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Effect of Low Water on a Seedling Root System

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Updated on Aug 29, 2011

The purpose is to discover if low-moisture levels will cause the roots of radish seedlings to grow more abundantly than those grown in soil with high-moisture levels. A secondary purpose is to discover the optimum amount of water for radish seedlings.

Plants gather water and nutrients from soil through their root systems. Roots extend downward and outward to gather water. What if water is scarce? Will a plant's roots grow longer and will there be more of them, as they search for water?

Hypothesize that the root system of radish seedlings will grow more abundantly (more mass and/or longer in length) in soil where moisture is low compared to soil where moisture is high. Also hypothesize that a point exists beyond which any further reduction in moisture will not cause more root growth but, instead, will cause health damage to the plant.

  • Paper towels
  • Radish seeds (50 of them)
  • Ten 8-ounce plastic drinking cups
  • Potting soil
  • Kitchen teaspoon measure
  • Marker or pen and masking tape
  • Water
  • Several weeks of time

Germinate 50 radish seeds by covering them between layers of paper towel and keeping them warm and moist for several days.

Once the seeds have germinated and begin to sprout roots and stems, select 30 of the best seedlings and discard the rest.

Fill ten 8-ounce plastic drinking cups ¾ full of potting soil. Plant three seedlings in each cup.

Using a marker or a pen with masking tape, label each cup with a letter of the alphabet: Cup A, Cup B, Cup C, and so on through Cup J.

Group the cups: Cups A, B, and C make up Group #1. Cups D, E, and F make up Group #2. Cups G, H, and I make up Group #3. Cup J will stand alone.

Group #1 will receive water daily. Cup A will receive one teaspoon of water. Cup B will get two teaspoons. Cup C will get three teaspoons.

Group #2 will receive water every other day. Cup D will receive one teaspoon of water. Cup E, two teaspoons. Cup F, three teaspoons.

Group #3 will only receive water every third day. Cup G, one teaspoon. Cup H, two teaspoons. Cup I, three teaspoons.

The seedlings in Cup J will be kept soaked with water daily, adding enough water to keep the soil thoroughly wet.

We are using three seedlings per cup to increase our sample size, thus giving more credence to our results.

Set the cups in an area of equal lighting and equal temperature (room temperature).

After many weeks, remove the seedlings from their cups and rinse the soil off their roots. Compare the root systems of all the plants.

Was your hypothesis correct? Was there a point beyond which any less amount of water resulted in poor growth or healthy appearance of the plants? How was the health of the seedlings in Cup J? Is it possible to overwater a plant?

Write down the results of your experiment. Document all observations and data collected.

Come to a conclusion as to whether or not your hypothesis was correct.

Something More

If a house plant is consistently given water only down one side of the flower pot, will the roots eventually grow toward that side (hydrotropism)?