PLANT TISSUE TESTING -...

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 nutri-ent 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 reactionsby which lime and sulfur impact soil pH.

Student Learning Objectives. Instruction in this lesson should result in stu-dents 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 •

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 Sci-ence—Problem Area 4. Environmental Factors Affecting Plant Growth—Les-son 5. Determining Plant Nutrients and Fertility. Danville, IL: CAERT, Inc.

Animal, Plant, and Soil Science Lesson Plan Library—Unit C. Plant and Soil Sci-ence—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 Proper-ties of Growing Media. Danville, IL: CAERT, Inc.

Osborne, Edward W. Biological Science Applications in Agriculture. Danville, IL: Inter-state Publishers, Inc., 1994.

Towle, Albert. Modern Biology. Austin: Holt, Rinehart and Winston, 2003.

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


� 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 thelesson. Teachers often develop approaches for their unique class and student situations. A possi-ble 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 addi-

tion 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 metabolicprocesses of life. Plants require water, carbon dioxide, oxygen, and a variety of essentialminerals in order to survive.

A. About 80–85% of the weight of a fresh plant is water. The remaining part of the plantcontains elements that are absorbed through the roots and used for plant growth.


B. Plants receive most of the nutrients that they need from the growing media, or in thecase of hydroponics, the nutrient solution that the roots are exposed to. In order tomaintain healthy plants, a grower must provide the right type and amount of nutrientsto 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, andsecondary 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 acquirecarbon, hydrogen, and oxygen from carbon dioxide (CO2) and water (H2O)through the process of photosynthesis. The rest of the dry weight is made up ofminerals.

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 thetissues of a plant to determine which nutrients are present or deficient (absent or lack-ing). When nutrients are deficient in the soil, the plant growth is adversely affected.Oftentimes, plants visibly show a nutrient deficiency by turning colors. When nitrogenis deficient in the soil, a plant’s older leaves will start to turn yellow (chlorosis) and even-tually die. A plant will show purpling in the stem or leaf when phosphorus is deficient inthe soil. Burning or scorching of the leave’s margins may indicate a potassium defi-ciency.

G. Because macronutrients are needed in larger quantities they are usually the ones that arethe most limiting to plant production and thus are the ones that producers will add totheir crops.

H. Mnemonics (pronounced ni-mon-iks) is the art of improving the memory using a for-mula. 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 mne-

monic to help them remember the macronutrients and/or micronutrients.


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) absenceof the element results in abnormal growth, injury, or death; (b) the plant is unable to com-plete 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.

NutrientElement

FormsAbsorbed Function in Plants Deficiency Symptoms

Nitrogen (N) NO3- or NH4

+ Constituent of amino acids(and thus, proteins andenzymes); constituent ofchlorophyll (four N atoms ineach molecule); stimulatescarbohydrate utilization;stimulates root growth anddevelopment; regulatesuptake and utilization of othernutrients

Stunted and slow growth;yellowing of lower leaves ofplant; poor root system

Phosphorus (P) H2PO4- or HPO4

2- Component of ATP (adenosinetriphosphate), whichimplements energy-usingprocesses in plants;component of DNA and RNA;used in proteins, metabolictransfer processes,photosynthesis, andrespiration; affects celldivision, root development,maturation, flowering andfruiting, and overall cropquality

Purpling of the stem, leaf, orveins on the underside ofleaves; stunted growth andmaturity; reduced yields dueto decreased seed and fruitformation; poor root system

Potassium (K) K+ Activates enzymes; regulatesopening and closing ofstomata; regulates wateruptake by root cells; essentialfor photosynthesis, starchformulation, and translocationof sugars; aids in nitrogenmetabolism; promotes growthof meristem tissue

Burn or scorch of margins ofleaves, particularly olderleaves; lodging; decreasedyields; lack of diseaseresistance; decreased cropquality

Sulfur (S) SO42- Essential component of amino

acids and vitaminsYellowing of leaves, lightgreen leaves, slow growth;looks similar to nitrogendeficiency symptoms


NutrientElement


Calcium (Ca) Ca2+ Component of cell walls,needed for cell growth anddivision

Terminal leaves may bedeformed, stunted rootgrowth, dead spots in midribs,black color to plant

Magnesium (Mg) Mg2+ Needed in chlorophyll, used invitamins and amino acids,used in fat and sugarformation, needed for seedgermination

Yellowing between veins andleaves may droop

Boron (B) BO3- or B4O72- Affects pollen germination,

cell division, metabolism ofnitrogen, fruiting, waterregulation, and hormonemovement

Death of terminal buds,thickening of leaves, leavescurl and die, lateral buds growand then die

Copper (Cu) Cu2+ Part of enzymes, used inchlorophyll synthesis, catalystin respiration, protein, andcarbohydrate metabolism

Death of terminal leaf buds,yellowing between veins,slowed growth

Chlorine (Cl) Cl- Helps in shoot and rootgrowth

Wilting of plants, yellowing,leaves turn bronze

Iron (Fe) Fe2+, Fe3+ Found in enzymes, helps toform a variety of compounds,catalyst in chlorophyllsynthesis

Yellowing or light green inleaves, yellowing betweenveins

Manganese (Mn) Mn2+ Helps synthesize chlorophyll,serves as a coenzyme

Light green between greenveins, leaves then turn white

Molybdenum (Mo) MoO42- Used in protein synthesis,

needed for some enzymesCauses nitrogen deficiencyand thus similar signs

Zinc (Zn) Zn2+ Forms chloroplasts, auxins,and starch, needed bylegumes for seed development

Roots are abnormal, yellowingbetween veins, leaves becomebronzed or mottled

Plant Nutrient Requirements

Name Symbol Ionic form Ionic Name

Macronutrients

Primary

Nitrogen N N03; NH4+ Nitrate, ammonium

Phosphorus P HPO;2, H2P04 Orthophosphates

Potassium K K+ —

Secondary

Calcium Ca Ca+2 —

Magnesium Mg Mg+2 —

Sulfur S SO42 Sulfate


Plant Nutrient Requirements

Name Symbol Ionic form Ionic Name

Micronutrients

Boron B B04-2 Borate

Copper Cu Cu+2 —

Chlorine Cl Cl- Chloride

Iron Fe Fe+2, Fe+3 Ferrous, ferric

Manganese Mn Mn+2 Manganous

Molybdenum Mo MoO4-2 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 nutri-ents?

III. Nutrients are supplied through the growing medium or nutrient solution. Plant analysiscan 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. Thereare 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 plantsneed the minerals and water from the medium. Examples include perilite and vermicu-lite.

C. Hydroponics is a method of growing plants in a nutrient solution. The plants in a hydro-ponics unit could be supported in a sand or gravel substrate for support or the rootscould be left bare. With bare roots, the plants’ root system can float in the nutrient richsolution, or the nutrients could be sprayed directly onto the roots.

D. These essential minerals are dissolved in a water or aqueous solution. This solutionmoves from the soil or surrounding environment through the root into the xylem.Translocation is the movement of organic molecules throughout plant tissues. Most ofthe water and nutrients are absorbed through the root hairs. With the help of adhesiveand cohesive properties of water, the solution moves upward against the force of gravity


to the various parts of the plant usually the leaves. Most of the water is lost through tran-spiration via the stomata. This also aids in the movement of water from the roots to therest 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 sam-

ples 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 aproblem 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 runsfrom 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 plantsgrow best within the pH range of 5.5 to 8.0.

2. The pH value of soil is important to agriculturists because certain nutrients becomeunavailable 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 feedextensively. A crop will develop a root system 6 feet or more in depth in some soils to getwater 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 ofnitrogen, sulfur, and other nutrients. Nutrients are less soluble in cool soils, and thatincreases deficiency potential. Phosphorus and potassium diffuse more slowly in coolsoils. 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, andstems 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 contami-nation has occurred, or where poor quality water has been used for irrigation.


I. Herbicides and mechanical controls are more important today than ever before. Weedsrob crop plants of water, air, light, and nutrients. Some weeds may even release sub-stances that inhibit crop growth.

J. Some soils develop hardpans (compaction) and require deep tillage. This requires morephosphorus and potassium to build up fertility.

K. Row width, spacing of plants in the row, and number of plants per acre have importanteffects on yields.

L. Irrigation water can contain nitrate, sulfate, boron, potassium, bicarbonate, chlorine andother salts. A water analysis should be used to modify production practices for utiliza-tion 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 pres-ent in the soil.

Anticipated Problem: If insufficient levels of nutrients are found in the soil, where do theplants 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, show-ing stunted growth, unhealthy coloring of the leaves, and may be more prone to disease andinsect problems.

A. Nutrients may become depleted by growing crops. Since crops are harvested, theorganic 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 thegrower to continually add the nutrients. The nutrients can sometimes be present in thegrowing medium, but they are not available for the plants to take up into their rootsbecause the pH level in the soil is not conducive to plant growth. Plants have differentpH requirements.

B. As a result, growers must add artificial fertilizers, manure, or other organic matter to thesoil or nutrient solution for the plants to use. Soil or plant tissue tests should be con-ducted before fertilizers are added.

1. A fertilizer is any material that is provided to plants to supply the nutrients neededfor plant growth. Fertilizers vary in the components they contain, the way they areapplied, and the function they serve.

2. When choosing a fertilizer to use, one should always look for the fertilizer analysison 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 as3 numbers, for example, (15-10-26). The numbers, always in this order, representthe percent of nitrogen, phosphorus, and potash, present in the fertilizer. So the


example above has 15% nitrogen, 10% phosphate, and 6% potash. Fillers are madeup of the remaining essential plant nutrients and are used to ensure a more evenapplication of the fertilizer. The amount of filler in the above example can be calcu-lated: 100-(15 + 10 + 16) = 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 afertilizer 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 deter-mining 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 thatoverall 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 greencolor. Although the atmosphere is 78% nitrogen gas, it is the most common nutrient defi-ciency seen in plants. N2 gas contains a triple bond which is extremely hard to break; thismakes the molecule almost inert. Nitrogen fertilizer is expensive to produce and is thus anexpensive input for farmers. Leguminous crops are able to use atmospheric nitrogen ratherthan rely on the application of fertilizer; this is an important factor in planning a sustainableagriculture program.

A. The nitrogen cycle is the recycling of nitrogen as it moves between the abiotic (non-liv-ing) and biotic (living) parts of the environment. The largest proportion of nitrogen atany 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 well-known example of this process. The phosphorus and potassium cycles act in a simi-lar manner.

2. The key concept is that no element is lost or consumed in the environment, butrather it changes form and moves between the abiotic and biotic components of theenvironment and is recycled.

B. Nitrogen is essential to all living organisms because of its use in the synthesis ofenzymes, proteins, and chromosomes. In plants, nitrogen is an important component ofchlorophyll.

C. Plants absorb nitrogen as inorganic nitrate ions (NO3-) and in a few cases as ammonium

(NH4+) or amino (NH2

+) ions.


1. The positive charge of ammonium causes it to easily bond to clay soils making itunavailable.

2. The negative charge of nitrate causes it to easily leached away; this can become acause for water contamination. High nitrite levels in water can cause illness espe-cially in children.

3. Nitrogen that is absorbed by the plant is reduced to N2-, NH- or NH2 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 oforganic nitrogen. These must be oxidized before plants can use them.1. The transformation of organic matter to the inorganic or mineral form (NH4

+,NO2

-, or NO3-) is called mineralization.

2. Immobilization is the conversion of nitrogen from an inorganic or mineral form toan organic form. This process occurs naturally during initial decomposition ornitrogen can be immobilized during chemical fertilizer composition to make itavailable to the plant at a later time.

E. Nitrogen fixation is the conversion of atmospheric nitrogen into oxidized forms that canbe assimilated by plants.1. A symbiotic relationship that exists between bacteria and legume plants is utilized to

convert nitrogen gas (N2) to ammonium ions (NH4+) 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 fam-ily Leguminosae; they have the characteristic capability to fix atmospheric nitrogenin nodules on their roots with the aid of certain bacteria.

4. Aquatic ferns and Gunnera macrophylla (tropical plant) form symbiotic relationshipswith blue-green algae to attain their nitrogen. Acacias, mesquites, alder, buckthorn,Casuarina, and paloverde plants also rely on bacteria. Lichens form a relationshipwith cyanobacteria which enables them to be one of the first organisms seen in pri-mary 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 bacteriaare free living nitrogen fixing organisms. Those that form symbiotic relationshipswith 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 anouter layer of tissue in the roots of dicotyledonous plants located between the steleand epidermis.


a. Rhizobia are autotrophic bacteria. Autotrophs are organisms that create theirown food rather than obtaining it from other organisms. They get their energyfrom the oxidation of mineral constituents, as well as carbohydrates from theirhost plant.

b. The rhizobia and the plant live in a symbiotic relationship. Symbiosis is wheretwo dissimilar organisms live together in a mutually beneficial relationship.

7. The soil bacteria enter the plant through openings in the root hairs and extend intothe cortex (outer cells) of the rootlets. This causes the growth of nodules to occurand is where nitrogen fixation occurs.

8. The rhizobia “fix” atmospheric nitrogen (N2) by converting it to ammonia (NH4+).

a. Fixed is when a compound resists decomposition.b. Ammonia is then converted to nitrite (NO2

-) and then to nitrate (NO3-). 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 thenodule root system.

F. To complete the nitrogen cycle, nitrogen can be removed from the soil by the uptake ofnitrogen 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 withrhizobia.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 whynodules are not present in legumes during the winter months. Research has alsoshown that nodules slough off immediately after crop harvest, and then begin toreturn several days after harvest.

2. Their populations are increased by soil moisture, soil oxygen, and soil aeration.3. A pH of 6.0–8.0 supports the greatest rhizobia populations.4. Also, the greater the exchangeable calcium in the soil, the greater the soil bacteria

populations.


I. Nitrogen can also be added to the soil by lightning, application of commercial fertiliz-ers, 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 dis-

ease 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 com-

pany).

Review/Summary. Focus the review and summary of the lesson around the studentlearning objectives. Call on students to explain the content of each objective.

Application. Application can involve one of the following student activities using theattached 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’sobjectives. A sample test is included.


Answers to Sample Test:

Part One: Matching

1. i2. g3. b4. h5. c6. a7. e8. d9. j

10. f11. k12. l

Part Two: Fill-in-the-Blank

1. nitrogen, phosphorus, potassium2. calcium, sulfur, magnesium3. carbon, hydrogen, oxygen

Part Three: Multiple Choice

1. a2. c3. b4. d (chlorine)

Part Four: Short Answer

1. Plants have different needs at different stages of development. Plants will need a lot ofnutrients especially nitrogen as they start to grow at a high rate after germination. Whenplants start to produce seed and fruit, they require a lot of phosphorus. When the plantreaches 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 movedthroughout the plant in a water solution. The sap is the water solution containing thenutrients.

3. Nitrogen is a constituent of amino acids (and thus, proteins and enzymes); constituent ofchlorophyll (four N atoms in each molecule); stimulates carbohydrate utilization; stimu-lates root growth and development; and regulates uptake and utilization of other nutri-ents. Phosphorus is important because it is a component of ATP (adenosinetriphosphate), which implements energy-using processes in plants; component of DNAand RNA; used in proteins, metabolic transfer processes, photosynthesis, and respiration;affects cell division, root development, maturation, flowering and fruiting, and overall


crop quality. Potassium is important because it activates enzymes; regulates opening andclosing of stomata; regulates water uptake by root cells; essential for photosynthesis,starch formulation, and translocation of sugars; aids in nitrogen metabolism; and pro-motes growth of meristem tissue.

4. Factors affecting nutrient availability include pH, depletion by plants, breakdown of pastcrops into organic matter, and leaching.

5. Answers will vary.


Name ________________________________________Test


� Part One: Matching

Instructions: Match the word with the correct definition.

a. atmospheric macronutrients e. incomplete fertilizer i. nitrogen fixationb. complete fertilizer f. legumes j. plant tissue testc. essential g. macronutrients k. soild. hydroponics h. micronutrients l. translocation

_______1. the process of turning atmospheric nitrogen into a usable form for plants by bacteria

_______2. nutrients needed in large quantities

_______3. a fertilizer that contains N, P, and K

_______4. nutrients needed in smaller quantities, but they are still essential

_______5. this term describes nutrients that plants must have in order to survive

_______6. these nutrients make up about 80–85% of the weight of a plant

_______7. a fertilizer that lacks any of the three primary elements

_______8. a method of growing plants in a nutrient solution

_______9. a test used to measure the amount of nutrients present in the sap of plants

______10. plants that use bacteria to obtain nitrogen from the atmosphere

______11. the outer portion of the Earth’s surface that supports plant growth

______12. the movement of organic molecules throughout plant tissues

� Part Two: Fill-in-the-Blank

Instructions: Complete the following statements.

1. __________________, ___________________, and ___________________ are examples of primarymacronutrients.


2. ___________________, ___________________, and __________________ are considered secondarymacronutrients.

3. __________________, _____________________, and ___________________ are atmospheric macronutrients.

� Part Three: Multiple Choice

Instructions: Circle the letter of the correct answer.

_______1. If a plant has yellow leaves, it is most likely deficient in

a. nitrogenb. phosphorusc. potassiumd. none of the above

_______2. If a plant has burning in the leaf margins, lodging, and overall decreased quality, it most likely is defi-cient in


_______3. If a plant has stunted growth and purple leaves, it is most likely deficient in


_______4. If a plant experiences wilting, yellowing, and the leaves turn bronze, it is most likely deficient in


� 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?


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?


TM–A

PLANT NUTRIENTS

While a front-end loader works to fill this bunker

silo, agricultural engineer Richard Muck takes for-

age samples that will be analyzed later for nutritive

value and moisture content.

�Macronutrients are most limiting

�Mnemonic

� C. B. HOPKiNS CaF� Mighty good Closed

Monday Morning See You Zen.


(Courtesy, Agricultural Research Service, USDA)

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)


TM–C

CROP PLANTS WITHNUTRITIONAL 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)


TM–D

EXAMPLES OFNUTRIENT 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)


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


TM–F

pH SCALE


pH Values

pH Values of Common LiquidsLemon Juice 3.0

Milk 6.0Distilled Water 7.0

Soap 9.0

Degree

8

9

10

11

12

13

14

7

6

5

4

3

2

1

0

NeutralBest range

for mostplants

WeaklyAcid

WeaklyAlkaline

Acid

Alkaline

StronglyAcid

StronglyAlkaline

ExcessivelyAcid

ExcessivelyAlkaline

Alk

alin

eR

an

ge

Acid

Ran

ge

TM–G

RELATIONSHIP OF pH TOAVAILABILITY OF

PLANT NUTRIENTS IN THE SOIL


4.0

Strongly acid Strongly alkaline

5.0 6.0 7.0 8.0 9.0 10.0

Nitrogen

Phosphorus

Sulfur

Calcium

Magnesium

Potassium

Iron

Manganese

Boron

Copper and Zinc

Molybdenum

TM–H

FERTILIZER GUARANTEED ANALYSIS


16 4 8

FERTILIZER16% nitrogen (N)—

If it is a 100 poundbag, it contains 16pounds of nitrogen.

4% phosphoric acid(as P O )—If it is a100 pound bag, itcontains 4 poundsof phosphoric acid.

2 5

8% potash (as K O)—

If it is a 100 poundbag, it contains 8pounds of potash.

2

• 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

TM–I

THE NITROGEN CYCLE


Atmospheric nitrogen

Biological fixation

Denitrification

Atmosphericfixation

Nitrate insoil

Ammonia

Decomposers

Plant andanimal wastes

Runoff andleaching

Dissolvedin waterways

Plant andanimalwastes

TM–J

NITROGEN INCREASES UPTAKE OFOTHER NUTRIENTS BY THE PLANT


N, %

P, %

K, %

Ca, %

Mg, %

Mn, ppm

Fe, ppm

Zn, ppm

B, ppm

Cu, ppm

Yield/Acre 118 bu 139 bu

2.36

0.18

2.22

0.66

0.24

40

163

22

12

10

3.02

0.26

2.44

0.68

0.26

47

162

36

18

14

+0.08

+0.22

+0.02

+0.02

+7

–1

+14

+6

+4

Differences inContent of

Other Nutrients

Ear-LeafSample

None 160 lb/A

N Rate

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.

TM–K

PHOSPHORUS CYCLE


Po

Po

Pi

Pi

Pi

Pi

PiPiPi

Po Pi

Pp

Po

Po

ZooplanktonPhytoplankton

Zooplankton

Bacteria

Fertilizer

Waste Waste

Waste

Runoff

Food

Fish

Fertilizerphosphaterock, guano

Available pMining

Ppoi

- phosphorus- particulate- organic- inorganic

LS–A: Teacher Information


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 manage-ment. Traditionally, soil nutrient levels have been interpreted as an estimate of actualnutrient uptake by plants. However, scientists know that there is a difference betweentotal soil nutrient levels and nutrients in the soil that are actually available for uptake byplants.

Two methods for determining the amounts of essential nutrients contained in plant tis-sues have been developed in recent years. Plant tissue analysis is a laboratory procedurenow conducted by many soil testing labs which gives an accurate indication of plant nutri-tion levels. Sophisticated equipment is needed for conducting this analysis, and soil test-ing labs charge a small fee for the test. Plant tissue testing is another procedure which hasbeen developed for estimating plant nutrition levels. Unlike plant tissue analysis, planttissue testing can be done in the field or greenhouse using a simple kit which containsnutrient extractants. An extractant is a solvent used in extracting or separating out thenutrient elements of a compound or substance

Plant tissue testing can be done to monitor plant nutrient levels during the growing sea-son. While the test is a general estimate of plant nutrient levels, it can be used to diagnosenutrient deficiency problems. Plant tissue testing is used in combination with soil tests tostrengthen the reliability of the test results. Fertilizers are one of the most critical andexpensive inputs into any crop production enterprise. Thus, growers use soil and tissuetests 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?


3. Why are nitrogen, phosphorus, and potassium needed by plants?

4. Why does additional nitrogen enhance the green color of leaves?



Purpose of Lab and Student Performance Objectives

The purpose of this laboratory is to determine the nutrient levels contained in succulentparts 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 recom-mendations.

4. Explain why plant nutrient levels may vary from soil nutrient levels and by stage ofplant growth.

Materials and/or Equipment

� leaf and stem samples from plants to be tested (use representative plants in large grow-ing conditions)

� plant tissue testing kit

� paper towels

Helpful Hints

� Plant tissue testing kits can be purchased from science supply companies such asNASCO or Carolina Biological.

� In addition, students can perform a soil test on the soil that their plants are growing inand compare the results.

� To be most effective, this lesson should be taught after students have studied soil fertil-ity and tested soils, using kits and commercial tests.

Anticipated Findings

Results of tissue tests depend upon weather conditions, the plant part from which sap isdrawn, and other factors. Actual test results will vary according to the general nutrient lev-els of the test plants. Run tests on more than one part of the same plant to check the con-sistency of results and interpretations. Combine test results for multiple tests on singleplants and determine an average level of major nutrients for each plant. Have studentsrecord their test results on poster board or the chalkboard for comparison and summary.


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 nutri-ent levels at 10 day intervals following applications.

6. Use a hydroponics unit to create specific nutrient deficiencies in plants and verifywith plant tissue testing.

Procedure

Give each student or group of students a copy of the worksheet to perform the activity.


Name ________________________________________LS–A: Student Worksheet


Procedure

1. Collect plant tissue samples according to directions contained in the tissue testingkit.

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 thename 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 adjustmentsare needed in fertility and/or pH.

Data Summary Table for Plant Tissue Testing

Species/plantnumber or source

Results of tissue test Results of soil test

N P K N P K


Name ________________________________________LS–B: Information Sheet

N, P, & K—FUNCTIONS ANDDEFICIENCY SYMPTOMS

N P K

Functions • Constituent of amino acids(and thus, proteins andenzymes)

• Constituent of chlorophyll(four N atoms in eachmolecule)

• Stimulates carbohydrateutilization

• Stimulates root growth anddevelopment

• Regulates uptake andutilization of other nutrients

• Component of ATP(adenosine triphosphate),which implements energy-using processes in plants

• Component of DNA andRNA

• Used in proteins, metabolictransfer processes,photosynthesis, andrespiration

• Affects cell division, rootdevelopment, maturation,flowering and fruiting, andoverall crop quality

• Activates enzymes

• Regulates opening andclosing of stomata

• Regulates water uptake byroot cells

• Essential for photosynthesis,starch formulation, andtranslocation of sugars

• Aids in nitrogen metabolism

• Promotes growth ofmeristem tissue

DeficiencySymptoms

• Stunted and slow growth

• Yellowing of lower leaves ofplant

• Poor root system

• Purpling of the stem, leaf, orveins on the underside ofleaves

• Stunted growth andmaturity

• Reduced yields due todecreased seed and fruitformation

• Poor root system

• Burn or scorch of margins ofleaves, particularly olderleaves

• Lodging

• Decreased yields

• Lack of disease resistance

• Decreased crop quality


Name ________________________________________LS–C: Information Sheet

PLANT NUTRIENT REQUIREMENTS

NutrientElement


Nitrogen (N) NO3- or NH4

+ Constituent of amino acids (andthus, proteins and enzymes);constituent of chlorophyll (four Natoms in each molecule);stimulates carbohydrateutilization; stimulates root growthand development; regulatesuptake and utilization of othernutrients

Stunted and slow growth;yellowing of lower leaves of plant;poor root system

Phosphorus (P) H2PO4- or HPO4

2- Component of ATP (adenosinetriphosphate), which implementsenergy-using processes in plants;component of DNA and RNA; usedin proteins, metabolic transferprocesses, photosynthesis, andrespiration; affects cell division,root development, maturation,flowering and fruiting, and overallcrop quality

Purpling of the stem, leaf, or veinson the underside of leaves;stunted growth and maturity;reduced yields due to decreasedseed and fruit formation; poorroot system

Potassium (K) K+ Activates enzymes; regulatesopening and closing of stomata;regulates water uptake by rootcells; essential for photosynthesis,starch formulation, andtranslocation of sugars; aids innitrogen metabolism; promotesgrowth of meristem tissue

Burn or scorch of margins ofleaves, particularly older leaves;lodging; decreased yields; lack ofdisease resistance; decreased cropquality


NutrientElement


Sulfur (S) SO42- Essential component of amino

acids and vitaminsYellowing of leaves, light greenleaves, slow growth; looks similarto nitrogen deficiency symptoms

Calcium (Ca) Ca2+ Component of cell walls, neededfor cell growth and division

Terminal leaves may be deformed,stunted root growth, dead spotsin midribs, black color to plant

Magnesium (Mg) Mg2+ Needed in chlorophyll, used invitamins and amino acids, used infat and sugar formation, neededfor seed germination

Yellowing between veins andleaves may droop

Boron (B) BO3- or B4O72- Affects pollen germination, cell

division, metabolism of nitrogen,fruiting, water regulation, andhormone movement

Death of terminal buds, thickeningof leaves, leaves curl and die,lateral buds grow and then die

Copper (Cu) Cu2+ Part of enzymes, used inchlorophyll synthesis, catalyst inrespiration, protein, andcarbohydrate metabolism

Death of terminal leaf buds,yellowing between veins, slowedgrowth

Chlorine (Cl) Cl- Helps in shoot and root growth Wilting of plants, yellowing, leavesturn bronze

Iron (Fe) Fe2+, Fe3+ Found in enzymes, helps to form avariety of compounds, catalyst inchlorophyll synthesis

Yellowing or light green in leaves,yellowing between veins

Manganese (Mn) Mn2+ Helps synthesize chlorophyll,serves as a coenzyme

Light green between green veins,leaves then turn white

Molybdenum (Mo) MoO42- Used in protein synthesis, needed

for some enzymesCauses nitrogen deficiency andthus similar signs

Zinc (Zn) Zn2+ Forms chloroplasts, auxins, andstarch, needed by legumes forseed development

Roots are abnormal, yellowingbetween veins, leaves becomebronzed or mottled


TS–A

Technical Supplement


1. How do plant nutrient levels vary by stage of growth? Why?

The plant nutrients vary to accommodate the different stages of growth. For exam-ple, during cell division and protein synthesis, the plant needs higher amounts ofphosphorus and nitrogen. DNA has a phosphate backbone and nitrogen is alsoneeded in the formation of DNA. Phosphorus is also needed in ATP formation.ATP is needed for photosynthesis and other chemical reactions. Potassium isneeded for water retention and stomata functions. The demand for nutrients willdepend upon the stage of growth such as seedling, vegetative, or reproductive.


The sap transfers the nutrients throughout the plant reflecting the gradient levelsand relative constitution in the plant. (This is much like how blood flows throughthe human body.)

3. Why are nitrogen, phosphorus, and potassium needed by plants?

These three nutrients are absolute requirements for plants. The plant can synthesizesugars and fix carbon dioxide, but needs fixed nitrogen, potassium, and phosphorusin absorbable forms. Nitrogen is involved in the photosynthesis process because it isa component of chlorophyll. A deficiency of phosphorus results in stunted growthby preventing cell division. Potassium’s function is not completely known, how-ever, it is an activator of many enzymes that are involved in the maintenance of thecorrect electrical potential of the plasmalemma (film membrane that surrounds thecell).


4. Why does additional nitrogen enhance the green color of leaves?

Nitrogen aids in the plant’s production of chlorophyll. Adding extra nitrogenincreases the lushness of the plant. This is desirable for a crop like alfalfa, lettuce, orspinach where the leaves are the primary plant component being harvested. Addingnitrogen will also enhance the size and attractiveness of carrots, beets, sweet corn,peppers, eggplants, and celery; it does not improve their nutritive quality or flavor.Sometimes nitrogen can diminish the productivity of some crops by slowing thefruiting process. Excessive nitrogen for small grains increases the susceptibility forlodging, thus reducing photosynthetic efficiency and yield.


Factors that would affect nutrient levels are drought, changes in pH, salinity, tem-perature shock, and flooding. Under stress conditions, nutrients become chelated inthe soil and are unavailable to the plant. For example, with flooding, nitrogenbecomes a limiting factor. Bacteria in the soil consume the nitrogen instead of mak-ing it available to the plant. With low pH, phosphorus becomes insoluble in water;and potassium can become mobile, soluble, and easily leached.


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