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Plant Growth and Life Cycle

Lab Activity Overview


To observe the changes in a plants life cycle


A plant going from seed to seed goes through a number of stages


  • Observe seeds
  • Sow seeds
  • Thin/transplant/grow
  • Observe-measure-record


Part A Part B
Anatomy & Embryogenesis Pod-Seed Quantitative Relationship
Plant 1&2 Plant 3&4
Plant 1 is self-pollinated Cross pollinate plants
Plant 2 is cross-pollinated Measure pod production
At intervals, sacrifice flowers and developing pods Measure seed production
Dissect-observe development Observe-record

Accept or reject Hypothesis

Kit Materials

1 Packet of 50 Rapid Radish seeds
1 Growing/Watering system
1 Packet of Rapid Radish growth medium
1 Packet of fertilizer
40 Stakes and twis-ties
10 Pollinating brushes
40 Plant labels
10 Plastic pipets
1 Bottle of algae inhibitor (copper sulfate), 15 mL
1 Growing Guide
1 Teacher and Student Guide

Additional Materials

LightsSee Growing Guide
Measuring equipmentThis can be as simple or as complicated as you have available or see as necessary. You may use any, all, or any combination of the following: ruler, dividers, calipers, balance, oven, graph paper. scissors, forceps

Time Allotment

5-6 weeks: 10-15 minutes each class period for observations and measurements; 20-30 minutes on days of pollination and terminalization (for 3 days approximately 2 weeks after sowing the seeds); 1-2 class periods for introduction, setup, and planting; 1-2 class periods for harvest, cleanup, result tabulation, discussion.


To study the changes during a plants life cycle.

Group size

Sufficient materials are included for a class of up to 40 students representing up to 10 teams of up to 4 student researchers per team. The selected size of the research teams depends on class size, lab arrangement, and student maturity. Three students per group would work well.


The activity can be carried out as a growth monitoring exercise, or options A and/or B can be added at flowering (pollination/terminalization).

Planting/Sowing (Day 1)

  1. Moisten the medium in a pan or plate with a little water (perhaps half a cup to a cup) and knead the medium so that is about the same dampness throughout.

  2. Divide the class into groups/teams of three (no more than four per group, so each student can claim a plant of his or her own). Rep. 1 from each team should pick up a growing container and place medium in each of the four pots of the container. Rep. 1 should ensure that the pots are full without trying to stuff too much of the medium into the pot (light and fluffy is optimal). Repeatedly tapping the growing containers will help the medium descend into the pots without compressing it as pushing down would. Do not push down on the medium, forcing it into the pot. Tapping will allow the medium to fill any gaps, and ensure that it reaches the bottom of the pot. It needs to reach the bottom so that water can move from the mat to the medium during growth.

  3. Rep. 2 from each team should carefully get five or six seeds and four labels. It may be best to have a tape dispenser beside the seeds so that the student can stick the seeds to a short piece of tape to carry them back to the team. The team should carefully observe the seeds and record the observations.

  4. Back at the teams workstation, each member of the team should place one or two seeds in each pot. The fifth or sixth seed picked up in step 3 provides the second seed in one or two pots. The extra ones are sown to replace plants in pots where seeds do not germinate. If two seeds are planted, they should not be planted too close together since this might lead to damage of one or both during transplanting.

  5. Rep. 3 from each team should put water in a glass, beaker, cup, recycled soda bottle, or the like, take it back to the team workstation, and with fellow team members carefully water the seeds. Watering will cause the medium to "go down."

  6. Rep. 4 (or Rep. 1 if no fourth team member exists) can take the growing container to your workstation to place a pinch more medium on top of the seed. No more than about 1/8" (2-3 mm) of medium should be placed on the seed, i.e. the seed should be no more than about 1/8" deep.

  7. With a waterproof pen or pencil, students should write their name or teams name, the treatment, and the date on the label, and stick it into the medium at the edge of the pot. On the other side of the label they should write the plant number (1,2,3, or 4).

  8. Growing containers should be placed on the mat on the platform of the watering tray under lights.

Fertilizing (Weekly)

Each team should receive in a beaker, jar, etc. about 10 ml of the fertilizer solution, made by adding the supplied fertilizer to one liter of water. Each pot should receive a small amount (about 2.5 ml2 squirts from the supplied plastic pipets) once a week. Place the fertilizer solution on the medium, not on the leaves of the plant, since the solution may burn the plant.

Watering (Ongoing)

The watering tray needs to have plenty of water. The mat should be thoroughly wet initially, and the end that is into the water should go to the bottom of the watering tray. The tray will probably require filling about twice per week. Add about 2-2.5 ml (2 squirts with the plastic pipet) of the supplied copper sulfate solution to the watering tray to retard algal growth. Keep an eye on all potsif any one becomes dry, find out what the problem is (usually the medium in the pot is separated from the mat by an air gap), record this observation, and thoroughly water the pot.

Transplanting (Day 2 or 3, before day 5)

Any extra seedlings need to be transplanted to pots where the seed did not germinate or has not yet germinated. This should be done carefully. Have students make a small hole with forceps or a pencil where the seedling is to be planted; carefully extricate the seedling from the medium using forceps; place it gently into the hole; push the medium over the roots; and gently adjust the medium so that the seedling is secure. Having the seedling relatively upright would be optimal, but it is more important that it feels planted and that it suffers as little damage as possible.

Staking (1 day, about day 10 to 15)

Insert stake in the soil and prop the plant up against it, secured by the twis-tie. The twis-tie should be looped tightly around the stake a couple of times, but loosely around the tender stem of the plant at a node (point where leaves are attached to the stem) so that the leaves can help keep the plant in place.

Pollination and Terminalization (3 days, about day 15 to 20)

No pollination should be done until optional exercises A and B have been read.

When most of the plants have some open flowers, this is the time to begin hand pollination using the brushes. Students should swirl the brush around in the open flower, trying to pick up the pollen from the anthers. This should take only a couple of seconds. Then go to an open flower on a different plant and repeat the swirling, this time delivering pollen to the stigma of that flower while also picking up pollen from the anthers. Again it should only take a few seconds. The brush should next be taken to a different flower on the original plant and the process repeated.

Develop a system, such as starting with the bottom flower that is open, and work up the plants. Repeat this process for three days during peak flowering. After the three days, students should pinch off the tip of the plant above the last open flower with finger and thumb (or forceps or scissors). The buds or side branches that are developing in the axils (angle between the leaves and the stem) should also be removed although none may exist. Remove them if they do appear later.

This tip removal process is called terminalization. The aim is to force the plant to place its resources and photosynthetic product into the seeds that will develop as a result of the hand pollination that has just been undertaken. Otherwise, some of those resources will be shared with growth that is wasted (such as production of more buds and flowers that will not be fertilized and so will not produce seeds, since you will not be doing any more hand pollination).

Observations (Ongoing)

Follow Growing Guide. Fill in chart by measuring, counting, and observing over the life cycle of the plant. Be sure students record data so that they can estimate:
  1. Rate of change of height as a measure of growth rate,
  2. Time to appearance of first flower bud,
  3. Time to opening of first flower,
  4. Time to onset of senescence (plant looking like it is beginning to die - yellowing and dying lower leaves, an appearance of drying out and browning off beginning).
The above data or the data allowing the estimates and calculations of these times and rates can be done on all plants (four plants per team). However, the following two exercises are called optional since you can choose to have them do one or the other on a particular plant, but not both. The reason is that the meaningfulness of the optional quantitative exercise (optional exercise B) may be reduced if flowers and developing pods are sacrificed in the anatomy and embryogenesis investigations (optional exercise A). If you wish to do both, it might be best for two of the four plants per team to be randomly designated (perhaps by drawing numbers) as the anatomy and embryogenesis plants (E) and the other two designated as the pod-seed quantitative relationship plants (Q). This guide will proceed as though there are two E plants and two Q plants per growing container, but it is up to you! (You may even prefer to skip either the anatomy part of optional exercise A and focus on the self-incompatibility part, or replace optional exercise B with the self-incompatibility experiment that here is incorporated as part of optional exercise A).

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