PHYTOCHROME-MEDIATED PHOTOTROPISM IN ADIANTUM-CUNEATUM YOUNG LEAVES

Phototropism of young Adiantum fern leaves is induced by red light as well as blue light. The red light response is mediated by phytochrome. This is the first evidence of phytochrome action in diploid fern tiss ue. The blue light response is mainly mediated not by phytochrome, but probably by a blue light-absorbing pigment as in the case of almost a ll plants and fungi. The red light-induced phototropism becomes detect able within 2 hr after the onset of unilateral light. The highest bend ing rate is about 10 degrees/hr, which occurs between 3-5 hr after the induction of the tropic response. The bending region is about 6-8 mm from the highest point of the coiled crozier where the growth rate bec omes slow.