SOMATIC EMBRYOGENESIS OF PINUS-SYLVESTRIS

Embryogenic cultures (EC) of Scots pine (Pinus sylvestris L.) were ini tiated from immature embryos. Whole ovules were used as explants. The responsive period for initiation began just after fertilization and re mained throughout the development of first stages of early embryos. Th e main part of the embryogenic cultures were initiated by the time of cleavage polyembryony. Strong correlation was obtained between degree days and the responsive period. During subsequent years the experiment s were repeated in Finland and Sweden. In all cases the responsive per iod for initiating embryogenic cultures was the same, about two weeks after fertilization. In 1991-1993, a total of 138 clones of elite pine trees were tested for their ability to initiate embryogenic cultures. Of these, 33% were responsive under our experimental conditions. Base d on about 300 ovules per clone the number of embryogenic lines induce d by the responding clones varied from 0.2% to 9.0% of the explants. S everal nutrient media were found to be suitable for initiation and pro liferation of ECs. About half of the cell lines responded to abscisic acid by producing maturing embryos. The embryos reached full maturity in cultures of only a few cell lines. Some of the embryos that produce d roots were planted in soil and transferred to a greenhouse.