Source Year: 2000

The morphological, hydric and biochemical characteristics of zygotic embryos at different stages of their development and of cotyledonary somatic embryos of H. brasiliensis were analysed. The minimum level of maturity required for a good conversion ability (from embryos to plantlets) was defined. Sixteen weeks after anthesis, the zygotic embryos had acquired a conversion ability equivalent to that of fully mature embryos (24 weeks after anthesis) and to that of somatic embryos. The conversion rates fluctuated between 50 and 60;. The water content, osmotic potential and turgor pressure of somatic embryos were comparable with those of 16-week-old zygotic embryos. The water potential was comparable with that of immature 13-week-old embryos. Partial dehydration of somatic embryos, accumulation of reserves began early in development (13th week of proteins and 15th week for starch). In the 16th week, they had equal protein and starch concentrations compared with fully mature zygotic embryos. However, they were much smaller than zygotic embryos (ratio of 1:30 fordry weight), and reserves were around 20 times lower than those of zygotic embryos. This characteristic was linked to the low vigour of plantlets formed in vitro and to the long time taken for full plntlet development.