title: Light-induced starch degradation in non-dormant turions of Spirodela polyrhiza.
abstract: Continuous red light controls starch degradation in turions of Spirodela polyrhiza [Dölger, K., U. K. Tirlapur and K.-J. Appenroth [1997] Photochem. Photobiol. 66, 126-127 (1997)]. This light could be replaced by repeated red light pulses with the reciprocity law fulfilled over a large range of fluence rates. The effect of red light pulses repeated every 24 or 12 h for 6 days was reversible by subsequent far-red light pulses. In contrast, hourly applied red pulses were irreversible by far-red light. This discrepancy was explained by showing the starch degradation activity of far-red pulses themselves. The investigated process was categorized as a phytochrome low fluence response with an unusual property: requirement of light treatment for several days. A partial fulfillment of this requirement was obtained with a red pulse followed by a dark period and a 24 h continuous irradiation. These results suggest the existence of two separate steps in the process of starch degradation in turions: formation of a sprout (= sink) during the pulse-induced germination, and starch degradation in the storage tissue (= source) induced by the second light treatment.
authors.affiliation: Universität Jena, Institut für Allgemeine Botanik, Lehrstuhl Pflanzenphysiologie, Dornburger Strasse 159, D-07743 Jena, Germany. klaus.appenroth@uni-jena.de
authors.forename: K J
authors.initials: KJ
authors.lastname: Appenroth
authors.forename: H
authors.initials: H
authors.lastname: Gabrys
mesh_terms: D008027:Light; D019684:Magnoliopsida / Q000378:metabolism* / Q000528:radiation effects*; D010834:Phytochrome / Q000378:metabolism; D013213:Starch / Q000378:metabolism*
chemical_list: D010834:Phytochrome; D013213:Starch