This laboratory exercise will allow students to explore the impact that light, humidity and gravitational orientation has on the growth and development of plants through the germination and seedling phase of the plants life cycle.
In which students will learn that plants exhibit two patterns of growth based on the part of the plant that is growing. Growth of plant parts is called tropism and roots of the plant grow toward the earth (typically downward) while shoots of the plant grow toward a light source (typically upward). The growth toward the earth is called geotropism (gravitropism) while growth toward light is called heliotropism (phototropism or anisotropism). Regardless of the orientation of the germinating plant the part of the plant that is the root will always show geotropism and the shoot will always show heliotropism. Additionally, the part of the plant showing heliotropism while also change color into a green color (due to chloroplast) so that the plant is able to perform photosynthesis. The green color is important to understand that green is the wavelength of light that is not used by the plant for photosynthesis.