dilution you make? When you are graphing the data for your first set of experiments you will be recording the nutrient concentration as the independent variable on the horizontal or x axis of the graph. Think about how you will do this. 5

6 Begin the Investigation Materials quick drying glue, e.g., Duco Cement 10 X 10 cm square of Watermat or heavy, unpolished cotton string for capillary wicks bag of planting medium pack of dried honey bees and round toothpicks formaking beesticks pack of 100 Fast Plants seeds 10X hand lens Figure 6: Three Bottle Growing Systems, BGS. Each designed to hold a different concentrations of nutrient solution, 1/32 strength, 1/16 strength, and 1/8 strength Planting 1. In a bucket or tub gently moisten the planting medium with a very little water so that it just feels moist (not wet) to touch. Mix it well so that it is loose and fluffy. Then transfer approximately 150 cc of planting medium into the funnel of each BGS so that it loosely fills the funnel to heaping. Tap the funnel to help the planting medium settle, then level off the excess so the planting medium is level with the top of the funnel. Do not press or compact the planting medium. Place the funnel with soil in a bottle reservoir Location of seeds in BGS Gently soak the planting medium with tap water from your water bottle, letting the water percolate through until it drips into the reservoir of the BGS from the wick at the bottom of the growing funnel. This is called the runoff. The layer of planting medium should shrink down in the funnel about cm from the rim For each BGS, uniformly distribute Fast Plants seeds on the surface of the moist planting medium around the perimeter of the funnel about 5 mm from the clear wall. (See illustration) 4. Cover the seeds with a thin (approximately 0.5 cm) layer of the planting medium so that it is level with the rim of the growing funnel. 5. With your water bottle, gently re-moisten the planting medium in your BGS with tap water again until water drips from the wick at the base of the funnel. 6. Pour off the runoff water remaining in the reservoirs. Then fill two of the reservoirs with about 250 ml of the 1/8 strength nutrient solution. This creates a hydroponic growing system for the plants. Label these reservoirs as 1/8X nutrient. Follow the same procedure by filling and labeling two of the other reservoirs with 1/16X nutrient solution and the remaining two with the 1/32X nutrient solution. Label them appropriately. Figure 7. GDR Table. Raw data from Paul Williams' research notebook. (Fast Plants growth and development data) 6

7 7. Put all six BGSs in the Plant Light House. Keep light on 24 hours a day. 8. Prepare three Fast Plants Growth, Development and Reproduction (GDR) Data Charts, one for each nutrient level. Fill in the information at the top of each chart. Record the date and time of planting on your growth charts. 9. At Day 5-7 after sowing (das), thin the plants in each BGS to 6 plants. Number the plants in each nutrient treatment from 1 to If you can, monitor and record the temperature inside the Plant Light House each day. If average temperatures within the Plant Light House exceed 30 C/ 85 F, additional ventilation slots can be cut in the top and upper portions of the Light House. Excessive temperatures, either high or low, will affect the plants. 11. Check the level of the nutrient solution in the BGSs each day and replenish as needed. Algal growth in the nutrient solution can be inhibited by wrapping the reservoir in aluminum foil or dark paper to exclude light. Optionally, you may wish to keep a record of the amount of nutrient solution used in each BGS. 12. Each day or two carefully inspect your plants, observing any differences and similarities in the plants within and among the three nutrient treatments. Can you see any differences among individual plant within a nutrient treatment level or between nutrient treatments? If you can, describe them. Observing, Measuring and Recording Data* (for each plant at each nutrient treatment level) # of leaves on the main stem, including cotyledons count number of hairs on margin of 1 st true leaf, das (Use a 10X hand lens) total # of flowers pollinated, 18 das after termination of flowering record height in mm at 18 das after termination of flowering total # of seeds per plant flowers hairs on margin of first true leaf 1. At about das just as the first flowers are beginning to open, you should make two kinds of observations and counts on each plant of each nutritional treatment level and record your counts in the appropriate GDR table (Figure 7). The first count is the number of leaves, including the seed leaves (cotyledons) and small leaf-like structures near the 1 st flower buds that attach to the main stem (not branches) of the Fast Plants. Refer to Figure 8, an illustration of the Fast Plant, to determine the leaves to be counted. 2. The second count may be challenging for you and will require the aid of a 10X hand lens or a dissecting microscope. This count will be the number of tiny hairs that can be seen growing from the edge all around the margin of the first true leaf above the cotyledons on the stem of the Fast Plant. (See Figure 8 for identification of the 1 st true leaf and of the hairs to be counted.) Hairs are found on many parts of Fast Plant leaves and stems. Only count those on the leaf edge, not on the top or bottom or leaf stem. 7 second true leaf seed leaf (cotyledon) first true leaf Figure 8: Caricature of a Fast Plants illustrating different morphological traits that can be counted or measured on a Fast Plant.

8 To count the hairs it is easiest to remove the 1 st true leaf with a scissors. Then hold it up close to the hand lens and observe all around the margin of the leaf, counting hairs as you go. When you finish one leaf, record the number of hairs in the GDR Table (Figure 7) at the correct number for that plant. Then go on to the next plant and the next 1 st true leaf, count and record, etc. Pollinating The Fast Plants will begin to flower about 14 days after sowing. When flowers on more than two Fast Plants are open, you should begin to inter-pollinate all open flowers and continue pollinating each day until Day 18 das. Pollen of Fast Plants (rapid-cycling Brassica rapa) is relatively heavy and sticky. Unlike many grass and some tree pollens, Fast Plants pollen is normally not carried in the air. Consider taking photos of your plants at the time of flowering (15-18 das) and also just before harvesting the seed from the plants. (See photo of Fast Plants, 14 das) 1. Pollinate with beesticks made by gluing a dried bee to the end of a toothpick (Figure 9). Making Beesticks Add a drop of glue to affix a bee to a toothpick. Push toothpick into the top of the thorax (middle section) of the bee. thorax only whole bee 2. Collect pollen with your beestick from the anthers of one plant; then move your beestick to the stigmas of other plants. Be sure to deposit a good load of pollen on the stigma of each flower. (Fast Plants are selfincompatible: that is, each stigma prevents germination of its own pollen.) If you don t have dried bees, try using pipe cleaners, cotton swabs, or very small pieces of cloth, e.g. Let beesticks dry before use. velveteen glued to a toothpick. Figure 9. Making a Beestick 3. Stop pollinating on 18 das. Count and record on each of the three GDR Tables the number of flowers pollinated for each of the 12 plants in each nutrient level. Terminate flowering by pinching off all unopened flower buds at the tip of the stem and on any side shoots. 4. After terminating flowering, record the height of each plant in mm, measuring from the soil level to where the terminal buds were removed. Count and record the number of leaves and small leaf-like structures (only those associated with flowers) on the main stem of each plant, including the cotyledons. Do not count leaves on side shoots. 5. Continue to keep the reservoirs full. The plants will need nutrient solution for another 20 days after the last flower is pollinated, so it is important to note the date of the last pollination and termination of flowering. 8

9 Harvesting days or more after the final pollination the lower leaves of the plants will be withering, and pods will be turning yellow. (Inside the pods, the seed coats will be turning brown and beginning to ripen.) At this point, remove the nutrient solution from the reservoir and allow plants to dry until crispy brown (approximately 1 week). 2. Carefully harvest one plant at a time by cutting it off at soil level. Take care not to break off the pods. For each plant, record the number of pods showing one or more seeds. Harvest seeds from each plant Figure 10. Photocopy of dried seed pods on 35 day old Fast Plants growth at three nutrient concentrations, 1/32 strength, 1/16 strength, and 1/8 strength. (not actual size, reduced) separately by gently rolling the dry seed pods between your fingers over a tray or bowl. (Alternatively, you can drop seeds onto adhesive tape which is taped to a card with the adhesive side up.) 3. Count and record the number of seeds harvested for each numbered plant. Count only plump seeds that you think will germinate. Do not count tiny, shriveled seeds as these are not truly seeds. Note: as you harvest your seed, are there observable differences among the seeds from different plants, or from different treatments? Do you have any questions about this? Optional: After recording the seed counts for each plant, if you want to save the seeds from each of the three treatments for further experimentation, place the seeds in labeled envelopes. Include: the nutrient treatment level ; the number of plants that produced the seeds; date of harvest; total number of seeds produced; your name. 4. Store seed envelopes in a cool, dry place, e.g. in a refrigerator in a moisture-proof, sealed container. Ideally, the container would also contain a drying compound, e.g. indicator silica gel, which can be obtained from a pharmacist or from a camera store. Seed that is stored dry and cool will remain viable for over 10 years. Congratulations! In your three GDR Tables, you now have important sets of recorded experimental data from which to make some calculations and which can be used to evaluate the original hypothesis. 5. On the separate GDR Tables for each nutrient treatment you should complete the summary statistics for each trait that you have measured. Then transfer these calculations (statistics) to the GDR Summary Table, Table 2 (Figure 11). Under each trait, record the number of plants, n, that you observed, measured and recorded. Usually n will be 12 unless one or more plants are missing. Then calculate the average, x, for each trait. (x = sum of all measures for trait divided by n, the number of plants measured.) x is sometimes called the mean. Finally, calculate the range, r, of variation in measurements. (r = highest number minus lowest number) Optionally, if you have a statistical calculator, you might wish to calculate the standard deviation, s. (s is an estimate of the average amount of variation around the mean.) Highly variable traits have higher s values than traits with low variation. 9

10 6. Review carefully the actual measurement data recorded in each of the three GDR Tables for each trait noting the variation among numbers. At the same time review your summary statistics of the data. Do you understand how the statistics summarize and represent the actual data? Now review and compare the summary statistics for each trait for each of the three nutrient treatment levels. There is a great deal of information here, but do not be daunted! Before you analyze your data, draw conclusions and ask more questions, you should display your summary data graphically using the graphs provided. From your summary statistics, graph the average responses for each of the five traits you measured on the y axis (vertical axis) of a graph as a dependent variable in relation to each of the three nutrient treatment levels (independent variable) that your plants grew under on the x axis (horizontal axis). You should plot each trait on a separate graph. Figure 11. GDR Summary Table Table. Summary data from Paul Williams' research notebook. (Effect of Nutrition on Fast Plants Growth, Development and Reproduction data) In order to visualize the extent of variation of each trait around the mean (x) you should also indicate where the high and low measures representing the range,r, also lie on the y axis. Optionally you might also note the positions of the standard deviation,s, above and below each mean, x. Analysis and questions As you summarize and graph the data from your experiment you will notice that some traits of the growing plant are affected by the nutrient environment more than others. From this knowledge you should be able to evaluate the hypothesis, More food (nutrient) is better for seed production. Is this really the case? Are you really sure? What if you increased the nutrient from 1/8X to 1/4X or 1/2 X; would you continue to increase seed production? Is there a point where too much nutrient is detrimental to plant growth and seed production? From your data you also have evidence that demonstrates that some developmental traits such as leaf number on the main stem and average number of hairs on the margin of the first true leaf are not as strongly influenced by environment as are number of flowers and seeds produced. You might also notice that of the two developmental traits, leaf and hair number, that hair number was much more variable from plant to plant in the population than was leaf number. From these observations come many questions of importance to understanding the relative contributions of environment and heredity to the individual. Can you think of what some of these questions might be? One such question on the inheritance of hairs is addressed in the next activity, Creating the Wooly Booger, Hairy s Inheritance. Extensions 1. What is the final consumption of nutrient solution by each set of plants? Did the larger plants consume more water than the nutrient 2. Can you estimate the nutrient uptake by the plants? 10

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