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Activity 7 - Effect of Environment on Plant Growth

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  Share  Activity 7: Effect of Environment on Plant Growth The purpose of this activity is to demonstrate the effect of changes in theenvironment on the growth and fertility of landscape grasses and crop grassessuch as wheat and rice. You will place the plants in environments such as highsalinity, cold, heat, or drought and observe the different reactions of the plants tothese conditions. Students will compare the growth of treated plants to that of thecontrol plants which are grown under optimal conditions. You will then discussthe desirability of breeding new types of plants that are better able to withstandthese changes if they occur in the general environment. Objective 1. To plant, grow and maintain plants under different environmental treatmentconditions.2. To observe differences in plant growth between these treatments.3. To compare the growth of treated plants with the growth of control plants.  Background Breeding plants that are able to survive in different environmental conditions or when attacked by diseases or pests has occur r ed for thousands of years as people gradually domesticated the plants that they needed to use for food or asornamentals. Generally this breeding involved identifying a trait in another relatedspecies that could then be used as the donor of this trait to the domestic plantthey wished to improve. In traditional plant breeding, the two species would becrossed either naturally or artificially to produce a hybrid plant that containedgenes from both parents. These hybrids were screened to see which of themcontained the gene for the trait of interest. The selected hybrids werebackcrossed to the domestic parent over many generations with selection ateach step for the trait of interest. This ultimately results in a new plant thatcontains DNA mainly from the srcinal domestic parent but also a small amountof DNA from the donor that encompasses the gene that we desired to transfer. As you can imagine this procedure is very expensive and time consuming and itis many years before a new plant is ready to be released to the generalpopulation. A second drawback with this procedure is that there is inevitablysome DNA present in the new plant that arose from the donor parent that maynot be desirable. A second method of breeding involves the use of biotechnology. Some of thelaboratory techniques that you have learned in this program in the activities DNAextraction, restriction digestion, plant tissue culture, transformation and PCR areutilized in this type of breeding. The gene for the trait that we are interested inmay be identified in either a related species or even a totally different genus or family. For instance a gene from a fish that is able to survive in very coldconditions has been bred into soybean so that the plants are now able to survivein much colder environments than the srcinal soybean. The specific DNA thatcontains just the gene of interest can be cut out of the donor organism's DNA, Lessons andLabs Plant Biotech Activities HomeWhat is DNA?DiseasesHistoryHealthEnvironment ActivitiesConclusions  APS > Education > K-12 > Lessons and Laboratories > Classroom Activities in PlantBiotechnology > Activity 7 - Effect of Environment on Plant Growth  cloned and prepared for insertion into the recipient plant. Transformationprocedures are utilized to move the gene into the recipient and new plants aregrown in tissue culture before moving into the greenhouse and the field.Selection methods are used during tissue culture to select only plants that havethe new gene in their cells and thus these are the only ones that continuethrough the whole procedure. Once plants are mature enough to be planted inthe field or greenhouse some of the more traditional methods of plant breedingare used to increase the number of plants, to test that the gene functionscorrectly under the relevant conditions, to determine if the new gene is stablyinherited and, most importantly, to check that the new plants do not have adetrimental effect on either the environment or other plants and organisms.  Materials 25 germinated seeds of wheat or rice16 10-cm (4 ) potsPotting soil/peat moss mixed 1:15 small containers to hold pots Aquarium or other clear container with lid or topTable salt (NaCl)Scale to weigh NaCl1-liter measuring cylinder, volumetric flask or kitchen measuring jugFull spectrum grow-lights if necessaryUse of refrigerator or cold room  Procedure Note:  The seeds must be germinated and planted at least 5 weeks beforebeginning the experiment. If you only want your students to see the results of thetreatments, then you should begin at least 7 weeks before the class period is tooccur.1. Germinate 15-20 rice seeds by first washing in 10% bleach for 5 minutesand then rinsing 3 times in sterile distilled water. Place the seeds in a petridish that has a filter paper in the bottom. Moisten the filter paper with steriledistilled water until it is very wet and place in a warm area, preferably anincubator set at 28°C or in an area that is warmed by the sun. Seed shouldgerminate within 5-7 days. 2. Plant one seed per 4” pot that is filled with potting soil mixed with equalparts of peat moss. Gently cover the seed until just the top part of thecoleoptile (shoot) is visible. Water well and place in a well lit, warmenvironment such as an incubator or a warm windowsill (but protect fromany cold drafts). Keep moist. 3. Make sure that the plants receive at least 12 hours of light per day. (If youare using rice seeds, once the new plants have begun to fully emerge after about 10 days, the pots can be placed into a container so that floodirrigation can begin. Flood irrigation involves filling the container with water until it is about 1/3 of the distance up the side of the pots. About once per week a small amount of fertilizer (follow the directions for potted plants for whichever fertilizer you choose) should be added to the water used to refillthis container. The solution in the container should be completely changedevery week before the fertilizer water is added and then topped up duringthe rest of the week). Wheat seedlings should be watered daily to maintainconstant moisture in the soil, and fertilizer should be added about once per week. 4. When the plants are 5 weeks old you can begin the environmental stressdemonstration.5. Choose the ten best plants that are of approximately the same height andwith the same number of leaves. The remaining plants can be discarded or kept for backup if something goes wrong with one of the treatments.  6. Two of the plants will be control plants that will continue to be floodirrigated, with fertilizer added once every week. Make sure that the plantshave at least 12 hours of sunlight or artificial full spectrum “grow-lights” per day. 7. Separate the remaining eight plants into four groups so that there will betwo plants for each treatment. Label two pots “drought”, two pots “cold”, twopots “saline” and the remaining two “heat”. All pots should be placed incontainers so that irrigation can continue during the treatment asnecessary. Each treatment will last for 5-14 days, depending on theresponses you have in your classroom situation.Treat as follows:1. DROUGHT  - Maintain these plants in the same environment as thecontrol plants but do not add any water to the container for 3 days.This will allow the pots to dry out at which point the drought treatmentwill begin. Do not irrigate for a further 5 days. Irrigate normally for 2days and then repeat the drought treatment for another 5 day cycle.2. COLD  - Place these plants in a refrigerator or other cold room(<10°C) for 10-14 days but continue to provide light, water andnutrients as for the control plants 3. SALINE  - Make a 100 mM NaCl solution + to use for irrigation. Thisshould provide a solution that has a conductivity of approximately 10-12 dS/m). Irrigate the plants constantly with this solution for 14 daysbut be sure to keep all the other growth conditions the same as thoseof the control plants. 4. HEAT  - Place the plant inside an aquarium or clear plastic container,cover and place on a warm windowsill or under grow lights. Thetemperature in the enclosed container needs to rise to above 35°C.Keep all other environmental conditions the same and be careful notto release too much heat from the container when you are changingthe irrigation solution. Grow the plants in this environment for 14days. 5. CONTROL  - Keep these plants in the same environment as theywere, making sure that there is still at least 12 hours of daylightand/or supplemental artificial light. The plants should remain floodirrigated and treated with fertilizer each week until the end of theexperiment. + You can have the class work out how to make this solution as part of achemistry or mathematics lesson. A 1Molar solution contains 1 mole of thesolute dissolved into 1 liter of water. 1 mole of NaCl contains 58.44 gramsi.e. number of grams equivalent to the formula weight of NaCl. So, to make100 mM we need to take 58.44/10 grams of NaCl. (100mM = 1M/10 or 1000mM/10). So you need to dissolve 5.844 grams of NaCl in water andthen make the volume up to 1 liter for each liter of saline solution that your container will hold.8. Have students record their observations. Note height of plants, number of new leaves, degree of wilting, color of leaves, and any other symptomssuch as spots on leaves, browning of leaf tips, for example. When all thetreatments are complete and observations noted, you may remove theplants from the pots, wash the roots carefully and measure the length of theroots. 9. Have students complete the activity sheet.Examples of expected results:  ControlSalineDroughtColdHeatControlSalineDroughtColdHeat  Some other questions to have students consider:What do you think are important tools for improving our ability to feed the world? Are there technologies that you think should not be used?Find out how you could become a scientist who has the power to changechildren’s lives by providing growers with the tools to grow nutritious foodnecessary for the healthy development of our children.  Student Activity: Effect of Environment on Plant Growth 1. Inspect all of the plants that your teacher has prepared for thisdemonstration and record your observations in the chart below. Recordseparate information for each of the two plants in each treatment and eachof the controlsTreatmentPlantheightNo. of leavesWilting?Yes/NoColor of leavesOther stresssymptomsRootlength
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