Effect of temperature and photoperiod on growth and reproductive development of goatsrue

Abstract

Goatsrue (Galega officinalis L.) was introduced into northern Utah from Europe as a potential forage crop in 1891. Subsequent testing indicated goatsrue was unpalatable and toxic to livestock. The test plots were abandoned, and goatsrue escaped to become established as a weed. Goatsrue now is targeted for eradication under the Federal Noxious Weed Act, and information about its environmental requirements and potential for further range expansion in the United States is needed. In controlled environment chambers, plants were grown for 89 days in 4 day/night temperature regimes. Goatsrue produced 88, 100, 57, and 86% of its maximum dry matter at 26/14, 26/22, 34/14, and 34/22 degrees C, respectively. Dry matter production was closely correlated with leaf area duration. When 20-day-old plants were transferred from a 12-hour photoperiod to longer photoperiods, flower buds appeared after 20, 26, and 69 days in photoperiods of 18, 16, and 14 hours, respectively. Plants in these longer photoperiods subsequently flowered and produced fruit, but no reproductive development occurred after 130 days in the 12-hour photoperiod. Goatsrue is not well-adapted to the large diurnal variation in temperature typical of summer conditions in the Intermountain region of the United States. Temperature conditions in the Midwest or South would be more favorable to its growth.