Effects of Minthostachys mollis essential oil and volatiles on seedlings of lettuce, tomato, cucumbre and Bidens pilosa. (Alonso Amelot, Miguel; Usubillaga, Alfredo; Avila Nuñez, Jorge Luis; Oliveros Bastidas, Alberto y Avendaño Meza, Mairsabel) Abstract The extraction and chemical composition of essential oil of Minthostachys mollis (Kunth) Griseb (Lamiaceae) and its inhibitory effects on germation and shoot/root elongation of lettuce, tomato, cucumber and Bidens pilosa (L.) var pilosa described. Hydrodistillation gave 2.9% (v/w) of essential oil (97.8% of terpenoids). Pulegone (83.6%), menthone (7.6%), limonene (2.0%) linaloo (1.2%), and isomenthone (0.8%) were the major components of essential oil. This oil was applied at 1.0, 2.5 and 5.0 ul on filter paper disks for bioassay. The seed germination of all test spp was completely inhibited even with the lowest dose. Five days-old transplants of seedlings (7 days for B. pilosa) exposed to 5, 10 and 20 ppm of oil in the vapour phase inhibited the elongation of shoot more than root and its inhibitions was concentration dependent B. pilosa was inhibited at 20 ppm with necrosis of hypocotyls.alonso@ula.veusubilla@ula.ve, usubillaga@cantv.netjlavila@ula.vealoliver@ula.vemaribea@ula.veNivel monográfico