Seed germination and growth of Eleucine indica and Euphorbia heterophylla as influenced by depth of planting and glyphosate

Abstract

Three experiments were conducted in a glasshouse and a laboratory to provide information on the effect of glyphosate (N-(phosphonomethyl) glycine) on, seed germination, seedling emergence and growth of goosegrass (Eleucine indica (L.) Gaertn) and wild poinsettia (Euphorbia heterophylla Linn), Glyphosate sprayed on top of potted soil did not affect the emergence of seeds planted 2 cm deep, However, glyphosate at 1.5 kg.ha^-1 stimulated the emergence of E. heterophylla seeds planted on the soil surface, Stimulatol)' effect of direct contact with glyphosate on germination of E. heterophylla seeds was confirmed in laboratory tests, The concentrations of glyphosate solutions that stimulated seed germination in E, heterophylla sown on filter paper in 9 cm petri-dishes were in the range 10- 30 ppm at quantities equivalent to 1.3-3.8 x 10^-1 kg a.i. ha^-l. The herbicide did not affect seed germination in E. indica. Glyphosate-treated seeds transferred to untreated soil emerged, Some of the emerged seedlings died eventually. Others had their growth adversely affected only 2 weeks after planting, At 4 weeks after planting, those seedlings which survived the adverse effect of the herbicide, in the first 2 weeks, were as vigorous as the control plants,