In vitro evaluation of low dosages of 2, 4-D on germination and seedling growth of wheat and associated weeds

Abstract

Hormesis is a biphasic dose response to an environmental agent characterized by low dose stimulation and high dose inhibitory or toxic effect. In order to develop an effective weed management system, the stimulatory and/or inhibitory response of low doses of herbicides on germination and growth of weeds should be considered. Thus, a laboratory study was conducted to test the effect of low dosages of 2,4-D on wheat (Triticum aestivum L.) and associated dicotyledonous weeds. Low dosages of 2,4-D (0, 5, 10, 20, 40 and 50 g/ha) failed to accelerate either seed germination or seedling growth of T. aestivum and tested four weed species -Phalaris minor Retz., Avena ludoviciana Durieu., Medicago denticulata Willd. and Rumex dentatus L. under in vitro conditions in Petri-dishes. The application of 2,4-D inhibited the seed germination and seedling growth of these weeds in a dose dependent manner with higher concentrations being more inhibitory. The sodium formulation of 2,4-D more adversely affected the germination of P. minor and A. ludoviciana as compared to its ethyl ester formulation. The results indicated that 2,4-D when used as a post-emergence herbicide in wheat fields can delay the emergence of new flushes of weeds like P. minor, A. ludoviciana, M. denticulata and R. dentatus due to its inhibitory effect on their germination. It could be concluded that low doses of 2,4-D did not enhance germination/seedling growth of wheat and associated weeds.