Wednesday, April 02, 2008

Seasonal photosynthesis and partitioning of non-structural carbohydrates in Euphorbia esula L.


Previous evidence indicates that changes in well-defined phases of dormancy in underground adventitious buds of leafy spurge in late summer and autumn are regulated by complex sensing/signaling pathways involving aboveground sugar signals. However, little information exists concerning seasonal photosynthesis and carbohydrate partitioning of leafy spurge, although such information would help to elucidate the involvement of sugar in controlling bud dormancy. An outdoor study was conducted over two growing seasons to determine and model seasonal patterns of photosynthesis and carbohydrate partitioning and their relationship to underground adventitious bud development and dormancy status. Photosynthesis and total nonstructural carbohydrate (TNC) content of aboveground tissues was greatest during vegetative growth. While photosynthesis gradually declined over the growing season, TNC decreased sharply during reproductive phase followed by a gradual decline between midsummer and autumn. Leaf starch increased dramatically to midsummer before declining sharply throughout late summer and early autumn; sucrose content responded inversely indicating a mobilization of starch reserves and export of sugars to root buds. Because newly formed underground adventitious buds showed a continuous increase in TNC from midsummer through autumn, export of sugars from aboveground tissues likely contributed to the increase in TNC. These results may facilitate strategies for biological control of leafy spurge. For instance, diverting photosynthetic assimilate away from early-season starch storage in leaves might disrupt the normal seasonal flow of sugars to underground vegetative buds in late summer/early autumn, thereby weakening bud dormancy and development and potentially disrupting the subsequent year¿s growth. Authors : Gesch, Russell, Palmquist, Debra, Anderson, James

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