Effects of Allium species plant extracts and their active ingredients on inhibition of plant growth

Abstract

The purpose of this study was to investigate what additional uses can be made of Allium species’ various extracts, particularly their inhibitory effects on plant growth. In addition to their extracts, we also studied the inhibitory effects of Allium active ingredients. The inhibition of cucumber and barley shoot and root lengths was greatest when water, boiled water and ethanol extracts of garlic flesh were used. In studies using cucumber, shoot and root lengths were 49–63% inhibited when treated with boiled water extracts of garlic flesh at a 5% concentration. In studies using barley and the same application, shoot and root lengths were 70–77% inhibited. Regardless of extraction method, garlic stem, peel and root extracts were less effective at growth inhibition. In order to investigate the inhibition rates of other Allium plants, we used boiled water extracts of onion flesh, welsh onion root, and garlic root of various cultivars. The garlic flesh extracts produced higher inhibition rates than onion flesh and welsh onion root extracts. Cucumber and barley growth were 81–100% inhibited in studies using garlic extracts of four cultivars (Deaseo, Haenam, Seosan and Namdo) at 3 and 5% concentrations. Additionally, weeds Quamoclit coccinea, Digitaria ciliaris, Echinochloa oryzoides and Digitaria ciliaris were, with few exceptions, 61–100% inhibited in studies using garlic extracts of Heanam and Seosan cultivars at 5% concentrations. Both total phenol and total flavonoid contents were higher in onion cultivars than in garlic cultivars. However, plant growth inhibition was higher in garlic extracts than onion extracts. Thus, the growth inhibition rates may not be related to only phenolic or flavonoid contents. An active ingredient compound ally disulfide was more effective in inhibiting plant growth than the quercetin and ascorbic acid. Although extracts from Allium species were shown to effectively inhibit growth, further studies are needed to determine whether a single active ingredient or mix of active ingredients cause growth inhibition.