Plant growth environment effects on rapeseed microspore development and culture : a flow cytometric study

The influence of donor plant growth conditions on microspore embryogenesis in rapeseed (Brassica napus) was studied for plants grown at 23/18 degrees C (16/8 hours) under continuous light, 23/18 degrees C (16/8 hours) with a light/dark (16/8 hours) cycle, 15/12 degrees C (16/8 hours) under continuous light and 15/12 degrees C (16/8 hours) with a light/dark (16/8 hours) cycle. Significantly higher embryo yields were obtained from microspore cultures initiated from donor plants grown at 15/12 degrees C instead of 23/18 degrees C. Flow cytometric measurements of the microspores isolated from 2.5- to 5.0-millimeter buds showed that the microspores isolated from low-temperature-grown plants had significantly lower log 90-degree light scatter to forward angle light scatter and log 90-degree light scatter to time of flight ratios than those isolated from high-temperature-grown plants, suggesting that the former are more translucent than the latter. Thus, the effect of donor plant growth temperature on microspore embryogenesis may be mediated by a change in the physiology of the microspore cell, which results in the reduction of its cytoplasmic granularity and/or exine density.