Carbon partitioning in Norway spruce: amounts of fructose 2,6-bisphosphate and of intermediates of starch/sucrose synthesis in relation to needle age and degree of needle loss

Abstract

Intermediates involved in carbon partitioning between starch and sucrose [dihydroxyacetone phosphate + glyceraldehyde 3-phosphate (TP), 3-phosphoglyceric acid, fructose 6-phosphate (F6P), fructose 2,6-bisphosphate (F26BP), in addition to glucose, fructose, sucrose and starch] were analysed in lyophilized needles of Norway spruce (Picea abies L. Karst). Samples were taken from all distinct parts of first and second order branches and the analysed data related to season, needle age, needle position and degree of needle loss (control and class 2 approx. 30%–40% needle loss). Positive and inverse correlations of F26BP, an important regulator of carbon partitioning between starch and sucrose, and F6P or TP existed in all samples. F26BP levels were highest in developing needles and gradually decreased during maturation, which is possibly indicative of changes in the relative sink strength during development (switch from import to export of sucrose). In class 2 needles the amount of F26BP was significantly increased. Together with nearly unaltered levels of sucrose but only slightly decreased amounts of starch the results can be taken as evidence for impaired carbon export in our class 2 samples. The data are discussed with respect to needle development and a possible impact of both air pollutants and mineral deficiency at the location from which the samples were taken.