Photomorphogenic effects on in vitro rooting of Prunus rootstock GF 655-2

The morphogenic effect of different light wavelengths on in vitro rooting of Prunus insititia GF655-2 inrelation to the presence of napthaleneacetic acid (NAA) in the culture medium was investigated.Results of experiments in which plantlets were rooted in NAA enriched medium showed that thepresence of auxin induced rooting even in the dark after an initial lag period. Illumination of thecultures with Red light was as effective in promoting rooting as treatment with 0.5/~M NAA; Red wasmore active in stimulating rooting in the short term than was NAA. The pattern of root formationresulting from the addition of NAA appeared to dominate development under White, Blue and FarRed treatments. Although it was possible to correlate the rooting response to the phytochromephotoequilibrium induced by the light treatments used, there arises a possible interference of specificBlue absorbing photoreceptors.