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Chemical Control of Plant Growth.Agricultural Research Center (DOA), Beltsville,Md.Dec 7223p.; Science Study Aid No. 7Superintendent of Documents, Government PrintingOffice, Washington, D.C. 20402 (Stock No. 0100-02707,$0.30)

MF-$0.65 BC-$3.29Biochemistry; *Chemical Reactions; Elementary SchoolScience; Environmental Education; *Experiments;*Instructional Materials; *Plant Growth; PlantScience; Secondary School Science; Student Projects;*Teaching Guides

Seven experiments are presented in this Science StudyAid to help students investigate the control of plant growth withcheMicals. Plant growth regulators, weed control, and chemicalpruning are.the topics studied in the experiments which are based oninvestigations that have been and are being conducted at the U. SAgricultural Research Center, Maryland. Each activity outlinesintroductory information, objectives, materials required, procedureto follow, results and/or observations, and interpretation of thefindings. In addition, precautionary notes regarding the use ofchemicals and a vocabulary list are given. The study aid is notintended to be a complete teaching unit, rather, a supplement to aregular program providing up-to-date, researctirelated. activities.(EL)

Chemical Controlof Plant Growth

WI, DEPARTMENT OF HEALTH,EDUCATION & WELFAREOFFICE OF EDUCATION

THIS 00comENT 1--44s BEEN REPRODUCED EXACTLY AS RECEIVED FROMTHE PERSON on ononNiznTioN ORIG-INATING IT POINTS OF VIEW OR °PIN-IONs STATED DO NOT NECESSARILYREPRESENT OFFICIAL OFFICE OF EDU-CATION POSITION OR POLICY

U.S. DEPARTMENT OF AGRICULTURE Science Study Aid No.-7

TEACHER'S INTRODUCTION

This Science Study Aid contains seven experi-ments. They are intended to help studentsinvestigate the control of plant growth withchemicals. Most of the materials needed can befound at home or in school. Those which mustbe purchased can usually be found locally.

The subject matter of this Science Study Aidis divided into three broad topics: (1) plant

growth regulators, (2) weed control, and (3)chemical pruning. Each topic is subdivided intotwo or three individual experiments. Theseexperiments are based on investigations thathave been and are being conducted at the U.S.Agricultural Research Center, Beltsville, Md.

Although it would be beneficial to study allthree topics, each one is independent and can beinvestigated as a separate activity.

Chemical Control of Plant Growth wasdeveloped by science teachers working withthe research staff at the U.S. AgriculturalResearch Center, Beltsville, Md. The experi-ments in this Science Study Aid have beentested in the laboratory and in the classroomsof cooperating teachers.

Science Study Aids are not intended to becomplete teaching units. They can supple-ment your regular program by providing youand your students with up-to-date, research-related activities. Science Study Aids are

designed for easy reproduction at the schoolor by the school system. They are publicinformationnot copyrightedand you mayreproduce them without authorization.

If you are not already on our mailing listand would like to receive single copies ofother Science Study Aids as they areproduced, write to: Educational ServicesBranch, Agricultural Research Center,Beltsville, Maryland 20705. Be sure to includeyour ZIP code number in your return address.

CONTENTS

Vocabulary

Precautions

Experiments with plant growth regulators ... . .... . ..

Page

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4I. Using gibberellic acid to stimulate plant growth

= = 6I. , Using M H-30 to prevent sprouting 9

III. Using AMO-1618 to inhibit plant growth 11

Experiments in weed control 13V. Killing weeds with chemicals 14V. Gentner herbicide evaluation method 15

Experiments in chemical pruning 17VI. Pruning trees and shrubs 18

VII. Pruning coleus and ivy 20

Bibliography= 22

Trade names are used in this publicationsolely for the purpose of providing specificinformation. Mention of a trade name doesnot constitute a guarantee or warranty ofthe product by the U.S. Department ofAgriculture or an endorsement by theDepartment over other products not men-tioned.

Washington, D. C. Issued December 1972

3:e by the Superintendent of Documents, US. Government P-inting OffiWashington, D.C. 20402 Pride 30 cents

Stock Number oloonos2

VOCABULARY

active ingredientthe chemical element orcompound in a product that is respon-sible for its effects.

annuala plant that completes its life cycle inone year.

bienniala plant that completes its life cyclein two years. The first year it producesleaves and stores food. The second yearit produces fruits and seeds.

carrierthe liquid or solid material added to achemical compound to facilitate applica-tion to whatever is being treated.

chemical namea name that indicates thecomposition of the compound and alsothe structure of the molecule in organiccompounds.

concentrationthe amount of active ingre-dient in a given volume of liquid or in agiven weight of dry material.

diluentany liquid or solid material used inthe preparation of a formula to dilutethe active ingredient.

growth regulatoran organic substance that iseffective, normally in minute amounts,in controlling or modifying plantprocesses.

herbicidea phytotoxic chemical used forkilling or inhibiting the growth of certainplants.

herbicide-resistant speciesone that is diffi-cult to kill.

p_ erenniala plant that lives more than 2years.

petiolesleaf stalks.p_ etri disha small, shallow container of thin

glass with a loosely fitting cover for platecult,Jr-e: in bacteriology.

phytotoxicpoisonous to plants.ratethe amount of active ingredient or acid-

equivalent of a herbicide or growthregulator applied to a given area.

soil applicationapplication of herbicidemade primarily to the soil surface ratherthan to vegetation.

solventthe component of a solution that dis-solves the other components.

toxicologya science that deals with poisonsand their effect on living organisms, withsubstances otherwise harmless that provetoxic under particular conditions, andwith the clinical, industrial, legal, orother problems involved.

weeda plant growing where it is not desired,

PRECAUTIONS

All chemicals described in this publicationshould be applied in accordance with directionson the manufacturer's label, as registered underthe Federal Insecticide, Fungicide, and Rodenti-cide Act. Specifications with respect to crop,amount of chemical, and time of applicationshould be strictly observed.

All chemical pesticides are toxic to some formof life. Their very toxicity is the basis for theiraction. The relative toxicity of a pesticide is de-termined by testing it with laboratory animalssuch as rats. The animals are exposed to varyinglevels of the pesticide by different routes ofadministration. The amount of the pesticide thatcauses 50 percent of the test animals to die isknown as LD

50of the pesticide. The LD50 of

the pesticide to the test animal is expressed inmilligrams per kilogram body weight and also asacute oral, dermal or respiratory, representingthe route of administration. The lower thenumerical LD50 the greater the toxicity to thelaboratory animal tested.

Relatively toxic pesticides, as measured byanimal experiments, can be used in pest controlprograms when the amounts and directions foruse indicated on the label are followed. None ofthe chemicals used in the experiments describedin this Science Study Aid are either highly ormoderately toxic to laboratory animals. Thesechemicals can be used in these experiments withlittle or no hazard to the participants.

The following general precautions should beobserved in applying pesticides (herbicides andgrowth regulators) discussed in this SSA:

1. Read the label on each container beforeusing the contents. Follow instructions;heed all cautions and warnings. Store inclosed, well-labeled containers out of

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reach of small children and pets, andwhere the pesticides cannot contaminatefood or water.

2. Avoid inhaling vapors, dusts, or spraymists. Use a mask when specified on thecontainer label.

3. Avoid repeated or prolonged contact ofpesticides with the skin. Some individualsare hypersensitive to certain chemicalsand must be especially careful to avoidallergic reactions.

4. Wash hands and face thoroughly withsoap and water after each use of a pesti-cide. Do not eat, drink, or smoke untilyou have washed your hands and face.Wear synthetic rubber gloves and weargoggles where label instructions specify.

5. Avoid spilling pesticide concentrate onyour skin and keep it out of your eyes,nose, and mouth. If you spill any on yourskin, wash it off immediately with soapand water. If you spill it on your cloth-ing, launder the clothing before wearingit again.

6. Handle flammable chemicals with care toavoid ignition from friction, sparks, orcontact with combustible materials.

7. Avoid contaminating potable water sup-plies (as in wells) with pesticides.

S. Order only the amount of pesticide youwill need for an experiment. Companiesnormally supply larger amounts-than thatneeded for a few experiments and thelarge amounts they package are relativelyinexpensive. Therefore, try to arrangeorders for pesticides through the pur-chasing agent for your school. In thisway, one inexpensive order can serveseveral classes and provide enough chem-ical for many experiments.

9. After you have used up the pesticide youordered, wrap the empty container insheets of newspaper and put it in a plasticbag. Place this bundle in a brown paperbag and dispose of it in a trash container.

10. To dispose of a liquid pesticide solu-tion, dissolve a double portion of plain

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gelatin in the liquid. The liquid can be atroom temperature. Add more gelatin, ifnecessary, to hasten the solidifyingprocess. Then dispose of the solid mate-rials as directed in step 9.

11. Avoid spraying pesticides on plants otherthan those you are testing, or plants thatmight come within reach of children oranimals. Also, do not allow herbicides toget into open water where they might be-come available to pets, wildlife, or live-stock.

12. Do not use pesticide application equip-ment for any other purpose. When theexperiments are completed, discard theapplicators.

EXPERIMENTS WITH PLANT GROWTHREGULATORS

Scientists of the Agricultural Research Serv-ice, United States Department of Agriculture,are pioneering a new era in agriculture. It is thedream of these scientists that some day they willbe able to control plant growth as readily as wenow control electricity. They are finding,through extensive research, that certain chemicalsubstances can tell plants how or when to grow,to bloom, or to produce seeds. It may turn outthat nearly all functions of plants are chemicallycontrolled.

Discoveries made so .far have led to experi-ments in which chemicals are applied to plantsin an attempt to regulate the patterns of plantgrowth. Now, after a decade of testing and re-testing, scientists have come up with some verypromising plant- growth regulators. They havediscovered chemicals that will inhibit growth,stimulate growth, prevent blooming, and induceblooming.

This research was begun in response to thedemands of the buying public for shorter plants,for faster growing trees, for flowers that bloomat a particular time of the year, and for othernew types of plants. Although our scientists

have gained some control over particular growthfactors, there is still much to be learned beforewe achieve total chemical control over plants.

The following three activities are but a fewexamples of how a student can experiment withplant-growth regulators. These experiments areconducted primarily on beans, but the resultscan be applied to many other plants. Bean plants

provide the researcher with test organisms thatare readily available, easy to grow, and quick torespond to the chemicals being used.

Read all the directions carefully before begin-ning the experiments. After conducting theseexperiments as directed, you may wish to makeother, related investigations that will help you toformulate neW ideas about growth regulators.

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EXPERIMENT I:Using Gibberellic Acid to Stimulate Plant owtl

Several years ago, research scientists in Japannoticed that a compound derived from Asianfungus Gibberella fujilcuroi caused stem length-ening in several plants. Since then, scientistshave accumulated enough knowledge aboutgibberellic acid to make it usable by farmers andhome gardeners. This chemical, is now producedcommercially as a plant stimulator.

Objective:To determine- the effects of gibberciiicacid' on the development of plants by treat-ing several plants with the chemical and com-paring their growth with that of controlplants.

Materials:1, At least ten 4-inch flower pots or similar

containers,2. Potting soil or vermiculite.3. Gibberellic acid (a list of suppliers is en-

closed).4. Baby shampoo (to serve as a wetting

agent).5. Bean seeds (any species will work, but

several 'different species may be used forcomparison).

Procedure:1. Recording data: Obtain a notebook and

record all of your data, such as plantingschedule, chemical application schedule,and, most important, comprehensive re-ports of your results.

2. Planting: Plant the beans in the 4-inchpots or similar containers about 1/2 to 1inch beneath the surface of the soil. Afterthe beans are planted, mark the pots to

'According to the American Pharmaceutical AssociationJournal, vol. 48, No. 2, February 1959. pp. 127-130, whengibberellic acid was administered to mice orally at 15 grams perkilogram of body weight, no deaths occurred. The article said, insummary, that the "gibberellic acid was tested by various routesin mice for its acute toxicity and found to be essentially non-toxic."

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3.

4.

show whether they contain test plants orcontrol plants. This will save confusionlater when you apply the chemical. Youmay wish to treat half the plants and usethe other half as controls for comparison.If you want to make different applicationsof the chemical, you could use nine plants:three for one treatment, three for anothertreatment, and three as control plants.Light and temperature: Keep your pots

with planted seeds where they will be welllighted. A temperature of 80° to 85° P. isbest for germination of bean seeds. Keepthe plants moist throughout the experi-ment. If these conditions are met, theplants should be up in about 4 to 5 days; ifthe temperature is lower, germination maybe slower.Mixing gibberellic acid solution: Solutionsmade from a commercial formula shouldbe mixed according to the manufacturer'sdirections. If crystalline powder gibberellicacid is used, follow this procedure:

a. Dissolve 1 gram of powder in 5 mil-liliters of 95 percent ethyl alcohol.This will give you a basic concen-trate.

b. Add 1 milliliter of baby shampoo.c. Add the concentrated mixture to 1

liter of warm water. This prepara-tion contains 1,000 p.p.m, of gib-berel lic acid.

5. Treating the test plants: When the plantsare 8 to 10 days old, treat the test plant byspraying the solution of gibberellic acid, asprepared, on the stems and leaves. Use a

(bulb-type) hand sprayer for this proce-dure. Be careful not to spray the controlplants.lf conditions are right (that is iflight, heat, and moisture are normal asdescribed in 3 above) most young plantswit! show some response within 24 hours.

6. Treating the control plants: Spray controlplants with .a solution of 1 milliliter ofbaby shampoo in 1 liter of water. We adifferent (bulb-type) hand sprayer.

7. Length of the experiment: This experi-

P,5-ronr

SETTING UPTHE EXPERIMENT

Figure 1 - Test plants and control plants are needed for each chemical treatment. Tag each plant so that it can be marked andidentified during and after treatment.

ment can end 20 days or less after thebeans are planted. By that time, the testplants should exhibit observable effects ofgibberellic acid treatment.

Results:1. Compare the leaves of the control plants

with the leaves of the test plants. Note anydifferences in color.

2. Compare the leaf size of the controls andthe test plants.

3. Compare the height of controls and thetest plants to determine the effect of gib-berellic acid on the growth of beans.

4. As a last step in your experiment, remove

all the plants from their pots or containers,shake loose or wash away the soil or vermi-ct. lite, and examine the roots of the testand control plants. Observe- whether thetreatment had an effect on root size.

nterpretation:What can we conclude from the treatment ofbean plants with gibberellic acid? What partsof the plant were changed? How might chem-ical regulators in general, and gibberellic acidin particular, be used in agriculture? Can youdevise other experiments to investigate theeffect of gibberellic acid on plants other thanbeans?

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Figure 2 - A bulb-type hand sprayer is used to spray gibherelic acid on the stems and leaves of a test plant.

EXPERIMENT 11:Using M11-30 to Prevent Sprouting

Chemical regulators may be used to eitherstimulate or retard the growth of plants. Re-search scientists are experimenting with certainplant-growth retardants to prevent sprouting ofstored products, particularly carrots, potatoes,and onions. Unwanted sprouting of these vege-tables causes considerable cash loss to farmers,home gardeners, and wholesalers. The sprouts re-duce the market price, and shorten the storagelife of the vegetables, and may quickly makethem unmarketable.

Scientists believe that a suitable chemical thatwill prevent sprouting might be sprayed on vege-tables at the time they go into storage to preventpresent market losses and thus help to reducethe cost of vegetables to consumers. Mostsprout-inhibiting chemicals are still in the experi-mental stage. MH-30 is approved for use onpotatoes and onions. This research should provevaluable to commercial growers, food marketers,and homemakers.

In the following experiment you can investi-gate the effect of the chemical MH-302 on thesprouting of carrots, potatoes, and onions,which are stored in the dark. These three vege-tables often present a premature sprouting prob-lem. Many housewives have gone to their storagebins to find that their potatoes or onions havelong sprouts and are no longer usable.

MH-30 and other chemicals are being usedexperimentally to improve the storage life offruits and certain vegetables. This work is a goodexample of how basic research can lead to prac--tical advantages.

Objective:To determine the effectiveness of MH-30 inretarding vegetable sprouts by comparing thedevelopment of plants treated with the chem-ical to that of untreated plants.

2Diethanolarnine salt of 6-hydroxy-3--(2F1)-pyridazinone.

Materials:1. A cutting spoon used to cut balls from

melons.2. Sphagnum moss or fine quartz sand.3. Petri dishes or other shallow containers

about 10 cm. in diameter.4. A dark room where the temperature is

about 65° to 70° F.5. A cold storage -.free with a temperature of

40' to 500 F.6. Three grams of MH-30. (See list of sources

on page 20.)7. Unsprouted vegetables, such as carrots,

onions, or potatoes, which have experi-enced a rest period (see "Procedure").

Procedure:1. Preparation of vegetables.

a. Carrots Select medium-sized carrots foruniformity. Sever petioles so thatabout 1 cm. of each petiole remainsattached to each root. Remove and dis-card the lower part of the root fromeach carrot, saving about 1 inch of theupper part. Place these pieces in humidair at 40° to 50° F. for about 3 to 4days until they become suberose (theexposed bottom of the stub becomesca I I used).

b. Onions - Select small onions about 1 to2 cm. in diameter and of uniform shape.When you are ready to lay them in themoss or sand, peel the outer, loose scalesfrom the bulb.

c. Potatoes - Select tubers of medium size.Using a cutting spoon, remove sphericalpieces from the tubers so that each piececontains one eye. Place the pieces inhumid air at 40° to 50° F. for severalday_ s until they become suberose.

NOTE: Prepare about 20 to 25 pieces of eachvegetable so you have enough forboth your test plants and your con-trol plants. Prepare the carrots andpotatoes and allow them to suberizebefore peeling the onions.

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2. Mixing the MH-30 solution: Prepare yoursolution by mixing 1 milliliter or milligramof MH-30 in 1 liter of tap-water, (If youdo not have a scale for measuring out milli-grams, mix 1 part of MH-30 to 29 parts ofwater. For additional information, seedirections on MH-30 container.)

3. Treatment: Select 10 of each preparedvegetable for your test plants. Dip themmomentarily into the MH-30 solution.Allow to drain. Place the treated pieces onthe moist sphagnum moss or sand that youhave placed in the petri dishes. Do notcover the dishes.

4. Control Plants; Prepare 10 additional veg-etable pieces as control plants by dippingthem in water only and then placing themin petri dishes, as you did the test plants.

5. Storage: Place all of the dishes in a dark-ened room with a temperature of about65° to y0° P. Keep the moss or sandmoist.

6. Method of checking results. After the

control plants have developed a meas-urable amount of new vegetable growth,measure the length of the stem (sprout)and the fresh weight of the detachedsproutS. Compare these measurementswith similar ones for the treated materials.Record all of this information. For varia-tions on this .experiment, the following issuggested:

a. Leave sorr. .: control and treated plantsin a lighted ro-ini for comparison.

b. Teqt the experiment under differenttemperatures by placing some of thedishes in a warmer or colder place.

Interpretation:Discuss the importance of this experiment interms of the grower, the food store owner,and the homemaker. Discuss how MH-30could affect the cost of vegetables in thefuture, After you have been successful in thisexperiment, you may wish to test other spe-cies of plants.

EXPERIMENT III:Using Amo 1618 to Inhibit Plant Growth

The agricultural use of chemicals as growthinhibitors is becoming more important. Theyinhibit stem growth of a plant, or stop itsgrowth at a desired height. Research in this areais in answer to increasing demands for morecompact plants by crop growers, name gar-deners, and flower buyers.

Tall crop plants, ornamentals, sky-reachingshade trees, and shrubs that need frequent trim-ming and pruning, are common problems thatgrowers would like to overcome. The effort tofind scientific solutions to such problems ha3looked promising since 1949. It was then thatplant scientists of USDA's Agricultural ResearchService first reported organic chemicals thatwould dwarf a test plant without harm to theplant.

Although many different plant-shorteningcompounds have been tested, the followingexperiment deals with only one, Amo 16183,applied to a particular plant, beans.

Objectives:To determine the effects of Amo 1618 onbean plants by comparing the development oftreated and untreated seedlings.

Materials:1. Twenty or more 4-inch flower pots or sim-

ilar containers. (More pots may be used,but 20 is sufficient for good results.)

2. Potting soil or vermiculite.3. Disposable wood applicators, such as

toothpicks.4. 300 mg. of Amo 1618. (See list of sources

on page 20.)5. A liquid dish-washing detergent containing

polyoxethylene sorbitan monoluarate.6. Lanolin paste solution. (See item 4 under

"Procedure.")7. Bean seeds. (Any species will do for this

experiment)

1- piperidine-

Procedure:1. Recording data: Record all of your data,

such as planting schedule, chemical appli-cation schedule, and, most important, acomprehensive record of your results.

2. Planting: Plant the beans in the 4-inchflower pots or similar containers about 1/2to 1 inch below the surface of the soil.Water after plantin-g and keep the soilmoist to the touch.

3. Light and temperature: Keep the pottedplants in a place where they are welllighted. A temperature of 80° to S5° F. isbest to germinate the bean seeds. If light,heat, and moisture conditions are right,the seeds should germinate in 4 or 5 days.If the temperature is lower, germinationwill be slower.

4. Mixing Amo 1618 paste: To prepare a 1percent mixture of Amo-1618, place 25mg. of the chemical in a vial or test tubeand add 14 drops of the detergent. (If youdo not have a scale for measuring out 25milligrams, see directions on Amo-1618container.) Stir to dissolve the chemicaland then add 2 grams of lanolin. (Lanolincan be purchased at drugstores.) Melt thelanolin by putting the test tube in warmwater (not warmer than 131° F. or 55° C.)for a few minutes. Remove the test tubeand stir the mixture until it reaches roomtemperature and becomes semisolid. Thepaste is now ready for use.

5. Application: First allow all plants (testand control) to grow for 10 days. On the10th day, pair off the plants according tosize, putting similar sized plants together.Now is the time to mark and number yourtest and control plants. One way of marking is to put black tape on the controlplants and red tape on the test plants. Witha wood applicator, apply the paste in aband 3 to 6 mm. wide around the stem atthe first internodemidway between thefirst and second nodesof each red-taped(test) bean plant-in each pair.

TERMINAL BUD

SECONDNODE

Figure 3 - A wood applicator is used to apply pasta around the first internude = midway between the first and second nodes - of eachtest bean plant.

6. Allow all the plants to grow for an addi-tional 7 to 12 days.

Results and Comparisons:1. To determine the effect of Am -1618 on

bean plants, measure at time of applicationand again one week later. To do this, placea ruler at the node immediately above thetreated section of the stem. Then measurethe distance from this node to the tip ofthe terminal bud.

2 Measure the untreated (control) plants inthe same way.During the test, note any differences in the

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shape of leaves, stems, or other plant parts.You may find changes in color and othermodifications that have occurred becauseof the treatment.

Interpretation:What is the importance of growth regulatingchemicals for food production? What desir-able effects can the use of Amo-1618 bringabout in plants? What hazards could it pos-sibly create in the life cycle of a plant? Forfurther investigation into the use ofArno-1618, conduct the same test on otherplants, such as sunflowers and cucumbers.

EXPERIMENTS IN WEED CONTROL

A weed is a plant growing where it is notwanted. Man's struggle with weeds is as old asman himself. Weeds are persistent, and oftenprolific. They reduce crop yields, increase laborproduction costs, and interfere with efforts togrow food and flowers.

No part of man's food supply is immune tothe adverse effects of weeds. Production of foodfor man by marine life, wild animals, domestican imals, field crops, vegetable plants, wildplants, and other sources may be significantlyaffected by weeds. Weeds compete with cropsfor minerals, water, light, and essential nutrients.They may interfere with crop harvesting.

Man continues to suffer serious economiclosses from weeds despite many cultural,mechanical, and biological control measures athis disposal. Because of the need for more effi-cient control methods, the use of chemicals forweed control has grown rapidly since 1945.

New herbicides are developed by both Gov-ernment and industrial sc:antists, quite often in

joint projects. Before a herbicide is released bythe United States Department of Agriculture forpublic use, it is tested repeatedly for its useful-ness and safety in relation to plants, animals,and man. To prevent the pollution of our val-uable soil resources, the Department conductstests to determine what happens to the herbi-cides after they enter the soil. The cost oftesting and developing a single formula usuallyruns between 5 and 7 million dollars.

Cultural, biological, and chemical weed con-trol is essential to efficient food production. Thedevelopment of sound weed control practices re-quires the cooperative effort of many researchdisciplines.

These disciplines include the fields of organicchemistry, biochemistry, plant physiology, agro-nomy, horticulture, aquatic biology, ecology,agricultural engineering, analytical chemistry,m icrobiology, soil science, biometrics, andanimal physiology. Through knowledge gainedin these fields of study, man may some day winthe struggle against weeds.

EXPERIMENT IV:Killing Weeds With Chemicals

Certain chemicals can kill one plant and yetbe harmless to another. Hence, we can spray cer-tain vegetable crops to destroy the weeds aroundthem without injuring the crop itself, In the fol-lowing experiment, beans will represent thevegetable crop and ryegrass the weed.

Objective:To determine whether a certain chemical isselective in killing weed-grasses by applyingthe chemical to flats planted with two dif-

. ferent kinds of plants and comparing develop-ment to untreated plants.

Materials:1. Three wooden greenhouse flats (boxes)

about 18 inches by 24 inches and 4 to 6inches deep.

2. Potting soil or a mixture of soil and vermi-culite.

3. One 1-gallon jug with a cap.4. Bean seeds and ryegrass seeds.5. Herbicide containing trifluralin.6. Rubber bulb-type hand sprinkler.7. Graduated 50 ml. cylinder.

3rocedure:1. Fill three greenhouse flats with soil and

label the flats A, B, and C.2. Plant a row of beans across the length of

each flat 1 to 1-1/2 inches deep.. Sprinklethe ryegrass over the remainder of the flatand carefully work the grass seed into thetop 1/2 inch of soil.

3. Prepare a trifluralin concentrate by meas-uring 6 ml. of trifluralin solution into agallon jug. Add water to fill the bottle andshake vigorously.

4. Flat A is the control flat. Sprinkle, asneeded, with water onlydo not use tri-fluralin on this flat.

5. Flat B will represent the proper applica-tion of herbicide on vegetable crops. In the50 ml. cylinder, mix 12.5 ml. of trifluralinconcentrate from the jug with 37.5 ml. ofwater. Using the rubber bulb-type handsprinkler, apply 50 mi. of this diluted con-centrate to each square foot of soil sur-face. This amount is equivalent to applyingthe chemical at 1 lb. per acre. If the samebulb is used to apply both concentrations,(see item 6), the lower concentrationshould be applied first.

6. Flat C will represent over-application ofherbicides. Apply 50 ml. of the trifluralinconcentrate to each square foot of soil sur-face. This amount is equivalent to applyingthe chemical at 410. per acre.

7. In applying the herbicide concentration,use the bulb-type sprinkler to spray thesolution uniformly over the soil surface.Be sure to wash the sprinkler several timesafter using it to attempt to remove alltraces of the herbicide.

8. Cover the treated area in the three flatswith about 1/4-inch of finely sifted pot-ting soil. Water by gently sprinkling thesurface whenever the soil needs moist-ening. Beans in the flats should germinatein about 4 to 6 days. The ryegrass in FlatA should come up at about the same time.

Results and Comparisons:1 Measure and compare the growth of beans

in each of the three flats.2. Measure and compare the growth of the

ryegrass in each of the three flats.3. Observe and determine which flat shows

competition between the beans and theryegrass.

Interpretation:Define a herbicide. Explain what desirableeffects can be brought about with the properuse of herbicides. What undesirable effectscan result from improper use: After you havebeen successful in this experiment, test theherbicide on other species of plants.

EXPERIMENT V:Gentner Herbicide Evaluation Method

Dr. W. A. Gentner of the Agricultural Re-search Service has developed a simple method oftesting a variety of plants and herbicides byusing test tubes instead of flower pots or con-ventional containers. This technique enabledhim to study many plants at one time and towatch the progress of each plant more closely.

Objective:To compare the effects of various herbicidesand various concentrations of herbicides onfive different types of plants in test tubes.

Materials:1. Test tubes or funnels (5 for each seed

tested).2. Dri11,1/4-inch, with sanding disc (optional).3. Glass wool (angel hair).4. Goggles, protective (optional).5. Quartz sand.6. Respirator (optional).7. Rubber collars (or some similar device)

to hold test tubes or funnels abovebeakers.

B. Beakers (5 for each seed tested).9. Nutrient solution. (Any liquid plant food

purchased at a local supply shop will besufficient. Follow the manufacturer'sdirections.)

10. Herbicides to be testedfor example, tri-fluralin, atrazine, diuron, molinate. Thesechemical names will appear in the state-ment of active ingredients on the label.Ryegrass, corn, lettuce, mustard, andradish seeds.

Procedure:1. Set up five test tubes or funnels for each

plant species you plan to use. Four will beexperimental and one will serve as a con-trol. If test tubes are used, rub the bottomof each tube with a sanding disc on 1/4 -

inch drill until a small hole forms. This

process takes time and patience. Forsafety, use a respirator and goggles.

2. Mix the nutrient you will use as a test solu-tion. To this, add a concentration of theherbicide to be tested. Use concentrationsranging from 0.1 p.p.m. to 5.0 p.p.m. (Seestep 6, below.)

3. Place rubber collars (or similar devices) tohold test tubes above the beakers. Iffunnels are used, put them in rings, attachto ringstand, and place over beakers.

4. Place 3/4-inch wads of glass wool (angel _

hair) in bottom of test tubes or funnels.This wad will keep the sand from flowingthrough the base hole of the test tube orfunnel.

5. Half fill the test tubes or funnelsquartz sand.

6. Place nutrient solution and different con-centrations of herbicides in four of thebeakers. In the fifth beaker, add only thenutrient solution. Be sure to mark eachbeaker properly.

7. Plant two or three seeds 1/4-inch deep inthe sand of all test tubes or funnels.

8. Suspend the test tubes or funnels over thebeakers containing solutions to be studied.Once a day, immerse the tubes or funnelsinto the solution so as to saturate thequartz sand. Raise the tubes or funnelsafter saturation so that they do not con-tact solutions in beakers.

9. Record all data about the plants includinggrowth rate, shape of leaves, length ofstems and roots, and concentration ofherbicides.

ith clear

Interpretation:What differences did you observe between ex-perimental and control plants? How can thisexperiment be useful to industry? How canthis experiment be important to the farmerand home gardener? Continue your researchby exposing more plants to different herbi-cides. Also, test different concentrations ofherbicides to find the safest levels of herbi-cideitolerated by each test species.

TEST TUBE WITHBASE GROUND AWAY

RUBBERBAND COLLAR

PLASTICCOFFEE-CAN LID

GLASS WOOL

SOLUTION

HOLE IN BOTTOMOF TEST TUBE

Figure 4 - A simple test tube stand.

EXPERIMENTS IN CHEMICAL PRUNING

In many areas, the lack of garden space hasbecome a problem for the amateur horticul-turist People live in crowded conditions wherewastes often pollute the air and soil. Green,growing things have a difficult time.

Trees grow too high and shrubs spread outtoo much for an apartment balcony or even asmall yard. Horticulturists are conducting exper-

iments on chemical pruning which may help tosolve this space problem.

Chemical pruning means that certain plantsand trees can be sprayed with a chemical to con-trol their size. Eventually, even with the smallestyard or garden box, we will be able to enjoy thesurroundings created by growing trees andshrubs. So far, however, chemical pruning is stillin the experimental stage. Extensive research re-mains to be done before pruning chemicals arereleased to the public.

EXPERIMENT VI:Pruning Trees and Shrubs

The following experiment will allow a studentresearcher to conduct some basic study withpruning chemicals either at his home or atschool. Please read all directions carefully beforestarting the experiment. The experiment re-quires at least 6 weeks to complete and thechemical kits must be ordered in advance.

Objective:To compare the effects of various concentra-tions of chemical pruning agent on differenttypes of trees and shrubs.

Materials:1. Chemical pruning agent kit, which can be

ordered from either of the following ad-dresses:

Emery Industries, Inc.4300 Carew TowerCincinnati, Ohio 45202

Proctor & Gamble Industrial Soap& Chemical Products DivisionCincinnati, Ohio 54217

2. Waterproof tags and magic marker:3. A throat atomizer or similar device with

which you can spray a fine mist on yourtest plants.

4. Two pieces (for each tree or shrub to betested) of plastic film, each about 3 squarefeet, to use as shields while spraying.

5. Several available trees and shrubs.Examples_: trees (deciduous)elm,maple, birch, and others; shrubsprivet,pyracantha, azalea, and others; coni-fersany species.

Procedure:NOTE: This experiment can be either a long

or a short-range project. By making it a long- 5.range project you can conduct tests during thefall, winter, and spring. This will enable youtheresearcherto determine the proper time of yearfor applying chemical pruners. If a short-rangeproject is desired, start about 'March 1 and test

every other week for six weeks. In morenorthern areas, April 1 will be a more satisfac-ory starting time.

1. After receiving the pruning agent from themanufacturer, mix various Concentrationsfor use in your test. If you try a 3-percent,4-percent, and a 5-percent concentrationyou may be able to determine the properdosage for different species.

2. In your home yard or on the schoolgrounds, select trees or shrubs that youhave decided to test for chemical pruning.(See general precautions on page 3 whichshould be observed in applying pesticides.)Select a control branch from the same treeor shrub for each branch you are testing.Remember that you are going to spray thetip of the selected branches.

3. Tag each branch that you have selectedwith the following information:

4.

Name of plant:Concentration:Date:Time:Temperature:

(Example)Privet2 percentMay 5,19712:30 p.m.(If desired)

Record the same information in a datebook and leave enough space to describethe reaction of the plants to the chemicalpruner. Tag and test as many differentspecies of plants as possible.

Preparing the shields: Use sheets of plasticfilm to protect the rest of the tree or shrubwhen you are spraying the branch tips thatyou have decided to test. One sheet shouldhave a slit so you can slip the sheet overthe branch between the area to be sprayedand the remainder of the branch. Place theother sheet below the branch to besprayed.After placing the shields on the tree, orshrub, you are ready to spray the branchtips. Using the atomizer or similar device,spray the leaves and twigs in front of theshield with a fine mist. Be sure to wetthem to the point of runoff. Remember to

treat at least several branches on each treeor shrub. Treat at least one plant in eachgroup_ : deciduous trees, shrubs, and coni-fers. Mark control branches but do notspray them_

6. Watch for reaction in an offshoot of a twig.The first sign will be the blackening of thenewest leaf on the twig. Later this blackportion will dry and turn brown. Reac-tions will start in as early as one hour withsome plants and as late as one day or morewith other plants. It is quite possible thatsome species will not react at all. Record,all reactions in your data book.

Observations:1. Compare the reactions of the three plant

groups: deciduous trees, shrubs, and coni-fers.

What group reacted most?What group reacted least?Did any group fail to react?What species reacted most?What species reacted fastest?What species reacted slowest?

2. Compare the different concentrations.a. What concentration worked best?b. What concentration worked least?

ISOLATING THE TREATMENT

SLIT

TO BE SPRAYED

THROATATOMIZER

PLASTIC

SHEET

Flgu e lestic film sheets are used to protec he rest of the tree when spraying the branch tips.

19

EXPERIMENT VII:Chemical Pruning of Coleus and Ivy

An exciting new possibility in plant control isnow in the experimental stage of developmentby the U.S. Department of Agriculture, at theAgricultural Research Center, Beltsville, Md. Inthis project, scientists are attempting to developreliable compounds to chemically prune. plants.Many plants, especially in commercial green-houses, require time-consuming and expensivehand pruning or pinching to develop the desiredproduct.

Horticultural scientists have developed andexperimented with several promising compounds. One of the most promising is a deriva-tive of fatty acids. The following experiment is abasic example of how the scientists have beentesting fatty acid emulsions for selective prun-ing. This project is still in the experimental stageand extensive research is being conducted toinsure positive results.

Objective:To test the selective action of chemicalpruning agents on house plants by comparingthe development of treated and untreatedplants.

Materials:1. Potted plants.

a. Potted coleus with tissue of variousages (an old plant).

b. Potted ivy with tissue of variousages.

c. Bean seedlings that are 7 to 10 daysold (start plants so they are thethe right age at the time of applica-tion).

20

NOTE: For each test plant select a controlplant of equal size and age.

2. A 1-quart hand-sprayer or a throat atom-izerer.Chemical pruning agent.

4. Growth-regulating compounds can be ob-tained from companies listed on page

5. A proper place to keep and spray your testplants as well as your control plants.

Procedure:1. Select your plants so that you have a test

plant and a control for each treatment.You may test as many plants as you like,depending upon what is available.

2. Tag each plant with a waterproof tag sothat it can be marked and identified duringand after treatment.

3. Select a warm, well-lighted place to keepyour plants during the experiment. It isbest to have two separate places, identicalin climate,one for your test plants and onefor the control plants. This will preventaccidental spraying of the control plants.

4. Prepare the pruning agent (Precau-tion: Do not inhale mist when spraying.In case of contact with face or eyes, washwith water. Keep chemical and spray ap-paratus out of the reach of small childrenand others not involved in the experi-ment.)

5. Dilution Chart

Dosage levelfluid ounces of chemicalper quart of emulsion

6.4- 4 3.6 2.9 2.5 2.1 2 1.7

Dilution ratio

1:4 1:7 1:8 1:10 1:12 1:14 1:16 1:18 1:20

a. Select a dosage level from the dilu-tion chart.Measure the required amount of thecompound. you are using into aclean quart container.

c. Slowly add an equivalent volume ofwater and stir or mix into a uni-form emulsion.While stirring, slowly add morewater to fill the quart container.Shake well. This will be the emul-sion with which you will spray your

test plants. Dosage: The moreplants that .you have, and the moredifferent concentrations that youexperiment with, the more interest-ing your experiment will be..

6. Spray the plants.a. One spraying should be all that is

necessary to produce effective reac-tion. Spray only the test plants.Soil should be wetted before spray-ing, but the foliage should be dry.

c. Avoid using any other chemicalsprays 48 hours before and after ap-plication.Best results are obtained with a finespray, but care should be taken towet each growing tip to the pointof runoff.

e. Ten to fifteen minutes after spray-ing, rinse the entire plant withwater to prevent damage from anoverdose. Be careful to prevent thewashed off pesticide from going onto the soil in the pot.

f. Room temperature during applica-tion should be 700 to 80° F. Neverspray the beans, ivy, and coleusthat are tagged as control plants.Remember that the beans must beyoung seedlings.

Observations:About one hour after spraying, compare thetest plants and the control plants.1. What has happened to the coleus and ivy

that were treated iv-tt the emulsion? Whydidn't this happen tc the entire plant?

2. What happened to tlit.1 bean seedlings?What is the difference beitheen the beansand the other test plants?

3. What tissue was affected in all plants,young or old?

4. What use can this experiment be to plantgrowers?

5. To continue the experiment, allow theplants to return to their normal life and-care for them as usual. Observe how eachplant grows as compared to the controlplants.

BIBLIOGRAPHY

Free single copies of the following publicationare available from the Publications Division,Office of Information, U.S. Department of Agri-culture, Washington, D.C. 20250. Please useyour ZIP code with your return address whenyou order:Plant Hormones and Growth-Regulating Sub-stances Agricultural Handbook No. 336.

The following Government publications arefor sale only. Send order together with remit-tance to the Superintendent of Documents,Government Printing Office, Washington,D.C. 20402._ can be made bycoupons which are sold by the Superintend-ent of Documents in the denomination of 5cents, postal money order, express order, orpersonal check. Currency may be sent atsender's risk.

Using Phenoxy Herbicides Effectively Farmers'Bulletin No. 2183. 20 cents.

Lawn Weed Control With Herbicides Home andGarden Bulletin No. 123. 15 cents.

The following publications may be of in-terest:"Present Status and Future of Plant RegulatingSubstances," Agricultural Science Review, VOL

4, Fourth Quarter, 1966."Chemical Pruning of Plants," Science153: 1382-1383."Growth-Regulating Substances as Herbicides,-The Botanical Gazette, vol. 108, No. 2, 1957.

The following U.S. Department of Agriculturefilms may be borrowed from film libraries atland-grant universities in the 50 States, the Dis-trict of Columbia, and the Territory of PuertoRico."Pests or Plenty""Chemicals and Compact Plants""Evaluating Herbicides"

SOURCES OF HERBICIDES AND GROWTH REGULATING COMPOUNDS

General growth - regulating compounds

Matheson Scientific of Maryland, Inc.19727 Tucker St.Beltsville, Md. 20705 .-

Nutritional Biochemicals Corp.26201 Miles Rd.Cleveland, Ohio 44128

Sargent-Welch Scientific Co..7300 N. Linder Rd.Skokie, Ill. 60076

Stansi-ScientificDiv. of F isher Sci. Co.1231 North Monroe St.Chicago, ill 60622.

Curtin Scientific Company4220 Jefferson Ave.Houston, Tex. 77023

1234 Parklawn DriveRockville, Md. 20852

Distillation Product IndustriesDiv. of Eastman Kodak Co.Rochester, N. Y. 14603

Velsical Chemical Corp.Research Dept.330 Grand Ave.Chicago, III. 60611

Will Corp. of MarylandBox 6195Baltimore, Md. 21224-

Herbicide compounds

atrazi neGeigy Chemical CorporationArds ley, N. Y. 10502

Polyscience, Inc.Paul Valley Industrial ParkWarrington, Pa. 18976

Tissue cultures and reagents

diuron Grand Island Biological Co.E. I. du Pont de Nemours & Company 3175 Staley Rd.Wilmington, Del. 19898 P. O. Box 68

Grand Island, N. Y. 14072molinate

Stauffer Chemical CompanyP.O. Box 760Mountain View, Calif. 94040

Radiochemicals, growth regulators andrelated compounds, tissue culture media:

Schwartz -Mann BioResearchtrifluralin Div. of Becton, Dickinson & Co.

Elanco Division Mountain View Ave.Eli Lilly and Company Orangeburg, N. Y. 10962Greenfield LaboratoriesBox 708 Chemical pruning agentsGreenfield, Ind. 46140

Gibberellie acid

Aldrich Chemical Co.940 West St. Paul Ave.Milwaukee, Wisc. 53233

2098 Pike St.San Leandro, Calif. 94577

10 Ridgedale Ave.Cedar Knolls, N. J. 07927

Sigma.Chemical Co.3500 DeKalb St.St. Louis, Mo. 63118

Amo-1618

CalbiochemP. O. Box 54282Los Angeles, Calif. 90054

E. C. GeigerHarleyville, Pa.

Emery Industries, Inc.4300 Carew TowersCincinnati, Ohio 45202

Proctor & GambleAgricultural Chemical SectionAS & CPD, Proctor & Gamble Co.lvorydale Technical CenterCincinnati, Ohio 45217

Prepared byInformation Division

Agricultural Research Service

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