Loss of tolerance to desiccation in germinated Norway maple (Acer platanoides L.) seeds. Changes in carbohydrate content

Carbohydrates were analyzed in Norway maple embryo axes and cotyledons after imbibition, in the middle of cold stratification, before germination and during radicle protrusion to 8-10 mm and 20-25 mm. Simultaneously desiccation tolerance of seeds was determined by tetrazolium (TTC) test, after desiccation of seeds to 10-20% of water content. The cotyledons were tolerant to desiccation throughout all stratification and germination period. Embryo axes became sensitive to desiccation when hypocotyls-radicle protrusion reached 20-25 mm length. In this period the significant increase of monosaccharides: glucose, fructose and galactose in embryo axes occurred. This was not observed in cotyledons. During the germination period significant decrease of sucrose and raffinose content was noted in embryo axes and cotyledons. Relatively less changes appeared in stachyose content in embryo axes while in cotyledons it decreased evidently. The mass ratio of sucrose to oligosaccharides was higher in cotyledons of germinated seeds. The marked decrease of mass ratio of oligo to monosaccharides was observed in embryo axes in the last period of germination. The role of carbohydrates in loosing tolerance to desiccation in germinated Norway maple seeds is discussed.