Effect of Monochromatic Light on Anthocyanin Content in Seedlings of Benitade (Polygonum hydropiper L.)

Abstract

Seedlings of benitade, Polygonum hydropiper L., were irradiated with eight kinds of monochromatic light in the range of 400-730nm for different periods of 1 hour, 9 hours, 3 days and 5 days, at the intensity of about 9Jm^-2s^-1.
The anthocyanin content per plant was higher at 665-700nm (red region) on 1 hour irradiation, and at 400-460nm (violet-blue region) and 700-715nm (far red region) on 9 hours irradiation, respectively. Although anthocyanin synthesis was most promoted both at 400-460nm and 665-700nm on 3 days irradiation, two peaks were evident at 460 and 665nm, the latter being 30% higher than the former, on 5 days irradiation. Except on 1 hour irradiation, the anthocyanin content was the least at 560nm (green region).
The seedlings were irradiated for 30 or 60min alternately with red and far red light with relatively broad wavelength at the intensity of about 6 and 4Jm^-2s^-1, respectively. In addition, alternate irradiations with red and far red light for 5min each, per hour, was intermittently repeated 7 times. The stimulating effect of red light on anthocyanin synthesis was lost on subsequent irradiation of far red light, however, it was recovered again with re-irradiation of red light. From these results, it seemed that one of the photoreceptors for anthocyanin synthesis in Polygonum would be a phytochrome.