# Alleploatible Potential of Sunflower Genotypes at Different Growth Stages on Lettuce
## 4 Discussion  
Results of the experiment showed that sunflower water extracts possess significant allebotathic potential for lettuce germination and growth, thereby confirming similar findings in previous studies. Laboratory bioassays confirmed sunflower leaf water extract in 10% concentration significantly delayed and reduced mustard and oilseed rape germination but promoted seedlings' dry weight [23]. Greenhouse experiments showed that incorporated sunflower residues significantly delayed and inhibited germination of jungle rice (_Echinochloa colona_) by 22.5% [31], while sunflower leaf extract in combination with herbicide pretilachlor reduced germination of barnyard grass (_E. crus-galli_) [35]. Crop density, weight of seed/grain and total yield of guar (_Cyamopsis tetragonoloba_), maize (_Zea mays_), sorghum (_Sorghum vulgare_) and pearl millet (_Pennisetum americanum_) were significantly reduced in fields with sunflower residues [37]. When comparing the response of seedlings to the effect of extracts, germination was the least affected, followed by shoot length and fresh weight, while the greatest negative potential was observed for root length. [PERSON] et al. [38] also concluded that root elongation of maize, soybean (_Glycine max_) and wheat (_Triticum aestivum_) seedlings were more sensitive to the effect of extracts compared to seed germination. The presence of sunflower water extracts caused morphological abnormalities in seedlings in the form of root thickening with brown colour [33]. Besides germination and growth, the application of sunflower extracts affects the contents of gibberellic (GA), indole-3-acetic (IAA) and abscisic (ABA) acids in leaves and roots, as well as proline, chlorophyll, sugar, protein, superoxide dismutase (SOD) and peroxidase (POD) contents in leaves of wheat [32]. Various allebotathic compounds, such as phenolics (syringic, vanillic, sinapic and \(p\)-coumaric acids) and sesquiterpene lactones, have been identified in sunflower residues and leaves [12; 39]. Negative allebotathic potential significantly increased with the increase of sunflower water extracts concentration, which was especially pronounced in the growth of seedlings. Higher concentrations usually have a greater detrimental effect, and studies sometimes report germination and growth inhibition up to 100% [19; 22; 38; 40]. On the contrary, positive effects can occur with extracts in lower concentrations promoting seedlings' growth and accumulation of biomass [14; 23], which in our study was recorded with Genotypes 1 and 2. Such extracts could be used as biostimulators for crop growth promotion [13]. [PERSON] et al. [40] stated that, in addition to the stimulative effect on crops, ideal extracts should simultaneously have herbicidal activity on weeds. This emphasizes the need for assessing allebotathic potential on both weeds and crops as test species. The results of this experiment indicated that although all genotypes showed a certain degree of allebotathic activity, depending on both growth stage and extract concentration, several genotypes proved to possess greater overall inhibitory potential. Among these were Genotypes 4 and 7, which were hybrids, and Genotypes 5 and 8, which were used as their maternal lines. The reduction of seedlings' root length and fresh weight amounted to 80.6% and 38.1%, respectively. [PERSON] et al. [12] demonstrated significant differences among eight sunflower genotypes in their suppressive abilities towards weeds by root exudation and residue incorporation. They marked a higher total content of phenolic compounds in genotypes with high inhibitory potential. Using the relay seeding method, [PERSON] et al. [34] studied 23 sunflower genotypes in order to evaluate the allebotathic potential of root exudates against the weed species _Bidens pilosa_. Great variability among genotypes was observed, and although the decline in _B.