Response of Alfalfa (Medicago spp.) to Light Interruption of the Dark Period¹

Abstract

The influence of light interruption of the dark period on flowering and certain growth characteristics of alfalfa (Medicago spp.) was studied under field conditions at Tucson, Ariz.One light interruption of 30 min in the middle of the dark period caused significant differences in flowering percentage, height, and dry‐weight production of specific cultivars. Alfalfa plants that were grown under light interruption had smaller crowns, flowered earlier and more profusely, and produced less dry matter compared to plants grown under natural daylength.Seasonal temperatures influenced the effects of light interruption of the dark period. Differences between light treatments with respect to flowering were most evident during shorter natural daylengths which coincided with the cooler growth periods, while differences in production of dry matter were most evident when maximum and minimum temperatures were highest.Light interruption of the dark period can be used to obtain more rapid and complete flowering of alfalfa under field conditions.