22 Science and Children

hildren notice seeds and plants every day. But do theyreally understand what seeds are and how they are relatedto plants? Have they ever observed what is inside theseed? What happens to the “things” inside a seed when itgrows? What do plants need to grow, and what do they

Overlapping learning cycles take studentsfull circle from seed germination through

plant-growth inquiry experimentation.

By Ann Cavallo

Plants

Cneed to stay healthy? Through a sequence of three related learningcycles—exploring seeds, germinating seeds and monitoring plantgrowth, and devising plant experiments—third-grade students answerthese and other questions about plant growth and discover that newseeds are made from the plants they grow.

Though the activities in these learning cycles are not new, they areuniquely presented as connected learning experiences, with some cyclesoccurring simultaneously and various phases of exploration, conceptinvention, and concept application overlapping.

Bean BabiesAt the start of the activities, students are given a seed to draw, glue,or tape to the outside of a blank notebook—this is the introductionto the seed study. Students document what happens to their seedsin their “Seed Book,” recording observations and illustrating theseeds. The children may extend the content of their seed books bycreating new and imaginative adventures for their seed and bymaking illustrations on each page.

CyclingThrough

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24 Science and Children

After making the seedbook, s tudents beginthe first learning cycleby examining a seed andits various parts. I usel ima, po le , o r s t r ingbean seeds soaked inwater at least six hoursfor this activity. Soakingthe seeds makes theme x p a n d a n d r e a d i l yopen into two halves.A f t e r s o a k i n g , b e a nseeds are easy for chil-dren to open and ma-nipulate, and the seedparts are clearly visible.

S t u d e n t s w o r k i ngroups of two to three,placing the seeds onwhite paper plates andusing hand lenses to ob-serve the seeds up close.Using plastic knives andt o o t h p i c k s , s t u d e n t scarefully open the seedinto two halves along itsnatural line. Next, thechildren draw their seedsi n t h e i r s e e d b o o k s ,showing the main partsthey observed and label-ing each part with theirown label names.

The children noticethe outer covering of theseed, which they often call the “skin,” and this outercovering is easily removed after being soaked. In-side the seed, they observe what they call the“fleshy” part of the seed. These two parts are mosteasily seen, and usually the first to be observed bychildren. However, until the children look veryclosely, they either do not see the embryo, or theythink it is not relevant. When I encourage them tovery closely observe the inside of the seed (oftenusing a hand lens), they see two tiny leaves, thestem, and part of a beginning root. They are sur-prised and delighted when they realize that whatthey are observing is “a baby plant” inside the seed!

The Parts of a SeedNext, students describe what they have learned aboutseeds, and I introduce scientific vocabulary. First,each student group posts one of their drawings from

the exploration on the board (Figure 1). Nearly all oftheir drawings show three main parts:

1) An outer covering or “skin”;2) A thick, “fleshy,” white or tan colored part; and3) Something that looks like a “baby” plant, complete

with tiny leaves.

I then ask students questions about each part, begin-ning with the “baby plant.” “Why do you think it is ababy plant?” The students respond that they can seeleaves and might mention the stem or even somethingthat looks like a tiny root. We discuss how amazing it isthat a tiny plant is inside the seed.

Next, we move to the “fleshy” part of the seed. Stu-dents often say it looks like potato or pasta. The childrenoften associate the inside of the seed with a food source,because most have eaten some kind of bean. I ask, “Since

Figure 1.

Student drawing of the parts of a seed in learning cycle one.

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we found a baby plant inside the seed, what might wethink this fleshy part would be?” The students thinkabout the things a baby plant would need and soonconclude it must be food for the baby plant.

We then move to the seed covering. I ask, “What doyou think the covering on the seed does?” The studentsrespond that it is for protection, to keep the baby plantdry, to keep it warm like a coat, or to keep it safe.

I now introduce the scientific names of the three seedparts they identified:

• The embryo (baby plant);• The endosperm (food for the baby plant); and• The seed coat (seed covering).

Next, the students write a statement that describes theconcept they have learned; for example, The seeds weobserved have three main parts: an embryo, an en-dosperm, and a seed coat.

To apply the concepts they have learned in thislearning cycle, students observe and dissect other kindsof seeds, including corn, peas, and any other bean type.Students find, draw, and label the three seed parts of thenew kind of seed.

Bean BaggiesThe second learning cycle in this sequence helps chil-dren observe and explain what “happens” to the parts ofthe seeds as they sprout. To set up this exploration, eachgroup needs a one-gallon sealable plastic bag, a whitepaper towel, and five dry bean seeds (preferably thesame variety used in learning cycle one).

Have students add about 1 cm of water to the bot-tom of the bag and then place a paper towel inside thebag so it is touching the water. Staple a row about one-quarter to two-thirds up from the bottom of the bag,allowing some space between each staple. The stu-dents should then place the bean seeds inside the bagon top of the staples and seal the bag. Students will notneed to add more water or open the bag during thecourse of the exploration.

Next, the children tape their bags onto the classroomwall. If possible, the bags should be exposed to similarconditions for this particular learning cycle (variationsin conditions can be studied in later experiments). Thepurpose of using sealable plastic bags rather than plant-ing seeds in soil is so students can directly observe whathappens to the seeds each day. Every day, students aregiven about 10 minutes of class time to observe, draw,and record their observations in their seed books.

Seeing SeedsBecause the Bean Baggie exploration phase takes afew weeks to “complete,” the students also engage in

another learning cycle on seeds (Gerber 1995) duringthe days they are recording daily observations abouttheir plants’ progress and “waiting for the plants togrow.” In this seed learning cycle, students dissectvarious fruits and observe the numbers and kinds ofseeds they contain. One of the main discoveries thechildren make is that some fruits, such as green pep-pers, have many seeds, while other fruits, such aspeaches, have one seed. They also come to under-stand that each seed will produce the same kind ofplant as its parent.

Within a few days, the students observe theirbagged seeds growing larger and notice that either theseed coat is cracked but intact, or it fell off. Soon,students notice something stringy growing downwardout of the seed. In a few more days, students notice“hairs” branching out of the “string” they see growingdownwards toward the water.

In a few more days, the students notice the seed hassomething growing out of it in an upward direction. Iask, “What is happening to your seed now?” “Why doyou think the “shoot” or stem is growing upwards?” Thechildren typically respond that the seed is growing ashoot or is growing up toward light. In a few more days,the children will observe that the first seed leaves unfoldand the seed coat falls off (if it has not already done so),and a second pair of leaves also emerges.

Sprouted LearningAt this point, the children take their bags down andlay them flat on their tables. Sometimes studentsfind that one or more of their seeds did not sprout;sometimes they have put too much water in the bagand the seeds become covered with mold; some-times they put too little water, so their sprouts aresmaller than those of others. When the students doobserve “problems,” such as mold or lack of sprout-ing, I have them think and talk about “why”—an-other opportunity for the children to learn! (If somestudents’ bags have several seeds that sproutednicely and other students do not have any sproutsdue to mold or dryness, the students with manysprouted seeds can share one or more of theirsprouts with students who do not have any.)

Repeating the same procedures as described inlearning cycle one, the children again dissect soakedbean seeds, leaving the open seeds on the paper platenext to their seeds in the bag. With their sprouted seedsand dissected seeds side by side, the children comparethe parts of the seeds and discuss where the parts of thedissected seed are on the sprouted seed. The studentsdraw the dissected seeds and the young plant next toeach other in their seed books, with arrows pointing tocommon “seed” and “new plant” parts.

26 Science and Children

The students areamazed that all partsof the dissected seed

can be found in thesprouted seed.

Keywords: Plant growth

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Enter code: SC040502

The students are amazed that all parts of the dis-sected seed can be found in the sprouted seed. Thestudents describe the concept they have learned: The“embryo” has “sprouted” and developed into the threeparts of a plant—roots, which grow downward; stems,which grow upward; and leaves, which grow off stems.”I introduce the term germination to help students labelwhat happened to their seed embryos.

To follow up (as an application), students plant thegerminated seeds in soil. The children observe hownew plants develop from their original seeds, bringingthe learning cycle full circle while learning about the lifecycle of plants.

Seed ExperimentationIn the final learning cycle in this sequence, students usetheir knowledge from the second learning cycle to pre-dict what seeds need to grow. I guide students with suchquestions as, “What do we (humans) need to grow?”Typically, students say that food is important. I askthem to remember where we found the food in the seed,and they quickly recall that the seed has a source of food.The students also state that “water” is important.

Next, many students say that seeds need light (orsunlight) to grow. Some students argue seeds do notneed light, only a warm temperature or heat. So, Iwrite both “light” and “heat” on the board with ques-tion marks. Then I ask, “How can we find out if seedsneed light to germinate?” to bring us to our finallearning cycle in which students work in pairs todevise an experiment.

Through class discussion, students construct theirown explorations to test the question. The childrendecide we need a dark space and a light space, which Iprovide in the classroom. The students place equalamounts of soil in two cups (to about three-fourths full)and state that they need the same number of seedsplanted in each cup—usually three to five seeds.

Once students determine all the details of theexperiments, they label the cups and plant and wa-ter the seeds. Then, each student pair places oneplant in the light (near the window or under a grow

light) and one in the dark (in a closed cabinet orunder cardboard boxes).

As a class, we discuss how we will collect data on ourexperiment in a way that is consistent among students.With guidance, students decide to make a table torecord the date and time of observations and data suchas plant height (and perhaps width) at each observa-tion, along with drawings and descriptive information,such as color and texture, and important events, such aswhen or if new leaves appear or if a plant dies. Each daychildren observe, water, draw, and measure theirplants, recording all details in their seed books.

In about a week, emerging plants begin to appearin both cups. Plants growing in the light are green andlush, whereas those in the dark are pale and thin. Intime, the seeds in the light have grown tall—andthose in the dark have also grown quite tall, perhapseven taller than those in the light. However, plantsgrown in the dark do not look very healthy, nor dothey produce additional leaves or flowers. To avoidstudents’ forming misconceptions (e.g., that plantscan grow in the dark), it is important to continue theobservation period for about four to five weeks, untilthe seeds that germinated in the dark have shriveledup and fallen over—dead.

Germination: What It TakesOnce data have been collected, students place all theplants on their tables and take out the charts they madein their seed books. Each team makes a line graph oftheir (tallest) plant’s height on poster paper with

April/May 2005 27

gridlines (available at office supply stores) using twodifferent colors or line styles. The students make arrowson their graphs pointing out where/when additionalleaves may have appeared and also perhaps flowers andnew seeds. They also mark where the plant in the darkdied and fell over.

The graphs are posted and we make comparisonsand look for patterns among groups. Viewing ourgraphs, I ask, “Why did the plants in the dark actuallygrow taller than those in the light at first?” “Why werethe plants in the dark pale, while those in the lightwere green?”

The students realize that the plants grown in the darkneeded to use all of the endosperm in the seed to grow(because there was no additional source of food),whereas as soon as the plants in the light emerged fromthe soil, they could start making their own food (con-cepts for later plant learning cycles!), so they did not useup all of the seed’s endosperm.

The students construct and share their concept state-ment with the class: Plants do not need light to sprout orgerminate, but they do need light to stay alive, continueto grow, produce flowers and seeds, and remain healthy.

Plant ExperimentsFor concept application, I ask students which variableof seed germination and plant growth they want toinvestigate next. For example, some students may de-cide to study, “Which color of light is best for plants togrow?” Another team may wish to alter the amount oflight plants receive, that is, “How much light (duration)do certain plants need to grow?” So, they set up anexperiment in which they expose their plants to lightover differing periods of time.

Other teams may wish to return to the originalquestion of the exploration and determine whetherheat is important to a seed’s germination (now thatthey know light is not necessary). To find out, stu-dents may place planted seeds in different placeswith varying temperatures, such as the freezer and

refrigerator. These and other student-constructedresearch questions are open to experimentation. Themost exciting part of this learning cycle is that thestudents “own” it, making a powerful and meaning-ful learning experience for them.

Measuring Student LearningStudent learning can be measured throughout eachlearning cycle by reviewing and evaluating the dataand notes written in students’ seed books for under-standing and accuracy, including concept under-standing, data collection and measuring techniques,mathematical representation of data (as appropriate tograde level), and skill in areas of language arts. Thestudents are also evaluated on their presentations,teamwork, and group contributions.

In addition, students may rewrite, if needed, and“publish” their seed books at the end of the unit, addinga cover page with a title and their name as the author andillustrator. When completed, we spiral bind and lami-nate the books and the children read and/or presenttheirs to the class.

By engaging in this series of connected learningcycles, students will have constructed a strong foun-dation for learning more complex topics about plantsas they progress to higher grades. And, as impor-tantly, they will have a new awareness and under-standing of seeds and plant life that exists in theworld around them. n

Ann Cavallo (acavallo@wayne.edu) is an associate

professor of science education at Wayne State Univer-

sity in Detroit, Michigan.

ResourcesGerber, B. 1995. These plants have potential: A simple approach

to a complex concept. Science and Children (33)1: 32–34.Jordan, H.J. 1992. How a seed grows. New York: Scholastic.Marek, E.A., and A.M.L. Cavallo. 1997. The learning cycle:

Elementary school science and beyond. Portsmouth, NH:Heinemann.

National Research Council (NRC). 1996. National scienceeducation standards. Washington, DC: National Acad-emy Press.

InternetAnnenberg/CPB Learner.org: The Great Bean Bag Adven-

ture www.learner.org/channel/workshops/nextmove/beanview/index.html

Enchanted Learning: Label the Sprouting Bean Diagramwww.enchantedlearning.com/subjects/plants/label/sproutingbean

University of Illinois Extension: The Great Plant Escapewww.urbanext.uiuc.edu/gpe/index.html

Connecting to the StandardsThis article relates to the following National ScienceEducation Standards (NRC 1996):

Content StandardsGrades K–4Grades K–4Grades K–4Grades K–4Grades K–4Standard A: Science as InquiryStandard A: Science as InquiryStandard A: Science as InquiryStandard A: Science as InquiryStandard A: Science as Inquiry

• Abilities necessary to do scientific inquiryStandard C: Life ScienceStandard C: Life ScienceStandard C: Life ScienceStandard C: Life ScienceStandard C: Life Science

• The characteristics of organisms• Life cycles of organisms• Organisms and environment