Allelopathic effect of aqueous extracts of different organs of three sunflower cultivars on germination of radish

Abstract

This study aimed to evaluate the allelopathic potential of aqueous extracts of different organs of three sunflower cultivars on the germination and initial development of radish. The study was conducted in a Laboratory of Plant Physiology of the Federal University of Santa Maria, Brazil. The design was completely randomized in a threefactor scheme with four replications. The first factor consisted of three sunflower cultivars: Olisun 3, Olisun 5, and Aguará 6. The second factor consisted of different organs: leaves, stems, and roots. The third factor consisted of the extracts concentrations: 0, 25, 50, 75, and 100%. The experimental unit (EU) used was gearboxes with two sheets of germitest paper that were moistened with the extracts. The EUs were placed in BOD germination chamber at 25 °C. Daily count of germinated seeds was performed. The radicle length and hypocotyl were measured on the 10 th day. The variables analyzed included germination (G); germination speed index (GSI); radicle length (RL); and hypocotyl length (HL). Sunflowers have allelopathic potential on the radish. The extract concentration of 75% of all organs and cultivars were sufficient to significantly reduce the variables. The allelopathic activity differs between organs (leaves, stems, and roots) and sunflower cultivars. The amount of allelopathic effects vary in the order of root, stem, and then leaf. Extracts from the roots showed the greatest allelopathic effect on germination and initial development on the radish; however, this depends on the cultivar used. Field studies should be performed to verify such allelopathic activities.

The Allelopathic Activity of Aqueous Extracts of Helianthus annuus L., Grown in Boreal Conditions, on Germination, Development, and Physiological Indices of Pisum sativum L.

“…In comparison with L+S extract, the highest stimulating effect on SG had H and R extracts from both UDP and FDP. Our experimental findings are in line with previous results [12,16,18], which indicate differences of the allelopathic effect among plant parts. These results are contrary to the study of Bashir et al [11], wherein sunflower organ extracts inhibited wheat SG.…”

“…H extract showed the highest promotion effect on these indices. Our experiment corroborates with previous results [12,16,20], in which it was found that allelopathic potential of sunflower parts vary from each other. Kandhro et al [25] reported that shoot of sunflower was found more allelopathic than root.…”

“…Our findings are in line with previous results [18,42], indicating that with the increase in concentration, the dry weights of rice, mung bean and chickpea were progressively reduced, compared to the control. Allelopathic compounds suppress water and nutrients uptake by roots, reducing photosynthesis and biomass accumulation [12,22]. The application of water extracts of sunflower reduced the weed dry weight (10-62.0%) compared to the control [48].…”

“…Most of allelochemicals are secondary plant metabolites, belonging to terpenoids, phenolic compounds, long chain fatty acids, organic cyanides, alkaloids, and others [8,9]. Allelopathic substances obtained by above-ground plant parts decomposing in soil could potentially influence a seedling's growth [10][11][12][13], accumulation of dry mass [14,15] and photosynthesis [16][17][18].…”

“…The most common laboratory bioassays for phytotoxic compounds are seed germination and growth experiments. If a sensitive test plant is exposed to allelopathic compounds, its seed germination and seedling growth are reduced [12,25].…”