In Vitro Regeneration from Seedling Organs of Brassica oleracea var. italica Plenck cv. Green Comet II. Effect of Light Conditions and Explant Size

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Abstract
The calabrese cultivar Brassica oleracea var. italica cv. Green Comet was used in a study of the effects of various physical and environmental factors on growth and differentiation of seedling organs in vitro. The particular factors studied were explant size, light conditions during seedling growth and during explant incubation and high and low temperature preculture treatments. For all explants, frequencies of survival and differentiation increased with increase in explant size (e.g. 7 mm discs produced ten times more shoots per disc than 4 mm discs). Although seedling morphology was strongly affected by the different light regimes there was no consistent effect on the subsequent response of seedling explants in vitro. Shoot formation from leaf discs and hypocotyl segments was better at 30 μE m−2 s−1 than at 100 or 200 μE m−2 s−1 (white fluorescent tubes), but more shoots were formed on root segments at the high than at low light intensities. For all three types of explants, shoot production was better with Grolux light at 32 μE m−2 s−1 than with white light at 30 μE m−2 s−1. Experiments involving preculture at high (35 °C) or low (4 °C) temperature showed no consistent effects.