Geotropism is a plant's movement in response to gravity. This effect on plants causes the roots to grow down into the soil, and the shoot to grow up into the sky. Geotropism causes a plant to move in this manner in the Earth's environment, no matter the orientation of the plant. Students studying geotropism can experiment with different parts of a plant to see the effects of gravity. Teachers can have students use these experiments to develop projects showing their research and conclusions.
The potted plants experiment is designed to allow students to visually observe the direct effects of geotropism on plants. Students need two potted plants, two pieces of cellophane, two small blocks of wood, and an evenly lit room. First students wrap the base of the soil and pots with cellophane. Students put the control plant right-side up on a table. The variable plant is placed upside down, balancing on the two blocks of wood. With an evenly lit room, the risk of phototropism is eliminated. Within a few hours, students can observe the plant's movement in response to gravity. Students can record their observations and research in tables and charts and present their findings to the class.
Roots and Shoots
The roots and shoots experiment is a lengthy procedure that allows students to research the effect of geotropism over three or four days. Students require bean seeds, a gas jar, blotting paper and a cork. The bean seeds need to be germinated by rolling a damp cloth around the seeds and leaving it for 24 hours. Once the seeds have germinated, choose the seedling with the straightest root and stem. Put damp blotting paper along the inside of the gas jar and pin the seedling by the cotyledons to the cork and place inside the gas jar. Place the cork so that the seedling is horizontal in the center of the jar, and put the jar into a dark room. A control seedling can be used to show the effects of geotropism on the horizontal seedling. Students can draw diagrams and record the results over a few days to demonstrate the plant's movement in response to gravity.
The seedling garden is a project designed to emphasis the effect of geotropism on the roots of radish seeds. Students will need a package of radish seeds, blotting paper, two petri dish containers, two rubber bands, clay, a pie tray and a permanent marker. Place damp blotting paper into the base of both petri dish containers. Then add four to six seeds in each dish. Place the cover on each dish, and wrap the containers with a rubber band. Label each container by writing number 1 and 2 on the covers. On each dish, label an up, right, down and left clockwise around the container. Students then mount two lumps of clay on the pie tray, and one and two containers on each clay mound. Dish 1 is placed perpendicular, with up facing up and down facing down. Dish 2 is placed with the up label facing to the right, and the right label facing down in into the clay. The pie tray is then placed in a dark room. Students observe the direction of the roots in the two containers to visibly detect geotropism. The dishes can be rotated over a week to show that the roots will in fact move in the downward direction, despite the dish's orientation.
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