Seasonal changes in carbohydrate levels in tissues of Carex lacustris

Abstract

Seasonal changes in total nonstructural carbohydrates (TNC) levels in aboveground and belowground tissues of Carex lacustris were determined. TNC concentrations of aboveground tissues averaged 15–20% of the dry weight throughout the year, ranging from 31.3% in newly emerged shoots in September to 3.1% in mostly dead shoots in December. Belowground, TNC concentrations ranged from a low of 16.4% in young rhizomes in midsummer to a high of 44.9% in late October.TNC content of shoots was 68.5 g/m2 on May 5, increasing to a peak of 224.5 g/m2on August 5. Levels declined to a low of 31.6 g/m2 by December 5, of which 74% was found in young shoots about to overwinter. Belowground TNC was 107.5 g/m2 on May 8, declined somewhat into June, then increased to a maximum of 240 g/m2 on October 24. The data indicate these belowground reserves are important for the species to overwinter successfully.The difference between the minimum TNC content of the sedge biomass in late May and the peak in October represented a gain over the summer of approximately 205 g/m2.