Change in Carbohydrates in Alfalfa (Medicago sativa L.) Roots During the Period of Floral Initiation and Seed Development1

Abstract

Alfalfa plants grown under field conditions at Tucson, Arizona, were used to investigate the change in acidhydrolyzable carbohydrates, glucose, fructose, sucrose, and starch stored in the roots during the time of floral initiation and seed development at three different seasons of the year.Acid‐hydrolyzable carbohydrates and starch reached their lowest level in the roots more rapidly in plants that were cut in June and August as compared with plants that were cut in April to begin growth for seed production. Floral initiation and development also occurred earlier during the June and August growth periods. This early reduction in stored reserves coincided with early floral initiation and development. The concentration of glucose, fructose, and sucrose was quite low in alfalfa roots during all growth periods. Positive and significant association existed between the concentration of specific carbohydrate fractions in alfalfa roots during the first three weeks after forage removal and seed production, number of pods per stem, number of seeds per pod, and percentage pod set.