Carbohydrate Reserves in Roots of Dalmatian Toadflax

Abstract

Reserve carbohydrates of Dalmatian toadflax (Linaria dalmatica(L.) Mill.) in eastern Washington were at their highest levels in autumn at the end of the growing season, and the lowest point occurred at the beginning of flowering about June 15. A one-time removal of first-year floral stems (June 11, 1964) did not significantly lower reserve carbohydrates when measured in September, but similar clipping of floral stems the second year (June 16, 1965) did cause a significant reduction. Reserves were reduced by 2-(2,4,5-trichlorophenoxy)propionic acid (silvex) at 1.12 or 1.68 kg/ha but were not reduced by 4-amino-3,5,6-trichloropicolinic acid (picloram) at the same rates. Combinations of equal weights of the two herbicides to total 1.12 or 1.68 kg/ha caused a significant reduction in reserve carbohydrates. The combinations of silvex and picloram appeared to have an additive toxic effect, but the reduction of reserve carbohydrates was no greater than that caused by silvex alone at 1.12 or 1.68 kg/ha. Lethal action of the herbicides did not appear to be caused by reserve carbohydrate depletion. Glucose and fructose were the major reducing sugars detected in chromatographic analysis.