ALFALFA FOOD RESERVES ESTIMATED CHEMICALLY AND BY ETIOLATED GROWTH

Abstract

A 3-yr field study was conducted to compare two common methods of estimating stored food reserves in crowns and roots of alfalfa (Medicago sativa L.) during autumn and winter. A chemical method to measure total nonstructural carbohydrates (TNC) was compared with a method that measured total etiolated growth (TEG). No significant correlation was observed between the two methods. TNC increased during autumn, attained a maximum in midwinter and then declined in the spring in association with rising soil temperatures. In contrast, TEG attained a maximum in the fall and declined or remained at a steady level throughout the winter and during rapid growth in the spring. This suggests that not all TNCs in crowns and roots are used for growth of shoots. A significant and approximately constant level of TNC remained in the crowns and roots following completion of etiolated growth. Cutting frequency and cultivars significantly affected TEG and TNC values, but the specific information provided by each measurement remains to be elucidated.Key words: Alfalfa, food reserves, TNC, etiolated growth, clipping, crown buds