INFLUENCE OF IRRADIANCE ON IN-VITRO GROWTH AND PROLIFERATION OF VACCINIUM-CORYMBOSUM (HIGHBUSH BLUEBERRY) AND SUBSEQUENT ROOTING IN-VIVO

The effects of light on in vitro proliferation and subsequent in vivo rooting and acclimatisation of Vaccinium corymbosum were investigated. The shoots were exposed in vitro to different irradiances (total radiation ranging from 55 to 240 mu mol m(-2) s(-1)) for 7 to 60 days. In vitro growth and proliferation and the possible consequences on in vivo rooting were observed. As compared to the control treatment (55 mu mol m(-2) s(-1)), higher irradiances improved proliferation and rooting ratios only with short applications (7 days). Short but high (210 mu mol m(-2) s(-1)) exposures applied at the end of the proliferation phase increased in vivo growth and rooting of the shoots. The shoots treated with strong light for longer times (14 and 28 days) showed both inhibition of growth and red colour of leaves and sprouts, and were less vigorous when transferred in vivo.