Light effects on alpha-amylase activity and carbohydrate content in relation to lipid mobilization during the seedling growth of sunflower [Helianthus annuus]
1997
Darbelley, N. (Universite d'Avignon et des Pays de Vaucluse (France)) | Razafindramboa. N. | Chambost, J.P. | Pavia, A.
The changes in alpha-amylase activity and in starch and free sugar content were investigated in correlation with lipid mobilization in Helianthus annuus during the first 15 days of seedling growth in discontinuous light and in darkness. Throughout the seedling development alpha-amylase activity increased more significantly in light than in darkness. It was always lower in cotyledons than in other tissues of the embryo axis. In both culture conditions, most of the transitory carbohydrates accumulated in germinating cotyledons were very likely synthesized by gluconeogenesis from the stored lipid breakdown. Nevertheless, in light-grown cotyledons, photosynthesis contributes to increase the carbohydrate levels. The study of several soluble sugars indicates that 1) sucrose stored in cotyledons of mature seeds was used at the onset of seedling growth,more rapidly in light than in darkness, 2) galactose and xylose, both involved as precursors of some cell-wall polysaccharides, remained at a very low level throughout the 15 days and 3) glucose, fructose and maltose accumulated in old etiolated cotyledons in contrast to what occurred in the light
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