Allelopathic effects of Oldeania alpina (K. Schum.) Stapleton leaf aqueous extract on seed germination and initial seedling growth of two selected crops

Empirical evidence indicates that allelopathic chemicals produced by perennials plants result in a positive or negative change in the germination, growth, and behaviour of other plants growing in close association. This study aimed to investigate the allelopathic effects of Oldeania alpina leaf aqueous extract on germination and initial growth of barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) test crops under laboratory conditions. Four different solvents (i.e., hexane, ethyl acetate, methanol, and water) were used to prepare O. alpina leaf extracts. Then, the extracts were subjected to qualitative analysis to identify the presence of allelochemical compounds namely; flavonoids, phenols, tannins, terpenoids, steroids, quinones, coumarins, saponins, and, anthraquinones. Aqueous extract concentrations (i.e., 0 %, 2.5 %, 5 %, 7.5 %, and 10 %) were used to irrigate seeds of test crops using a completely randomized design. The analysis revealed that better germination percentage, speed, and time for both wheat and barley were observed at control while reduced as the concentration of the extract increased up to 10 %. Higher mean shoot growth for wheat (105.2 ± 14.6 mm) and for barley (94.3 ± 30.9 mm) were obtained for the control treatment. A similar trend was observed for root lengths of wheat (104.0 ± 12.4 mm) and barley (65.9 ± 18.4 mm). The mean values decreased for each of the studied parameters as the concentration of the extract increased. Except for anthraquinones, all tested allelochemicals in extracts inhibited germination and initial growth of barley and wheat crops. This implies that planting wheat and barley close to O. alpina may require field-level investigation.