Phytotoxic effects of aqueous extracts of apple of sodom (Calotropis procera W.T) on seed germination of Ischaemum afrum (J.F.Gmel.) dandy using probit analysis

Abstract

This study was carried out to investigate the phytotoxic effects of aqueous extracts of leaves, inflorescences, stems and roots of apple of Sodom (Calotropis procera W.T) on seed germination of Ischaemum afrum using probit analysis. Laboratory experiments were carried out at the Faculty of Agricultural Sciences, University of Gezira, Sudan in season 2014/15. Ten concentrations of the aqueous extract of each part of apple of Sodom were prepared by sequential dilution of the stock extract (50g/l) with sterilized-distilled water to give 2.11, 4.21, 6.34, 8.42, 10.53, 12.63, 14.13, 16.84, 18.94 and 21.05 g/l. A control with sterilized-distilled water was included for comparison. Treatments were arranged in completely randomized design with four replicates. The seeds were examined for inhibition (%) in germination at three days after initial germination. Data were subjected to probit analysis procedure (P 0.5).The results showed that the aqueous extracts of all tested parts of apple of Sodom suppressed seed germination of the I. afrum and there was direct positive relationship between concentration (g/l) and inhibition (%). The result also revealed that the leaves aqueous extract of apple of Sodom was more toxic (LD₅₀ = 6.3 g/l) to the seeds of I. afrum followed by aqueous extract of inflorescences (LD₅₀ = 7.2 g/l), stems (LD₅₀ = 11.4 g/l) and roots (LD₅₀ = 12.7 g/l). The results indicated that the aqueous extracts  of apple of Sodom had toxic effect to the seeds of the I. afrum and could offer potential for the development of alternative herbicides.

Keywords: Allelopathy; Apple of Sodom; Calotropis; Ischaemum; Phytotoxic; Probit