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Botany Science Projects - Learn about plant growth
by Science Made Simple

Botany and Plant Growth Science Projects

1. What affect does the brightness of light have on the growth rate of a plant?

How do light and dark conditions affect the germination and growth of seedlings?

Materials: Greenhouse or sunny window sill, 10 bean seeds, 10 small pots, water, ruler, potting soil, pencil.

Procedure:

  1. Fill the 10 small pots with equal amounts of dampened potting soil.
  2. With a pencil, make holes about 2 centimeters deep in each pot.
  3. Place the 10 bean seeds, one per pot, and cover the seeds with some of the soil.
  4. Place 5 of the pots in the greenhouse or on a window sill on the sunny side of the house.
  5. Place the other 5 on a window sill that does not receive bright sunlight.
  6. Be sure to water the plants as needed.
  7. Seeds will germinate within 7 days, and you can begin making stem measurements. Take stem measurements for 14 days. Note the difference in stem length for each set of plants, and write down your observations.

Results: What differences did you observe between seedlings that grew in the bright sunlight compared to less bright light? (color of leaves, length of stems, etc.) What caused those differences?

2. How do different types of fertilizers affect plant growth?

Fertilizers differ in their amounts of the nutrients nitrogen, phosphorus and potassium. Get different fertilizers from a garden shop or nursery and apply them to groups of the same plant. Do the different fertilizers change how the plants grow? You could measure height, width, number of leaves, how fast the plants grow, number of flowers or yield.

3. Which way is up? - Tropism and Auxin

Many seeds and bulbs have a definite top and bottom. What happens if you plant them upside down or sideways? Will the seeds still grow; will it take longer for leaves to start showing up?

What happens if you change a seed's direction once it starts to sprout? You'll learn about the chemical auxin, which affects where roots and stems grow.

Procedure:

  1. Divide 10 bean seeds into 2 groups of 5. - a control group and the experimental group.
  2. Spread the seeds out on moist paper towels then wrap them a pieces of folded aluminum foil.
  3. Label one side of control group packet "Up". Label the sides of the experimental group "A" and "B". Place the sprouts where they will not be observed.
  4. Allow the beans to sprout for 3 days.
  5. Carefully open the foil and towels and observe the seedlings. Moisten the towels if necessary, then refold the foil. Turn the experimental set of the seeds upside down. Make sure to keep the control seeds right-side up.
  6. Open and observe the sprouts every 2 days, making sure to keep the control sprouts right-side up and turning the experimental group over.

If you have access to an old record player turntable, you can take it a step further by using it to simulate changing gravity's pull on seeds. Tape the experimental packet onto the turntable and set it for 78 RPM. Allow the machine to rotate continuously for 5 days. After the 5 days are up, turn off the record player and without changing the position of the foil, open them up and observe the beans. The rotating turntable creates a gravity with an outward force instead of the normal down.

4. What happens when you grow sweet potatoes next to other plants? - Allelopathy

Compare how fast other plants grow at different distances from sweet potatoes. Remember to grow some control plants nowhere near the sweet potato.

Background Info: Allelopathy is a chemical process that a plant uses to keep other plants from growing too close to it. Some plants that use allelopathy are black walnut trees, sunflowers, wormwoods, sagebrushes, and trees of heaven.

There are several ways in which an allelopathic plant can release its protective chemicals:

  • Volatilization - Allelopathic trees release a chemical in the form of a gas through small openings in their leaves. Other plants absorb the toxic chemical and die.
  • Leaching - Some plants store protective chemicals in the leaves they drop. When the leaves fall to the ground, they decompose, giving off chemicals that protect the plant.
  • Exudation - Some plants release defensive chemicals into the soil through their roots. Those chemicals are absorbed by the roots of other nearby plants, which are damaged.

Fruit Ripening

5. How do different conditions affect the speed at which fruit and vegetables ripen?

Temperature, light, placement in sealed bags, exposure to other ripe fruit--all have different effects on different fruits and vegetables. Design an experiment to test two or more of these variables.

Background Info: Ethylene gas is the ripening agent that many fruits and vegetables produce naturally. Ethylene causes them to ripen--and then overripen. While refrigeration and humidity slow the effects of ripening, they don't stop the production of ethylene gas.

The more the fruit ripens, the more ethylene gas it makes. This has a big effect on how--and when--farmers harvest their fruits and vegetables for market. Most commercial tomatoes are picked before ripening is completed, so the fruit won't spoil before it gets to your market. But picking early also means the tomato spends less time on the vine, where ethylene would help build more of the sugars and acids that create tip-top tomato flavor.

Soil pH

6. The effects of light on seedlings germination

How do light and dark conditions affect the germination and growth of seedlings....

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