Seasonal trends in the carbohydrates reserves of alfalfa

Abstract

A field trial was carried out at the Agriculture Experimental Station of the Federal University of Rio Grande do Sul, located in Guaíba, RS, Southern Brazil, to evaluate the seasonal (spring, summer and winter) changes in the total non structural carbohydrates (TNC) reserves in plant roots and crowns of three alfalfa (Medicago sativa L.) cultivars (Crioula, Hunter River and WL-518) and three progenies (1/7, 2/7 and 5/12) of the Crioula cultivar. Intensity or vigor of regrowth after cutting was evaluated also. In each season, a decrease in TNC reserves was observed: during spring and summer TNC content was reduced up to fourteen days after cutting, and 42 days in winter, recovering thereafter. The highest TNC level fluctuation occurred in spring, when forage yields were maximal. The highest TNC contents were obtained during spring and winter respectively, by cv. Crioula (29.6% and 25.8%), and progenies 1/7 (26.3% and 24.8%), 2/7 (27,1% and 23.1%) and 5/12 (25.7% and 28.0%). In each season, there was a significant (P<0,05) negative correlation between forage regrowth and TNC content. The productive and physiological performance of the 1/7, 2/7 and 5/12 progenies were similar to that of cv. Crioula, while the exotic cvs. Hunter River and WL-518 performed less satisfactorily.