EFFECT OF LIGHT QUALITY ON THE GROWTH OF DUCKWEED, LEMNA MINOR L

The effect of colored plastic panels was studied on a model system, duckweed, Lemna minor L., to determine if light could control emergent aquatic plants. Wavelengths of incident light were controlled using three different colored plastics (red, green, and blue), for which the UV-visible spectrum was evaluated using a spectrophotometer. Plants were exposed to light passing through the plastic, and their growth was compared with ordinary light of the same intensity (100 μEs/m2/sec. as measured by a light meter). Temperature was maintained at 25° ± 0.2°C. Growth was measured by the number of fronds produced as a function of time, a relationship between frond count, fresh weight, and dry weight was established. Plants grown under green plastic (420–580 nm) and blue plastic (400–470 and 620–660 nm) grew less than control samples; plants under red plastic (550–700 nm) grew better than control samples.