Carbohydrate metabolism in Norway maple and sycamore seeds in relation to desiccation tolerance

The work reports on sucrose and oligosaccharide metabolism in Norway maple (Acer platanoides L.) and sycamore (Acer pseudoplatanus L.) embryo axes and cotyledons during seed maturation. Enzyme activities of sucrose synthase (SuS), sucrose phosphate synthase (SPS), acid and alkaline invertases, α-galactosidase and galactinol synthase (GS) were studied. These species are closely related, but differ with regard to seed tolerance to desiccation. Norway maple possesses strictly orthodox seeds, while sycamore seeds are recalcitrant. In contrast to sycamore, maturation of Norway maple seeds was associated with an increase in raffinose and stachyose concentrations and a decrease in sucrose to oligosaccharides ratios. Activities of SuS and SPS as well as α-galactosidase were higher in seeds of sycamore compared to Norway maple. The activity of GS in Norway maple seeds was higher than in sycamore and was coincident with increased level of raffinose and stachyose in mature seeds. The results confirmed a finding of increased sucrose metabolism during maturation in recalcitrant sycamore seeds compared to orthodox Norway maple seeds.