Germination of locoweed seed (astragalus mollissimus torr) at different temperatures ranges and water stress levels

Abstract

Locoweed (Astragalus mollisssimus Torr.) is one of the most important toxic plants found in the Chihuahuan desert rangelands. Because its population is highly irregular, it is important to develop control as well as ecological studies. The objective of this work was to estimate the effect of temperature and water stress levels on locoweed seed germination. Seed was collected during 1992 in the central part of Chihuahua. Germination tests were conducted using six temperatures and five moisture levels. No interaction was detected between temperature and moisture levels (P<0.05). Highest germination (P<0.05), 75, 70, and 75 %, was obtained at the temperature ranges of 15 to 25, 15 to 30, and 20 to 30 .C, respectively. The highest germination (P<0.05) was 76, 69, and 70 % at 0, -0.3 and -0.5 MPa, respectively. Germination at the highest water stress level, -0.9 Mpa, was 47 %, and for extreme temperatures, 10 to 20 and 20 to 35 .C was 29 and 23 % respectively. These results point out that locoweed can germinate throughout the Summer and Autumn, even with low soil moisture.