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 carbohydrate content in maturing somatic embryos of the same species. Samples were taken at weekly intervals from 12 May 1998 (estimated time of pollination) until 20 October 1998. The total non-structural carbohydrate content was high (≈150-180μg mg-1 dry weight) at the time of the first samples and the carbohydrate spectrum consisted of sucrose, glucose, fructose, and pinitol. A dramatic decrease in carbohydrate content took place from June 6 onwards, that was accompanied by changes in carbohydrate partitioning to favor sucrose over hexoses and the disappearance of pinitol. Raffinose and stachyose were first detected on July 28, and their content gradually increased thereafter. Isolated embryos and remaining megagametophytes were analyzed starting with September 1. Carbohydrate content was higher in isolated zygotic embryo than in the rest of the seed, with a slowly increasing fraction of raffinose and stachyose. Comparisons of presented data with the results of our previous study of somatic embryo carbohydrate status (Lipavská et al., 2000) revealed the following common features: (1) a decrease in total carbohydrate content and (2) an increase in sucrose:hexose ratios in developing seeds and embryonal suspensor mass. Marked differences were observed in carbohydrate spectra: (1) somatic embryo development was not accompanied by pinitol accumulation in any phase; (2) mature zygotic embryos, in contrast to mature somatic embryos, contained raffinose and stachyose. These observations will provide a solid basis for improvement of protocols for somatic embryogenesis in Picea