Selective and toxic effect of an alkaloidal extract from Rhazya stricta against some plants

Abstract

The crude alkaloidal extract isolated from Rhazya stricta Decne (Apocyanaceae) was tested for its effects on the seedling development of two dicot plants (alfalfa, Medicago sativa and wild radish, Raphanus sativus), and two monocot plants (Italian ryegrass, Lolium multiflorum, and wheat, Triticum aestivum) by adding the aqueous 100, 150, 200, 300, and 400 ppm solutions to the seeds of these plants on filter papers in petri dishes at 25 ±1oC. The dicot plants were more sensitive to the extract than the monocot plants, root growth was more sensitive than shoot growth in all tested plants. Moreover, Italian ryegrass was more sensitive to the extract than wheat. The I50 values (the concentration required to inhibit 50 % of the growth) for the root growth of the four mentioned plants were 158, 180, 222, and 477 ppm, respectively. The I50 values for the shoot growth of the tested plants were 409, 558, 379, and > 1000 ppm, respectively. The selective and toxic effects of this extract may be exploited in many ways.