PLANT TISSUE TESTING. Lesson A4 3

Transcription

1 Lesson A4 3 PLANT TISSUE TESTING Unit A. Plant Science Problem Area 4. Managing Inputs for Plant Growth Advanced Life Science Area: Plants and Soils Standard PS.5.9 Evolutionary Trends and Ecology: Discuss the impact of nutrient runoff on various nutrient cycles. Standard PS.6.10 Physical Environment: Soils Formation and Chemistry: Discuss the effects of soil ph on mineral availability and toxicity. Describe the chemical reactions by which lime and sulfur impact soil ph. Student Learning Objectives. Instruction in this lesson should result in students achieving the following objectives: 1 Name the nutrients needed for plant growth. 2 Explain why nutrients are essential to plants. 3 Explain where and how plants can obtain nutrients. 4 Describe environmental conditions that influence nutrient deficiencies. 5 Explain where plants can obtain nutrients if inadequate amounts are present in the soil. 6 Discuss the nitrogen cycle and its affect on plant nutrition. Biological Science Applications in Agriculture Lesson A4 3 Page 1

2 List of Resources. The following resources may be useful in teaching this lesson: Animal, Plant, and Soil Science Lesson Plan Library Unit C. Plant and Soil Science Problem Area 4. Environmental Factors Affecting Plant Growth Lesson 5. Determining Plant Nutrients and Fertility. Danville, IL: CAERT, Inc. Animal, Plant, and Soil Science Lesson Plan Library Unit C. Plant and Soil Science Problem Area 8. Soil Fertility and Moisture Management Lesson 4. Identifying Nutrient Deficiencies in Crops. Danville, IL: CAERT, Inc. Horticulture Lesson Plan Library Unit A. Horticultural Science Problem Area 4. Growing Media, Nutrients, and Fertilizers Lesson 1. Understanding Properties of Growing Media. Danville, IL: CAERT, Inc. Osborne, Edward W. Biological Science Applications in Agriculture. Danville, IL: Interstate Publishers, Inc., Towle, Albert. Modern Biology. Austin: Holt, Rinehart and Winston, List of Equipment, Tools, Supplies, and Facilities Writing surface Overhead projector Transparencies from attached masters Copies of student lab sheets Terms. The following terms are presented in this lesson (shown in bold italics): atmospheric macronutrients autotrophs biogeochemical cycles complete fertilizer cortex denitrification fertilizer filler fixed hydroponics immobilization incomplete fertilizer inoculation legumes macronutrients micronutrients mineralization Biological Science Applications in Agriculture Lesson A4 3 Page 2

3 nitrogen assimilation nitrogen cycle nitrification nitrogen fixation ph plant tissue test primary macronutrients prokaryotes rhizobia secondary macronutrients soil symbiosis translocation Interest Approach. Use an interest approach that will prepare the students for the lesson. Teachers often develop approaches for their unique class and student situations. A possible approach is included here. Show students 3 4 samples of growing plants (greenhouse crops, indoor plants, field crops, or vegetable crops). As a group, the plants should exhibit a variety of plant deficiency or health symptoms, from good condition to obvious nutritional and environmental deficiencies. Ask students to describe the health/condition of each plant. Does the plant show any deficiency symptoms or other problems? If so, what? How can we verify your diagnosis? Be sure to focus on nutrient deficiencies, in addition to other problems students identify. SUMMARY OF CONTENT AND TEACHING STRATEGIES Objective 1: Name the nutrients needed for plant growth. Anticipated Problem: What are the nutrients needed for plant growth? I. Plants need a variety of nutrients in order to survive and carry on the necessary metabolic processes of life. Plants require water, carbon dioxide, oxygen, and a variety of essential minerals in order to survive. A. About 80 85% of the weight of a fresh plant is water. The remaining part of the plant contains elements that are absorbed through the roots and used for plant growth. Biological Science Applications in Agriculture Lesson A4 3 Page 3

4 B. Plants receive most of the nutrients that they need from the growing media, or in the case of hydroponics, the nutrient solution that the roots are exposed to. In order to maintain healthy plants, a grower must provide the right type and amount of nutrients to the media so that the plants can absorb the nutrients and grow. C. Plant nutrients can be divided into two groups, macronutrients and micronutrients. D. Macronutrients are needed in large quantities and include atmospheric, primary, and secondary elements. 1. Carbon, hydrogen, and oxygen make up about 90 95% of the weight of the dry matter. These three atmospheric macronutrients are nonminerals. Plants acquire carbon, hydrogen, and oxygen from carbon dioxide (CO 2 ) and water (H 2 O) through the process of photosynthesis. The rest of the dry weight is made up of minerals. 2. The primary macronutrients are nitrogen (N), phosphorus (P), and potassium (K). 3. The secondary macronutrients include calcium (Ca), magnesium (Mg), and sulfur (S). E. Those nutrients that are needed in smaller or trace amounts by the plants, but are still essential to plant growth are called micronutrients. The micronutrients are boron (B), copper (Cu), chlorine (Cl), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn). F. A soil test can be performed on the soil or a plant tissue test can be performed using the tissues of a plant to determine which nutrients are present or deficient (absent or lacking). When nutrients are deficient in the soil, the plant growth is adversely affected. Oftentimes, plants visibly show a nutrient deficiency by turning colors. When nitrogen is deficient in the soil, a plant s older leaves will start to turn yellow (chlorosis) and eventually die. A plant will show purpling in the stem or leaf when phosphorus is deficient in the soil. Burning or scorching of the leave s margins may indicate a potassium deficiency. G. Because macronutrients are needed in larger quantities they are usually the ones that are the most limiting to plant production and thus are the ones that producers will add to their crops. H. Mnemonics (pronounced ni-mon-iks) is the art of improving the memory using a formula. A mnemonic formula has been developed to aid in recalling all sixteen elements. Carbon (C), Boron (B), Hydrogen (H), Oxygen (O), Phosphorus (P), Potassium (K), Nitrogen (N), Sulfur (S), Calcium (Ca), Iron (Fe), Magnesium (Mg), Chlorine (Cl), Manganese (Mn), Molybdenum (Mo), Copper (Cu), Zinc (Zn). The following mnemonic can be used to help remember the sixteen elements: C. B. HOPKiNS CaFÈ Mighty good Closed Monday Morning See You Zen. Use TM A to illustrate plant nutrition. Students could come up with their own mnemonic to help them remember the macronutrients and/or micronutrients. Biological Science Applications in Agriculture Lesson A4 3 Page 4

5 Objective 2: Explain why nutrients are essential to plants. Anticipated Problem: Why do plants need nutrients? II. In order to be considered essential, an element must meet the following criteria: (a) absence of the element results in abnormal growth, injury, or death; (b) the plant is unable to complete its life cycle without the element; (c) the element is required for plants in general; and (d) no other element can serve as a complete substitute. Nutrient Element Forms Absorbed Function in Plants Deficiency Symptoms Nitrogen (N) NO 3- or NH + 4 Constituent of amino acids (and thus, proteins and enzymes); constituent of chlorophyll (four N atoms in each molecule); stimulates carbohydrate utilization; stimulates root growth and development; regulates uptake and utilization of other nutrients Phosphorus (P) H 2 PO 4- or HPO 2-4 Component of ATP (adenosine triphosphate), which implements energy-using processes in plants; component of DNA and RNA; used in proteins, metabolic transfer processes, photosynthesis, and respiration; affects cell division, root development, maturation, flowering and fruiting, and overall crop quality Potassium (K) K + Activates enzymes; regulates opening and closing of stomata; regulates water uptake by root cells; essential for photosynthesis, starch formulation, and translocation of sugars; aids in nitrogen metabolism; promotes growth of meristem tissue Sulfur (S) SO 2-4 Essential component of amino acids and vitamins Stunted and slow growth; yellowing of lower leaves of plant; poor root system Purpling of the stem, leaf, or veins on the underside of leaves; stunted growth and maturity; reduced yields due to decreased seed and fruit formation; poor root system Burn or scorch of margins of leaves, particularly older leaves; lodging; decreased yields; lack of disease resistance; decreased crop quality Yellowing of leaves, light green leaves, slow growth; looks similar to nitrogen deficiency symptoms Biological Science Applications in Agriculture Lesson A4 3 Page 5

6 Nutrient Element Forms Absorbed Function in Plants Deficiency Symptoms Calcium (Ca) Ca 2+ Component of cell walls, needed for cell growth and division Magnesium (Mg) Mg 2+ Needed in chlorophyll, used in vitamins and amino acids, used in fat and sugar formation, needed for seed germination Boron (B) BO 3- or B 4 O 2-7 Affects pollen germination, cell division, metabolism of nitrogen, fruiting, water regulation, and hormone movement Copper (Cu) Cu 2+ Part of enzymes, used in chlorophyll synthesis, catalyst in respiration, protein, and carbohydrate metabolism Chlorine (Cl) Cl - Helps in shoot and root growth Iron (Fe) Fe 2+,Fe 3+ Found in enzymes, helps to form a variety of compounds, catalyst in chlorophyll synthesis Manganese (Mn) Mn 2+ Helps synthesize chlorophyll, serves as a coenzyme Molybdenum (Mo) MoO 2-4 Used in protein synthesis, needed for some enzymes Zinc (Zn) Zn 2+ Forms chloroplasts, auxins, and starch, needed by legumes for seed development Terminal leaves may be deformed, stunted root growth, dead spots in midribs, black color to plant Yellowing between veins and leaves may droop Death of terminal buds, thickening of leaves, leaves curl and die, lateral buds grow and then die Death of terminal leaf buds, yellowing between veins, slowed growth Wilting of plants, yellowing, leaves turn bronze Yellowing or light green in leaves, yellowing between veins Light green between green veins, leaves then turn white Causes nitrogen deficiency and thus similar signs Roots are abnormal, yellowing between veins, leaves become bronzed or mottled Plant Nutrient Requirements Name Symbol Ionic form Ionic Name Macronutrients Primary Nitrogen N N0 3 ;NH 4 + Nitrate, ammonium Phosphorus P HPO; 2,H 2 P0 4 Orthophosphates Potassium K K + Secondary Calcium Ca Ca +2 Magnesium Mg Mg +2 Sulfur S SO4 2 Sulfate Biological Science Applications in Agriculture Lesson A4 3 Page 6

7 Plant Nutrient Requirements Name Symbol Ionic form Ionic Name Micronutrients Boron B B0-2 4 Borate Copper Cu Cu +2 Chlorine Cl Cl - Chloride Iron Fe Fe +2,Fe +3 Ferrous, ferric Manganese Mn Mn +2 Manganous Molybdenum Mo MoO -2 4 Molybdate Zinc Zn Zn +2 Use TM B, TM C, and TM D to show the importance of essential nutrients to plants. Hand out LS B showing the functions and deficiency symptoms of N, P, and K or hand out LS C to students if desired to show the functions and deficiencies of both macronutrients and micronutrients. Conduct the Plant Tissue Testing Experiment (LS A). Objective 3: Explain where and how plants can obtain nutrients. Anticipated Problem: Where do plants obtain nutrients and how do they absorb the nutrients? III. Nutrients are supplied through the growing medium or nutrient solution. Plant analysis can provide very valuable information to the grower as they make management decisions. When asked what plants need to grow, most people would respond with water, sunlight, and soil. In all actuality, soil is only one type of media that can be used to grow plants. There are a number of substances that allow plants to grow. A. Soil is the outer portion of the Earth s crust that supports plant growth. Soil contains air, water, minerals, and organic matter. B. A Soilless medium (one that contains no topsoil) can be used to grow plants since plants need the minerals and water from the medium. Examples include perilite and vermiculite. C. Hydroponics is a method of growing plants in a nutrient solution. The plants in a hydroponics unit could be supported in a sand or gravel substrate for support or the roots could be left bare. With bare roots, the plants root system can float in the nutrient rich solution, or the nutrients could be sprayed directly onto the roots. D. These essential minerals are dissolved in a water or aqueous solution. This solution moves from the soil or surrounding environment through the root into the xylem. Translocation is the movement of organic molecules throughout plant tissues. Most of the water and nutrients are absorbed through the root hairs. With the help of adhesive and cohesive properties of water, the solution moves upward against the force of gravity Biological Science Applications in Agriculture Lesson A4 3 Page 7

8 to the various parts of the plant usually the leaves. Most of the water is lost through transpiration via the stomata. This also aids in the movement of water from the roots to the rest of the plant. Metabolic processes use the nutrients for a variety of purposes. Use TM E to review the content of this objective. Conduct soil tests using soil samples from some of the plants used in the tissue testing process. Compare the results. Objective 4: Describe environmental conditions that influence nutrient deficiencies. Anticipated Problem: What environmental conditions influence nutrient deficiencies? IV. Understanding environmental conditions and their effects on the crop can help pinpoint a problem that is developing. All factors that influence crop growth, response to fertilization, and yield should be evaluated. A. The measure of alkalinity or acidity of a substance is known as ph. The ph scale runs from 0 to 14, with 0 being extremely acidic, 7 as neutral, and 14 as extremely basic. 1. Changes in ph can be made by adding sulfur or gypsum to lower ph (make more acidic) and by adding limestone to increase ph (make more basic). Generally plants grow best within the ph range of 5.5 to The ph value of soil is important to agriculturists because certain nutrients become unavailable to plants if the ph value is too high or too low. The amount of nitrogen, phosphorus, and potassium that are available is dependent upon soil ph. B. The soil must be of good tilth and permeable enough for roots to expand and feed extensively. A crop will develop a root system 6 feet or more in depth in some soils to get water and nutrients. A shallow or compacted soil does not offer this root feeding zone. Wet or poorly drained soils result in shallow root systems. C. Cool soil temperature slows organic matter decomposition. This lessens the release of nitrogen, sulfur, and other nutrients. Nutrients are less soluble in cool soils, and that increases deficiency potential. Phosphorus and potassium diffuse more slowly in cool soils. Root activity is decreased. D. Acid soil conditions reduce the availability of calcium, magnesium, sulfur, potassium, phosphorus, and molybdenum, and increase the availability of iron, manganese, boron, copper, and zinc. E. Insect damage is often mistaken for deficiency symptoms. Examine roots, leaves, and stems for insect damage that may look like or may induce a nutrient deficiency. F. Close study will show the difference between plant disease and nutrient deficiency. G. Dry soil conditions may create deficiencies such as boron, copper and potassium. Drought slows movement of nutrients to the roots. H. Soluble salts and alkali are problems in some areas. They may cover only part of the field. They are usually present where a high water table exists, where salt water contamination has occurred, or where poor quality water has been used for irrigation. Biological Science Applications in Agriculture Lesson A4 3 Page 8

9 I. Herbicides and mechanical controls are more important today than ever before. Weeds rob crop plants of water, air, light, and nutrients. Some weeds may even release substances that inhibit crop growth. J. Some soils develop hardpans (compaction) and require deep tillage. This requires more phosphorus and potassium to build up fertility. K. Row width, spacing of plants in the row, and number of plants per acre have important effects on yields. L. Irrigation water can contain nitrate, sulfate, boron, potassium, bicarbonate, chlorine and other salts. A water analysis should be used to modify production practices for utilization of various water sources. M. Other pollutants can also cause nutrient deficiencies as well as other problems. Use TM F and TM G to reinforce the role of ph in plant health. Objective 5: Explain where plants can obtain nutrients if inadequate amounts are present in the soil. Anticipated Problem: If insufficient levels of nutrients are found in the soil, where do the plants get the nutrients that they need? V. Plants need nutrients to grow, but sometimes insufficient amounts are present in the soil. Without the presence of nutrients in the growing media, the plant may grow poorly, showing stunted growth, unhealthy coloring of the leaves, and may be more prone to disease and insect problems. A. Nutrients may become depleted by growing crops. Since crops are harvested, the organic matter does not break down and return to the soil to replenish the nutrients. Additionally, nutrients might leach or run out of the medium via water, causing the grower to continually add the nutrients. The nutrients can sometimes be present in the growing medium, but they are not available for the plants to take up into their roots because the ph level in the soil is not conducive to plant growth. Plants have different ph requirements. B. As a result, growers must add artificial fertilizers, manure, or other organic matter to the soil or nutrient solution for the plants to use. Soil or plant tissue tests should be conducted before fertilizers are added. 1. A fertilizer is any material that is provided to plants to supply the nutrients needed for plant growth. Fertilizers vary in the components they contain, the way they are applied, and the function they serve. 2. When choosing a fertilizer to use, one should always look for the fertilizer analysis on the bag or box. The fertilizer analysis states the percentage of primary nutrients (nitrogen, phosphate, and potash) present in the fertilizer. The analysis is written as 3 numbers, for example, ( ). The numbers, always in this order, represent the percent of nitrogen, phosphorus, and potash, present in the fertilizer. So the Biological Science Applications in Agriculture Lesson A4 3 Page 9

10 example above has 15% nitrogen, 10% phosphate, and 6% potash. Fillers are made up of the remaining essential plant nutrients and are used to ensure a more even application of the fertilizer. The amount of filler in the above example can be calculated: 100-( ) = 59. This means that 59% of the fertilizer is filler. 3. If a fertilizer contains all three primary nutrients, it is called a complete fertilizer. If a fertilizer is lacking any of the three primary nutrients, it is an incomplete fertilizer. C. Local fertilizer and horticulture companies employ specialists that can help in determining an appropriate nutrient program based on your varying conditions. D. Remember that high yields are not the only goal of a plant nutrition program, but that overall quality and economics play vital roles as well. Use TM I to illustrate the importance of fertilizers. Students could conduct the tissue testing experiment on some plants and then fertilize them. Wait at least two weeks and then conduct the tissue test again. Compare the results. Objective 6: Discuss the nitrogen cycle and its affect on plant nutrition. Anticipated Problem: What influence does the nitrogen cycle have on plant nutrition? VI. Nitrogen is a major requirement for plants to grow rapidly and maintain a healthy green color. Although the atmosphere is 78% nitrogen gas, it is the most common nutrient deficiency seen in plants. N 2 gas contains a triple bond which is extremely hard to break; this makes the molecule almost inert. Nitrogen fertilizer is expensive to produce and is thus an expensive input for farmers. Leguminous crops are able to use atmospheric nitrogen rather than rely on the application of fertilizer; this is an important factor in planning a sustainable agriculture program. A. The nitrogen cycle is the recycling of nitrogen as it moves between the abiotic (non-living) and biotic (living) parts of the environment. The largest proportion of nitrogen at any given time is found in the biomass or in dead organisms. 1. Every nutrient that an organism uses is recycled throughout the ecosystem. These cycles are referred to as biogeochemical cycles. The water cycle is another wellknown example of this process. The phosphorus and potassium cycles act in a similar manner. 2. The key concept is that no element is lost or consumed in the environment, but rather it changes form and moves between the abiotic and biotic components of the environment and is recycled. B. Nitrogen is essential to all living organisms because of its use in the synthesis of enzymes, proteins, and chromosomes. In plants, nitrogen is an important component of chlorophyll. C. Plants absorb nitrogen as inorganic nitrate ions (NO 3- ) and in a few cases as ammonium (NH 4+ ) or amino (NH 2+ ) ions. Biological Science Applications in Agriculture Lesson A4 3 Page 10

11 1. The positive charge of ammonium causes it to easily bond to clay soils making it unavailable. 2. The negative charge of nitrate causes it to easily leached away; this can become a cause for water contamination. High nitrite levels in water can cause illness especially in children. 3. Nitrogen that is absorbed by the plant is reduced to N 2-,NH - or NH 2 which then is synthesized into more complex compounds and amino acids and proteins. 4. Nitrogen assimilation is the incorporation of nitrogen into organic cell substances by living organisms. D. Most natural soil nitrogen is in the organic form meaning that it is combined in some manner with carbon. Manures, decomposing organic matter, and urea are all forms of organic nitrogen. These must be oxidized before plants can use them. 1. The transformation of organic matter to the inorganic or mineral form (NH 4+, NO 2-, or NO 3- ) is called mineralization. 2. Immobilization is the conversion of nitrogen from an inorganic or mineral form to an organic form. This process occurs naturally during initial decomposition or nitrogen can be immobilized during chemical fertilizer composition to make it available to the plant at a later time. E. Nitrogen fixation is the conversion of atmospheric nitrogen into oxidized forms that can be assimilated by plants. 1. A symbiotic relationship that exists between bacteria and legume plants is utilized to convert nitrogen gas (N 2 ) to ammonium ions (NH 4+ ) that are usable to plants. 2. Certain blue-green algae and bacteria are capable of biochemically fixing nitrogen. 3. Legumes such as beans, peas, alfalfa, clover, chickpea, and soybeans are able to take in the nitrogen through their roots. Legumes are plants that are members of the family Leguminosae; they have the characteristic capability to fix atmospheric nitrogen in nodules on their roots with the aid of certain bacteria. 4. Aquatic ferns and Gunnera macrophylla (tropical plant) form symbiotic relationships with blue-green algae to attain their nitrogen. Acacias, mesquites, alder, buckthorn, Casuarina, and paloverde plants also rely on bacteria. Lichens form a relationship with cyanobacteria which enables them to be one of the first organisms seen in primary succession. Cyanobacteria also aid the water fern Azolla and cycads. 5. Azotobacter, Beijerinckia, Klebsiella (some), Cyanobacteria (some), Clostridium (some), Desulfovibrio, Purple sulphur bacteria, Purple non-sulfur bacteria, and Green sulphur bacteria are free living nitrogen fixing organisms. Those that form symbiotic relationships with other organisms include Rhizobium, Frankia, and Azospirillum. a. All nitrogen fixing organisms are prokaryotes. b. Prokaryotes are one celled organisms that lack membrane bound organelles and a central nucleus. 6. Rhizobia are aerobic bacteria that are naturally found in soils. They cause excessive growth in the form of nodules on the cortex of the roots of legumes. Cortex is an outer layer of tissue in the roots of dicotyledonous plants located between the stele and epidermis. Biological Science Applications in Agriculture Lesson A4 3 Page 11

12 a. Rhizobia are autotrophic bacteria. Autotrophs are organisms that create their own food rather than obtaining it from other organisms. They get their energy from the oxidation of mineral constituents, as well as carbohydrates from their host plant. b. The rhizobia and the plant live in a symbiotic relationship. Symbiosis is where two dissimilar organisms live together in a mutually beneficial relationship. 7. The soil bacteria enter the plant through openings in the root hairs and extend into the cortex (outer cells) of the rootlets. This causes the growth of nodules to occur and is where nitrogen fixation occurs. 8. The rhizobia fix atmospheric nitrogen (N 2 ) by converting it to ammonia (NH 4+ ). a. Fixed is when a compound resists decomposition. b. Ammonia is then converted to nitrite (NO 2- ) and then to nitrate (NO 3- ). This process is known as nitrification. c. Nitrite is toxic to higher plants, but the conversion from nitrite to nitrate occurs so quickly that no nitrite buildup in the soil or plant roots occurs. 9. It appears that nitrogen, in the form of nitrate, is then diffused through the walls of the bacteria located in the root nodules and is absorbed by the host plant through the nodule root system. F. To complete the nitrogen cycle, nitrogen can be removed from the soil by the uptake of nitrogen by the plant, losses due to leaching, or by denitrification. 1. Denitrification is when nitrates are converted to nitrogen gas. 2. Denitrification occurs in soils that have no oxygen because of saturation from water; the nitrogen is then lost to the atmosphere. G. Seeds are inoculated with rhizobia in order to increase the bacterial populations in the soils of leguminous plants. Inoculation is the bulk treatment of leguminous seeds with rhizobia. 1. Increased rhizobia populations will fix more nitrogen, making more nitrogen available to the plant. 2. The increased supply of nitrogen by rhizobia lessens the need for supplemental nitrogen and generally increases the yield and quality of crops. 3. However, these bacteria are crop-specific, with certain strains affecting only certain crops. H. Factors affecting rhizobium activity include: 1. As soil temperature increases, soil bacteria become more active. This explains why nodules are not present in legumes during the winter months. Research has also shown that nodules slough off immediately after crop harvest, and then begin to return several days after harvest. 2. Their populations are increased by soil moisture, soil oxygen, and soil aeration. 3. A ph of supports the greatest rhizobia populations. 4. Also, the greater the exchangeable calcium in the soil, the greater the soil bacteria populations. Biological Science Applications in Agriculture Lesson A4 3 Page 12

13 I. Nitrogen can also be added to the soil by lightning, application of commercial fertilizers, and through decomposition of dead organisms. Use TM J through TM L to reinforce the general concept of the nitrogen cycle. Have students sketch the nitrogen cycle. Discuss the sketches and use student comments as a basis for determining if any portion of the content needs to be taught again. Contact your local fertilizer and chemical company. Have them visit with the class to talk about the industry, crop scouting, how soil tests are taken, how GIS and GPS is used, how management decisions are made, and different types of application methods. Make sure to ask about education and employment experience necessary for the different types of jobs. Tie the different aspects of nutrient management to science and emphasize how new technologies are making increased yields and disease protection possible. Visit Monsanto s Research Center in Chesterfield, Missouri for a first hand look at research; this must be arranged locally (i.e fertilizer company). Review/Summary. Focus the review and summary of the lesson around the student learning objectives. Call on students to explain the content of each objective. Application. Application can involve one of the following student activities using the attached transparency masters and lab sheets: TM A: Plant Nutrients TM B: Essential Nutrients TM C: Crop Plants with Nutritional Diseases TM D: Examples of Nutrient Deficiencies TM E: Nutrient Supplies TM F: ph Scale TM G: Relationship of ph to Availability of Plant Nutrients in the Soil TM H: Fertilizer Guaranteed Analysis TM I: Nitrogen Cycle TM J: Nitrogen Increases Uptake of Other Nutrients by the Plant TM K: Phosphorus Cycle LS A: Plant Tissue Testing LS B: N, P, & K Functions and Deficiency Symptoms LS C: Plant Nutrient Requirements TS A: Plant Tissue Testing Evaluation. Evaluation should concentrate on student achievement of the lesson s objectives. A sample test is included. Biological Science Applications in Agriculture Lesson A4 3 Page 13

14 Answers to Sample Test: Part One: Matching 1. i 2. g 3. b 4. h 5. c 6. a 7. e 8. d 9. j 10. f 11. k 12. l Part Two: Fill-in-the-Blank 1. nitrogen, phosphorus, potassium 2. calcium, sulfur, magnesium 3. carbon, hydrogen, oxygen Part Three: Multiple Choice 1. a 2. c 3. b 4. d (chlorine) Part Four: Short Answer 1. Plants have different needs at different stages of development. Plants will need a lot of nutrients especially nitrogen as they start to grow at a high rate after germination. When plants start to produce seed and fruit, they require a lot of phosphorus. When the plant reaches maturity or is dormant, its nutrient requirements slow. 2. The plant tissue test is able to use sap from the plant because the nutrients are moved throughout the plant in a water solution. The sap is the water solution containing the nutrients. 3. Nitrogen is a constituent of amino acids (and thus, proteins and enzymes); constituent of chlorophyll (four N atoms in each molecule); stimulates carbohydrate utilization; stimulates root growth and development; and regulates uptake and utilization of other nutrients. Phosphorus is important because it is a component of ATP (adenosine triphosphate), which implements energy-using processes in plants; component of DNA and RNA; used in proteins, metabolic transfer processes, photosynthesis, and respiration; affects cell division, root development, maturation, flowering and fruiting, and overall Biological Science Applications in Agriculture Lesson A4 3 Page 14

15 crop quality. Potassium is important because it activates enzymes; regulates opening and closing of stomata; regulates water uptake by root cells; essential for photosynthesis, starch formulation, and translocation of sugars; aids in nitrogen metabolism; and promotes growth of meristem tissue. 4. Factors affecting nutrient availability include ph, depletion by plants, breakdown of past crops into organic matter, and leaching. 5. Answers will vary. Biological Science Applications in Agriculture Lesson A4 3 Page 15

16 Test Name PLANT TISSUE TESTING Part One: Matching Instructions: Match the word with the correct definition. a. atmospheric macronutrients e. incomplete fertilizer i. nitrogen fixation b. complete fertilizer f. legumes j. plant tissue test c. essential g. macronutrients k. soil d. hydroponics h. micronutrients l. translocation the process of turning atmospheric nitrogen into a usable form for plants by bacteria nutrients needed in large quantities a fertilizer that contains N, P, and K nutrients needed in smaller quantities, but they are still essential this term describes nutrients that plants must have in order to survive these nutrients make up about 80 85% of the weight of a plant a fertilizer that lacks any of the three primary elements a method of growing plants in a nutrient solution a test used to measure the amount of nutrients present in the sap of plants plants that use bacteria to obtain nitrogen from the atmosphere the outer portion of the Earth s surface that supports plant growth the movement of organic molecules throughout plant tissues Part Two: Fill-in-the-Blank Instructions: Complete the following statements. 1.,, and are examples of primary macronutrients. Biological Science Applications in Agriculture Lesson A4 3 Page 16

17 2.,, and are considered secondary macronutrients. 3.,, and are atmospheric macronutrients. Part Three: Multiple Choice Instructions: Circle the letter of the correct answer If a plant has yellow leaves, it is most likely deficient in a. nitrogen b. phosphorus c. potassium d. none of the above If a plant has burning in the leaf margins, lodging, and overall decreased quality, it most likely is deficient in a. nitrogen b. phosphorus c. potassium d. none of the above If a plant has stunted growth and purple leaves, it is most likely deficient in a. nitrogen b. phosphorus c. potassium d. none of the above If a plant experiences wilting, yellowing, and the leaves turn bronze, it is most likely deficient in a. nitrogen b. phosphorus c. potassium d. none of the above Part Four: Short Answer Instructions: Answer the following questions. 1. Why do plant nutrient levels vary by stage of growth? 2. Why can sap from plant tissues be used to determine plant nutrient levels? Biological Science Applications in Agriculture Lesson A4 3 Page 17

18 3. What is the purpose of nitrogen, phosphorus, and potassium in plants? 4. What factors affect the nutrient levels contained in plant tissues? Why? 5. Why is it important to study plant nutrition? Biological Science Applications in Agriculture Lesson A4 3 Page 18

19 TM A PLANT NUTRIENTS (Courtesy, Agricultural Research Service, USDA) While a front-end loader works to fill this bunker silo, agricultural engineer Richard Muck takes forage samples that will be analyzed later for nutritive value and moisture content. t Macronutrients are most limiting t Mnemonic C. B. HOPKiNS CaFO Mighty good Closed Monday Morning See You Zen. Biological Science Applications in Agriculture Lesson A4 3 Page 19

20 TM B ESSENTIAL NUTRIENTS Nitrogen (N) Phosphorus (P) Potassium (K) Sulfur (S) Calcium (Ca) Magnesium (Mg) Boron (B) Copper (Cu) Chlorine (Cl) Iron (Fe) Manganese (Mn) Molybdenum (Mo) Zinc (Zn) Biological Science Applications in Agriculture Lesson A4 3 Page 20

21 TM C CROP PLANTS WITH NUTRITIONAL DISEASES Top left corn ear with boron deficiency. Top right wheat with manganese deficiency. Bottom left potato leaf with potassium deficiency. Bottom right soybean with zinc deficiency. (Courtesy, Potash and Phosphate Institute) Biological Science Applications in Agriculture Lesson A4 3 Page 21

22 TM D EXAMPLES OF NUTRIENT DEFICIENCIES Top left potassium deficiency in alfalfa. Top right nitrogen deficiency in corn. Bottom left iron deficiency in a tomato plant. Bottom right magnesium deficiency in a grape plant. (Courtesy, Potash and Phosphate Institute, Norcross, Georgia) Biological Science Applications in Agriculture Lesson A4 3 Page 22

23 TM E NUTRIENT SUPPLIES Soil is the outer portion of the Earth s crust that supports plant growth Soilless medium Hydroponics Minerals dissolved in a water solution Soil Roots Xylem Translocation is the movement of organic molecules throughout plant tissues Biological Science Applications in Agriculture Lesson A4 3 Page 23

24 TM F ph SCALE Alkaline Range ph Values Degree Excessively Alkaline Strongly Alkaline ph Values of Common Liquids Lemon Juice 3.0 Milk 6.0 Distilled Water 7.0 Soap 9.0 Acid Range Alkaline Weakly Alkaline Neutral Weakly Acid Acid Strongly Acid Excessively Acid Best range for most plants Biological Science Applications in Agriculture Lesson A4 3 Page 24

25 TM G RELATIONSHIP OF ph TO AVAILABILITY OF PLANT NUTRIENTS IN THE SOIL Nitrogen Phosphorus Potassium Sulfur Calcium Magnesium Iron Manganese Boron Copper and Zinc Molybdenum Strongly acid Strongly alkaline Biological Science Applications in Agriculture Lesson A4 3 Page 25

26 TM H FERTILIZER GUARANTEED ANALYSIS 16% nitrogen (N) If it is a 100 pound bag, it contains 16 pounds of nitrogen. FERTILIZER 4% phosphoric acid (aspo) Ifitisa pound bag, it contains 4 pounds of phosphoric acid % potash (as K2O) If it is a 100 pound bag, it contains 8 pounds of potash. Guarenteed percentages by weight This bag has 16% nitrogen, 4% phosphorus, and 8% potassium Balance of weight is filler May be formulated to include herbicides or insecticides Biological Science Applications in Agriculture Lesson A4 3 Page 26

27 TM I THE NITROGEN CYCLE Atmospheric nitrogen Biological fixation Atmospheric fixation Dissolved in waterways Denitrification Nitrate in soil Plant and animal wastes Decomposers Ammonia Runoff and leaching Plant and animal wastes Biological Science Applications in Agriculture Lesson A4 3 Page 27

28 TM J NITROGEN INCREASES UPTAKE OF OTHER NUTRIENTS BY THE PLANT N, % P, % N Rate None 160 lb/a Differences in Content of Other Nutrients K, % Ca, % Mg, % Mn, ppm Fe, ppm Zn, ppm B, ppm Cu, ppm Yield/Acre 118 bu 139 bu Ear-Leaf Sample WHY? Because N becomes building blocks called amino acids inside the plant. Because these building blocks produce protoplasm leading to strong plant cells. Because these cells create a vigorous plant with a root system that searches for other nutrients to help it meet the big-yield appetite N gives it. Biological Science Applications in Agriculture Lesson A4 3 Page 28

29 TM K PHOSPHORUS CYCLE Fertilizer Waste P o P i Runoff Waste Waste Food Fish P i P i P i P o P p Fertilizer phosphate rock, guano P o Available p Mining P i Phytoplankton P o Zooplankton P i P i P i P - phosphorus p - particulate o - organic i - inorganic Bacteria Zooplankton P o Biological Science Applications in Agriculture Lesson A4 3 Page 29

30 LS A: Teacher Information PLANT TISSUE TESTING Research Problem How can the nutrient levels contained in plant tissues be estimated? Agricultural Applications and Practices Maintaining the nutrient levels of crops is a critical element in plant growth and management. Traditionally, soil nutrient levels have been interpreted as an estimate of actual nutrient uptake by plants. However, scientists know that there is a difference between total soil nutrient levels and nutrients in the soil that are actually available for uptake by plants. Two methods for determining the amounts of essential nutrients contained in plant tissues have been developed in recent years. Plant tissue analysis is a laboratory procedure now conducted by many soil testing labs which gives an accurate indication of plant nutrition levels. Sophisticated equipment is needed for conducting this analysis, and soil testing labs charge a small fee for the test. Plant tissue testing is another procedure which has been developed for estimating plant nutrition levels. Unlike plant tissue analysis, plant tissue testing can be done in the field or greenhouse using a simple kit which contains nutrient extractants. An extractant is a solvent used in extracting or separating out the nutrient elements of a compound or substance Plant tissue testing can be done to monitor plant nutrient levels during the growing season. While the test is a general estimate of plant nutrient levels, it can be used to diagnose nutrient deficiency problems. Plant tissue testing is used in combination with soil tests to strengthen the reliability of the test results. Fertilizers are one of the most critical and expensive inputs into any crop production enterprise. Thus, growers use soil and tissue tests to make certain that their fertility program is sound and cost effective. Science Connections Questions for Investigation 1. How do plant nutrient levels vary by stage of growth? Why? 2. Why can sap from plant tissues be used to determine plant nutrient levels? 3. Why are nitrogen, phosphorus, and potassium needed by plants? 4. Why does additional nitrogen enhance the green color of leaves? 5. What factors affect the nutrient levels contained in plant tissues? Why? Biological Science Applications in Agriculture Lesson A4 3 Page 30

31 Purpose of Lab and Student Performance Objectives The purpose of this laboratory is to determine the nutrient levels contained in succulent parts of a plant, using a tissue testing kit. Students will be able to: 1. Conduct a tissue test on a variety of growing plants. 2. Interpret the results of a plant tissue test. 3. Compare the results of tissue tests and soil tests and develop appropriate recommendations. 4. Explain why plant nutrient levels may vary from soil nutrient levels and by stage of plant growth. Materials and/or Equipment leaf and stem samples from plants to be tested (use representative plants in large growing conditions) plant tissue testing kit paper towels Helpful Hints Plant tissue testing kits can be purchased from science supply companies such as NASCO or Carolina Biological. In addition, students can perform a soil test on the soil that their plants are growing in and compare the results. To be most effective, this lesson should be taught after students have studied soil fertility and tested soils, using kits and commercial tests. Anticipated Findings Results of tissue tests depend upon weather conditions, the plant part from which sap is drawn, and other factors. Actual test results will vary according to the general nutrient levels of the test plants. Run tests on more than one part of the same plant to check the consistency of results and interpretations. Combine test results for multiple tests on single plants and determine an average level of major nutrients for each plant. Have students record their test results on poster board or the chalkboard for comparison and summary. Biological Science Applications in Agriculture Lesson A4 3 Page 31

32 Ideas for Additional Experiments 1. Compare test results from various parts of the same plant. 2. Compare results under differing soil conditions. 3. Compare tissue test results with soil test results. 4. Compare results from the same crop at various stages in the growing season. 5. Compare results after the addition of fertilizers and soil amendments. Check nutrient levels at 10 day intervals following applications. 6. Use a hydroponics unit to create specific nutrient deficiencies in plants and verify with plant tissue testing. Procedure Give each student or group of students a copy of the worksheet to perform the activity. Biological Science Applications in Agriculture Lesson A4 3 Page 32

33 LS A: Student Worksheet Name PLANT TISSUE TESTING Procedure 1. Collect plant tissue samples according to directions contained in the tissue testing kit. 2. Conduct nutrient tests for N, P, and K. Carefully follow directions in the kit. 3. Record results for each test in a well organized table make sure to include the name of the plant and the part of the plant that was tested. 4. Use the interpretation guide, along with soil test results, to determine if adjustments are needed in fertility and/or ph. Data Summary Table for Plant Tissue Testing Species/plant number or source Results of tissue test Results of soil test N P K N P K Biological Science Applications in Agriculture Lesson A4 3 Page 33

34 LS B: Information Sheet Name N, P, & K FUNCTIONS AND DEFICIENCY SYMPTOMS N P K Functions Constituent of amino acids (and thus, proteins and enzymes) Constituent of chlorophyll (four N atoms in each molecule) Stimulates carbohydrate utilization Stimulates root growth and development Regulates uptake and utilization of other nutrients Component of ATP (adenosine triphosphate), which implements energyusing processes in plants Component of DNA and RNA Used in proteins, metabolic transfer processes, photosynthesis, and respiration Affects cell division, root development, maturation, flowering and fruiting, and overall crop quality Activates enzymes Regulates opening and closing of stomata Regulates water uptake by root cells Essential for photosynthesis, starch formulation, and translocation of sugars Aids in nitrogen metabolism Promotes growth of meristem tissue Deficiency Symptoms Stunted and slow growth Yellowing of lower leaves of plant Poor root system Purpling of the stem, leaf, or veins on the underside of leaves Stunted growth and maturity Reduced yields due to decreased seed and fruit formation Burn or scorch of margins of leaves, particularly older leaves Lodging Decreased yields Lack of disease resistance Decreased crop quality Poor root system Biological Science Applications in Agriculture Lesson A4 3 Page 34

35 LS C: Information Sheet Name PLANT NUTRIENT REQUIREMENTS Nutrient Element Forms Absorbed Function in Plants Deficiency Symptoms Nitrogen (N) NO 3- or NH + 4 Constituent of amino acids (and thus, proteins and enzymes); constituent of chlorophyll (four N atoms in each molecule); stimulates carbohydrate utilization; stimulates root growth and development; regulates uptake and utilization of other nutrients Stunted and slow growth; yellowing of lower leaves of plant; poor root system Phosphorus (P) H 2 PO 4- or HPO 2-4 Component of ATP (adenosine triphosphate), which implements energy-using processes in plants; component of DNA and RNA; used in proteins, metabolic transfer processes, photosynthesis, and respiration; affects cell division, root development, maturation, flowering and fruiting, and overall crop quality Purpling of the stem, leaf, or veins on the underside of leaves; stunted growth and maturity; reduced yields due to decreased seed and fruit formation; poor root system Potassium (K) K + Activates enzymes; regulates opening and closing of stomata; regulates water uptake by root cells; essential for photosynthesis, starch formulation, and translocation of sugars; aids in nitrogen metabolism; promotes growth of meristem tissue Burn or scorch of margins of leaves, particularly older leaves; lodging; decreased yields; lack of disease resistance; decreased crop quality Biological Science Applications in Agriculture Lesson A4 3 Page 35

36 Nutrient Element Forms Absorbed Function in Plants Deficiency Symptoms Sulfur (S) SO 2-4 Essential component of amino acids and vitamins Calcium (Ca) Ca 2+ Component of cell walls, needed for cell growth and division Magnesium (Mg) Mg 2+ Needed in chlorophyll, used in vitamins and amino acids, used in fat and sugar formation, needed for seed germination Boron (B) BO 3- or B 4 O 2-7 Affects pollen germination, cell division, metabolism of nitrogen, fruiting, water regulation, and hormone movement Copper (Cu) Cu 2+ Part of enzymes, used in chlorophyll synthesis, catalyst in respiration, protein, and carbohydrate metabolism Yellowing of leaves, light green leaves, slow growth; looks similar to nitrogen deficiency symptoms Terminal leaves may be deformed, stunted root growth, dead spots in midribs, black color to plant Yellowing between veins and leaves may droop Death of terminal buds, thickening of leaves, leaves curl and die, lateral buds grow and then die Death of terminal leaf buds, yellowing between veins, slowed growth Chlorine (Cl) Cl - Helps in shoot and root growth Wilting of plants, yellowing, leaves turn bronze Iron (Fe) Fe 2+,Fe 3+ Found in enzymes, helps to form a variety of compounds, catalyst in chlorophyll synthesis Manganese (Mn) Mn 2+ Helps synthesize chlorophyll, serves as a coenzyme Molybdenum (Mo) MoO 2-4 Used in protein synthesis, needed for some enzymes Zinc (Zn) Zn 2+ Forms chloroplasts, auxins, and starch, needed by legumes for seed development Yellowing or light green in leaves, yellowing between veins Light green between green veins, leaves then turn white Causes nitrogen deficiency and thus similar signs Roots are abnormal, yellowing between veins, leaves become bronzed or mottled Biological Science Applications in Agriculture Lesson A4 3 Page 36

37 TS A Technical Supplement PLANT TISSUE TESTING 1. How do plant nutrient levels vary by stage of growth? Why? The plant nutrients vary to accommodate the different stages of growth. For example, during cell division and protein synthesis, the plant needs higher amounts of phosphorus and nitrogen. DNA has a phosphate backbone and nitrogen is also needed in the formation of DNA. Phosphorus is also needed in ATP formation. ATP is needed for photosynthesis and other chemical reactions. Potassium is needed for water retention and stomata functions. The demand for nutrients will depend upon the stage of growth such as seedling, vegetative, or reproductive. 2. Why can sap from plant tissues be used to determine plant nutrient levels? The sap transfers the nutrients throughout the plant reflecting the gradient levels and relative constitution in the plant. (This is much like how blood flows through the human body.) 3. Why are nitrogen, phosphorus, and potassium needed by plants? These three nutrients are absolute requirements for plants. The plant can synthesize sugars and fix carbon dioxide, but needs fixed nitrogen, potassium, and phosphorus in absorbable forms. Nitrogen is involved in the photosynthesis process because it is a component of chlorophyll. A deficiency of phosphorus results in stunted growth by preventing cell division. Potassium s function is not completely known, however, it is an activator of many enzymes that are involved in the maintenance of the correct electrical potential of the plasmalemma (film membrane that surrounds the cell). Biological Science Applications in Agriculture Lesson A4 3 Page 37