Allelopathic effect of aqueous extracts of common sunflower on seed germination and growth of field pea

Abstract

As climate changes, the development of new agroecological systems and the diversification of crop rotations open new opportunities for growing sunflowers in the northern regions of Europe. However, there is a lack of knowledge about the effect of sunflower grown in the Boreal region on other plants in crop rotation. This experiment was aimed to evaluate the allelopathic effect of aqueous extracts of different parts of the common sunflower ( Helianthus annuus L.) grown in the Boreal environmental zone on seed germination and growth of the field pea ( Pisum sativum L.). The following three factors were studied: factor A – two fertilisation levels of sunflower: unfertilised (N 0 P 0 K 0 ) and fertilised by N 80 P 60 K 90 ; factor B – three sunflower plants parts: leaves and stems (L+S), heads (H), and roots (R) for extract preparation; factor C – four concentrations (25%, 50%, and 75%) of sunflower aqueous extracts and deionised water (0%) as a control. All concentrations of sunflower extracts stimulated seed germination by 1.7– 6.7% at 4 days after sowing (4 DAS), compared to the control treatment. Extracts of heads and roots of sunflower had a significant ( p ≤ 0.05) inhibitory effect on pea root length and shoot length (7 DAS and 18 DAS, respectively). The roots extract contained the highest total polyphenolic content and total flavonoid content and had the greatest inhibitory effect on the fresh mass of roots and shoots. The data averaged across fertilisation level showed that 25% concentration of all sunflower parts extracts had a stimulatory effect, and extracts of 75% concentration had the highest inhibitory effect on root morphological parameters of pea. The results revealed that sunflower can be an allelopathic species causing a risk in a crop rotation. The suppressive effect of sunflowers on other plants including weeds can be applied in sustainable agriculture. Therefore, the detailed studies are necessary for further reveal of the allelopathic effect of sunflower grown in the Boreal environmental zone not only on peas but also on other target crops.