* Readily available from supermarkets and health food stores minutes (total over 3 to 7 days) SOSE: Investigate Australia s salinity crisis

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1 Lesson Plan 12 Salt and germination Brief description This fascinating, cheap and very reliable experiment clearly demonstrates the damaging effects of salinity (salt) on seed germination. Mung beans are germinated on paper towels in takeaway containers using various concentrations of salt water. The activity captivates student interest and results are clearly visible within three days. Use it as part of a unit on plants or Australia s salinity crisis. * Readily available from supermarkets and health food stores Duration: Year level: Topics: Preparation: Extensions: minutes (total over 3 to 7 days) Lower to upper primary Plants, germination, salinity 10 to 20 minutes SOSE: Investigate Australia s salinity crisis Overview SESSION 1: DISCUSSION AND PREPARATION (50 70min) Introduce the experiment Discuss procedure Prepare salt solutions Distribute materials and prepare Petrie dishes Add mung beans to Petrie dishes and store in cool location OBSERVATION SESSIONS (over 3 to 7 days) (10 15min) Record the number of beans that have sprouted Record any other observations that can be made CONCLUDING SESSION (20 30min) Record the number of beans that have sprouted Record any other observations that can be made Analyse the and present the results using age appropriate instruments (eg tables, graphs, posters) Lesson 12 Germination Experiment Page 1

2 Materials and equipment Qty / Student Description 20 1 Mung beans (dry) 1 2 Round takeaway container (lid optional) 2 Paper towels 1 Cling wrap (~ 15 cm piece) 1 Rubber band 1 Packet of salt 1 3 Distilled water for salt solutions 1 Measuring jug or beaker 1 Plastic cup 1 Eyedropper for adding salt solution 1 Kitchen scales for measuring salt 1 Tweezers (shared) 1 Magnifying glass (shared) 1 One 500 gram packet of dry beans is sufficient for the whole class available from health food stores and some supermarkets 2 Small and large containers are suitable 3 Salt solutions prepared by teacher or group see Teacher Notes Page 7 Preparation Purchase mung beans from supermarket or health food store. Collect sufficient quantities of takeaway containers, plastic cups etc listed in the table above. Decide how you will allocate salt solutions to each students (see Teacher Notes P. 8). Lesson 12 Germination Experiment Page 2

3 Objectives Students prior knowledge No prior knowledge is required or assumed for this lesson plan. The objectives listed below are suggestions only and may not be appropriate for every year level. Science skills Students will: Carefully prepare and label a Petrie dish (takeaway container) for the germination experiment Carefully add salt solution and mung beans to Petrie dish Observe the mung beans over several days Record their observations using a table in their science journal Infer that high concentrations of salt prevent seeds from germinating Science concepts Low concentrations of salt are naturally present in soil and water High concentrations of salt are naturally present deep underground in Australia European farming practices, which removed or replaced native plants with crops that have shallow roots, have raised groundwater and brought salt to the surface High concentrations of salt in the soil or water prevent seeds from germinating and plants from growing Seawater has a salinity of approximately 3.5% (approximately 35 grams of salt per kilogram of seawater) Positive attitudes Students will Develop an appreciation of and concern for the environment and the environmental impact of farming practices Develop a sense of wonder about the amazing process of plant germination and growth Develop an understanding of and appreciation for the scientific method in investigating real life problems Work cooperatively with partners/group members and ensure handle all equipment and water carefully and responsibly dispose of waste responsibly (eg pour waste water onto plants or garden beds instead of down the sink) Lesson 12 Germination Experiment Page 3

4 Procedure SESSION 1 DISUCSSION & PREPARATION (50 to 70 minutes) Introduction Whole Class (10 15 min) Discuss the salinity crisis in Australia see Teacher Notes (P 10) for a brief introduction and / or: Distribute dry and soaked mung beans (two each per student) to observe and lead a discussion about germination and the life cycle of seeds. Students will observe a scar and tiny hole in the mung bean seed coat. Discuss the amazing fact that each mung bean seed contains all the energy and instructions required to create a whole new mung bean plant which, under the right conditions, will grow and produce more mung beans. Discuss the objectives of the Mung Bean Germination experiment to determine the amount of salt mung beans can tolerate before failing to germinate. You could use the discussion to develop the procedure together with the class by asking leading questions such as: how could we find out how much salt mung beans can tolerate? how much salt should we use? can we use plain old tap water? does it have any salt already in it? Each student will prepare a Petrie dish with paper towel, salt solution and mung beans. Failure of a seed to germinate is just as important as a successful germination. Prepare salt solutions as a demonstration Whole Class (10 15 min) Students will appreciate just how the tiny the quantities of salt the mung bean seeds can tolerate if they see the actual amount of salt being added to the water, so if possible, perform it as a demonstration you can involve them in the calculations by writing them on the whiteboard or simple by discussing each step. Using the kitchen scales, plastic cups, salt and distilled water, prepare salt solutions of various concentrations for the class to use discuss the procedure and perform calculations together with the class if appropriate (see Teacher Notes P 6 for details) Allocate groups, discuss safety issues and distribute worksheets and materials Prepare Petrie Dishes Individual Groups (20 25min) Group manager collects materials Investigate dry and soaked mung beans with magnifying glass to identify parts Each student prepares a Petrie dish with paper towel and a label Moisten paper towels Place beans on paper towel Store beans in a bright, cool place away from direct sunlight Conclusion Whole Class (10 15 min) Discuss student predictions set science journal writing tasks Lesson 12 Germination Experiment Page 4

5 Procedure continued OBSERVATION SESSIONS (3 to 7 days 10 to 15 min each) Observe and record results at approximately the same time every day students will be very keen to check progress often so it is worth discussing the importance of recording the results at the same time (ie regular intervals) Each student counts the number of beans that have sprouted in the Petrie dish they prepared and records the number in their science journal CONCLUDING SESSION (20 30 minutes) Once all the results have been recorded, calculate the average number of beans that have sprouted by the end of each day (the results are easier to interpret if the total numbers sprouted are recorded everyday eg if three have sprouted on day 1, record 3 / if 6 more sprout the following day record the new total of 9) Calculate the averages for each salt concentration tested (if appropriate, students can perform these calculations if not, perform them on the board) Discuss the results and important observations from the experiment such as: Mung beans will not germinate and grow if water salinity exceeds approximately 0.25% The salinity of seawater is approximately 3.5% so the salt tolerance of mung beans is much less than half that of seawater salinity levels Discuss the experiment and whether the method answered all of the students questions if not, discuss what changes could be made or other ways the questions could be answered, and if possible, follow some or all of these up Lesson 12 Germination Experiment Page 5

6 Teacher s notes Preparing salt solutions Perform this a teacher demonstration for younger students or to economise on time. 1. Equipment and materials: Distilled water Table salt Plastic cups or bottles Accurate kitchen scales Measuring cup (250ml or larger) Small cup (for salt) Teaspoon 2. Measure salt required into cup on scales (see table below for amount to use) If the weight required is less than your scale s smallest increment, measure out 2 or 4 times the amount, pour into a pile and use a spatula to halve or quarter the pile as illustrated. 3. Add salt to measured volume of distilled water and stir Repeat for each of the concentrations required as per table below Amount of salt to add (in grams) to demineralised water (in millilitres) for various salt solutions Salt concentration (c) (by weight*) Grams of salt to add (s) 250ml 500ml Tap 0g 0g 0% 0g 0g 0.25% 0.6g 1.3g 0.5% 1.3g 2.5g 0.75% 1.9g 3.8g 1.0% 2.5g 5.1g 1.5% 3.8g 7.6g 3.5% (equiv. to seawater) 9.1g 18.1g salt to add = concentration weight of water ( 1 concentration) s = c W / ( 1 c ) [* Note: 1 ml of water weighs 1 gram] Lesson 12 Germination Experiment Page 6

7 Preparing Petrie dishes Each student can prepare their own Petrie dish, add a label (see below) and salt solution. Share scissors and pens if necessary. It is advisable to check each Petrie dish before allowing students to add salt solution to ensure labels match solutions added and guarantee clear experimental results. 1. Fold two sheets of paper towel in half two times to produce a square eight sheets thick Use the Petrie dish (takeaway container) to mark a circle on the top sheet 2. Cut paper towel into circle 3. Add label to Petrie dish (see below for suggested label details) Use an eyedropper or pipette to moisten paper towel drain off any excess water Mung Bean Germination Experiment Suggested label information Salt (NaCl) Concentration: Date: Prepared by: Lesson 12 Germination Experiment Page 7

8 Adding Mung Bean seeds 1. Hint: use a flat surface and a playing card or piece of thin cardboard to count and separate beans quickly Use container lids to collect and carry beans to desks 2. Carefully place mung beans on paper towel with tweezers 3. Space mung beans evenly apart on paper towel Allocating solutions 4. Store in a well lit area but away from direct sunlight to avoid towel drying out observe daily for next 4 to 7 days Note: move dishes carefully to ensure the beans do roll around separate any beans that have rolled into each other after moving the container The table below suggests the number of Petrie dishes to allocate to each salt concentration for various total numbers (ie number of students in your class). You could allocate these randomly by drawing them from a box and giving one to each student. Salt concentration Number of Petrie Dishes Class of 18 Class of 27 Class of 30 No water (dry) Tap water % % % % % % % Lesson 12 Germination Experiment Page 8

9 Recording results Mung beans will sprout overnight on moist paper towel and do not necessarily need to be stored in a dark place. Typical results for this experiment are listed in the table and photographs below. Salt Concentration Total beans germinated (out of 20) Day 1 Day 2 Day 3 Day 4 Day 5 Comments No water (Dry) No change by day 5 Tap water % % % % % % Sprouts are up to 5cm long by day 5 Sprouts are up to 5cm long by day 5 Sprouts are up to 5cm long by day 5 Beans sprout but there is very little growth by day 5 Bean coats split but little or no growth Bean coats split but no growth dried out by day 5 Beans coats split but no growth dried out by day 5 3.5% Beans drying out 0.25% Salinity - Day 1 Six beans have sprouted. Sprouts are approx 3 to 6mm long 0.25% Salinity - Day 3 All 20 beans have sprouted. Sprouts are approximately 10 to 35 mm long 1.5% Salinity - Day 3 Beans look very dry 3 of the bean s coats have split but no sprouts have grown Lesson 12 Germination Experiment Page 9

10 Australia s Salinity Crisis Salinity Salt is naturally present in huge quantities below Australia s vast surface. It has built up over many thousands of years through natural processes and native plants have adapted to cope with it. Many native woodland plants have deep roots and consume large amounts of water, preventing water from leaking through the soil and reaching the water table and salt deep underground. Until European farming practices arrived, the salt remained deep underground, well beneath the fertile topsoil from which plants draw their water and nutrients. But crops such as wheat and many others have shallow roots and consume much less water than native plants. The excess water leaks through the soil and eventually reaches the ground water below. Each successive rainfall then raised the water table bringing dissolved salt from deep underground to the surface. Once it reaches and the topsoil, plants can no longer grow and eventually die off. The surface water evaporates leaving large salt deposits. This has already, and is continuing to happen on a grand scale in Australia. These salt concentrations will take many generations to reduce. The problem does not only affect growing plants but also threatens to contaminate drinking water supplies and causes corrosion of buildings, roads, and underground pipes and cables. Altogether, the costs to individuals, communities and Australia s economy are enormous. How water brings salt to the surface To understand how the salinity crisis has arisen, consider a bucket with a layer of salt at the bottom, covered with pebbles and a layer of topsoil as illustrated. If the plants can consume all the water supplied to the bucket before it reaches the pebbles, the salt stays put at the bottom. If the plants are removed or replaced with others, which consume less water, but watering continues at the previous rate, the water will reach the pebbles and eventually, the bottom of the bucket. Each watering adds to the water collecting at the bottom, progressively raising the level. The salt layer will dissolve into this groundwater and rise up with it. Eventually, the level of salty groundwater will reach and contaminate the soil, killing all the plants. Once the soil has been contaminated, the salt is almost impossible to remove. Further information about Australia s salinity crisis: Department of Heritage and Environment Salinity ABC Science Feature Salinity (Our silent disaster) CRC for Plant-based Management of Dryland Salinity pebbles salt plants soil Figure 1 Over-watering dissolves salt and raises it to the surface Salinity Australia s Silent Flood (ABC TV series) Four part documentary examining the threat of salinity, from its ancient origins to future forecasts. The series looks at every state affected and talks to Australia's foremost authorities from the farming, environmental and scientific worlds. Narrated by award winning Australian actor David Wenham and produced by ABC Education's Lifelong Learning in conjunction with Land and Water Australia. Lesson 12 Germination Experiment Page 10