Allelopathy Journal

We examined the effect of husk extracts of wild rice spp. on root and shoot growth of lettuce, barnyard grass and Eclipta thermalis (false daisy). The inhibition was generally greater in root growth than in shoot growth. The husk extracts at 50 g eq./l of all tested wild rice spp. caused strong inhibition in root growth of barnyard grass. The husk extracts at 50 g eq./l of O. glumaepatula caused the greatest inhibition in root growth of lettuce, but the greatest promotion in shoot growth of false daisy, followed by O. barthii, O. rufipogon, and O. meridionalis. Thus, the husk extracts of O. glumaepatula contain allelochemicals that inhibit root growth of lettuce and barnyard grass, but promote shoot growth of false daisy. To characterize these allelochemicals in O. glumaepatula husk, its husk extracts were partitioned between water and ethyl acetate layers. The lettuce root growth inhibition was greater in water layer of O. glumaepatula husk extracts than in ethyl acetate layer. However, the inhibition in root growth of barnyard grass was greater in ethyl acetate layer than in water layer. The false daisy shoot growth promotion was greater in water layer of O. glumaepatula husk extracts than in ethyl acetate layer. These results suggest that the husk extracts of O. glumaepatula contain water soluble allelochemicals that inhibit root growth of lettuce but promote shoot growth of false daisy and ethyl acetate soluble allelochemicals that inhibit root growth of barnyard grass.