Variability of Miserotoxin Concentration in Timber Milkvetch

Abstract

The variability in miserotoxin concentration of 120 individual timber milkvetch plants was determined in the bud, flower, and pod stages of growth on rough fescue grassland, parkland, and Douglasfir zone locations. Although a broad dispersion in miserotoxin levels was evident within each sampling unit of ten plants, the grassland samples exhibited the greatest toxicity with an exceptional level (10.17 +/- 1.13%) occurring during the bud stage. The bud stage of the parkland samples yielded intermediate concentrations (5.22 +/- 1.18%) while forest plants contained lower miserotoxin levels (4.08 +/- 0.95% to 2.49 +/- 0.47%). A decline in miserotoxin levels occurred during the bud-to-pod interval at the grassland and parkland sites, but significant differences were not apparent between the progressive stages of growth at the forest locations. The timber milkvetch toxicity patterns based on the variability of individual plants confirmed previously described trends derived from composite sampling.