Comparing carbohydrate status during Norway spruce seed development and somatic embryo formation

The carbohydrate status of developing seeds of Picea abies was examined in order to provide a frame of reference for the evaluation of changes in carb ohydrate content in maturing somatic embryos of the same species. Samples w ere taken at weekly intervals from 12 May 1998 (estimated time of pollinati on) until 20 October 1998. The total non-structural carbohydrate content wa s high (approximate to 150-180 mug mg(-1) dry weight) at the time of the fi rst samples and the carbohydrate spectrum consisted of sucrose, glucose, fr uctose, and pinitol. A dramatic decrease in carbohydrate content took place from June 6 onwards, that was accompanied by changes in carbohydrate parti tioning to favor sucrose over hexoses and the disappearance of pinitol. Raf finose and stachyose were first detected on July 28, and their content grad ually increased thereafter. Isolated embryos and remaining megagametophytes were analyzed starting with September 1. Carbohydrate content was higher i n isolated zygotic embryo than in the rest of the seed, with a slowly incre asing fraction of raffinose and stachyose. Comparisons of presented data wi th the results of our previous study of somatic embryo carbohydrate status (Lipavska et al., 2000) revealed the following common features: (1) a decre ase in total carbohydrate content and (2) an increase in sucrose:hexose rat ios in developing seeds and embryonal suspensor mass. Marked differences we re observed in carbohydrate spectra: (1) somatic embryo development was not accompanied by pinitol accumulation in any phase; (2) mature zygotic embry os, in contrast to mature somatic embryos, contained raffinose and stachyos e. These observations will provide a solid basis for improvement of protoco ls for somatic embryogenesis in Picea.