red green plant — Photo Source: Nancy Schumann

Ever noticed that plant shoots (the parts we can see) tend to grow up and out? Ever examined a plant root to determine which direction it grows and why? If your student or child enjoys biology and vegetation, this science fair experiment that explores geotropism and the effects of gravity on a plant's direction of growth are sure to be a winner!

Geotropism

Plant movement, also known as a "tropism", is triggered by external stimuli. There are many stimuli that influence plant tropisms including sunlight, water, available nutrients, and gravity. For simplicity, this science fair experiment will focus on the effects of gravity on plant movement. In general, as can be observed, plants roots tend to grow downward, toward the center of the Earth, in response to gravity. This phenomenon is known as geotropism. At the same time, plant shoots tend to expand upward. Vegetation that grows in this manner is said to exhibit anisotropic growth. But what happens if a pre-germinated seedling (one with visible roots and stem) is planted horizontally? Will the effects of gravity hold?

Project Overview

This project will explore the effects of gravity on plant movement when the seedling has been "planted" horizontally instead of vertically. Students will germinate bean seeds and choose a test specimen that has straight roots and stem. Pinned horizontally to the cork of a gas jar, students will then place the jar in a controlled environment and make observations every hour.

For a helpful diagram, list of needed materials, and project instructions be sure to visit the full post at Science Fair Projects!

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