The scientists guessed that the new seedlings were sensing the presence of neighboring plants by detecting the characteristic color of light reflected sideways from leaves of the neighboring plants. That characteristic color contains a very small amount of red light and a larger amount of what is known to botanists as far-red light. To test their guess, the scientists in effect blinded some new seedlings to that far-red light by placing clear blue cylinders around their stems. The accelerated growth was reduced or abolished. This striking result suggests that light scattered sideways from adjacent leaves provides an early signal of competition to young green plants. The young plants react to the signal by accelerating their stem growth to get a head start in the race for light.