Does the color of the light affect plant growth?

Question

How can I demonstate it for a science project?

Answer 1

Try to grow plants under colored filters.

Answer 2

From http://www.botany.uwc.ac.za/ecotree/photosynthesis/spectrum.htm

Chlorophyll does not absorb all the wavelengths of visible light equally. Chlorophyll a, the most important light-absorbing pigment in plants, does not absorb light in the green part of the spectrum. Light in this range of wavelengths is reflected. This is the reason why chlorophyll is green and also why plants (which contain a lot of chlorophyll) are also green. Note in the graph above that the absorption of light by chlorophyll a is at a maximum at two points on the graph 430 and 662 nm. The rate of photosynthesis at the different wavelengths of visible light also show two peaks which roughly correspond to the absorption peaks of chlorophyll a. Plants do not depend only on chlorophyll a in their light harvesting machinery but also have other pigments (accessory pigments) which absorb light of different wavelengths.

You can buy light bulbs with different colors (ie. wavelengths) like red, gree, UV. Control all the variables except for the light source (ie. plant size, amt and frequency of water and nutrients) and take measurements over time.