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

Evaluation of the allelopathy relationship between different crops is a sensible strategy fallowing the correct use of positive effects and to avoid the disadvantageous effects among plants. This study aimed to detect the allelopathic effect of aqueous extracts of sunflower (Helianthus annuus L.), grown in a boreal climatic zone, on the growth, subsequent development, and physiological traits of pea (Pisum sativum L.). Three factors have been studied: donor plant fertilization (unfertilized and fertilized), aqueous extracts from donor plant organs (leaves and stems (L+S), heads (H) and roots (R)); four concentrations of extracts (0%, 25%, 50% and 75%). The aqueous extracts from fertilized sunflower donor plant at 25% and 50% concentration acted as potential biostimulants that stimulated pea seed germination (SG), whereas L+S and R extracts at 75% concentration from unfertilized donor plant inhibited SG, at 4 days after sowing. The aqueous extracts demonstrated a stimulating effect on above-ground and root dry mass, compared to the control. The concentration of extracts demonstrated a significant inhibitory effect on SPAD. R extract revealed the strongest allelopathic effect on physiological traits of pea. L+S and H extracts at 25% concentration had stimulating effects, while 50% and 75% concentrations showed inhibiting effects on the photosynthetic rate. The water use efficiency, stomatal conductance, and stomatal limitation were inhibited, whereas, the transpiration rate, photosynthetic water use efficiency and intercellular CO2 concentration were stimulated, with an increasing of extract concentrations, comparatively to the control.

Automated summary

Evaluating the allelopathy relationship between different crops is important for understanding the interaction between plants and utilizing their positive effects while avoiding negative effects. In this study, the allelopathic effect of sunflower extracts on pea growth and physiological traits was investigated. The results showed that fertilized sunflower extracts at 25% and 50% concentrations acted as biostimulants and stimulated pea seed germination, while unfertilized extracts at 75% concentration inhibited seed germination. The extracts also had effects on above-ground and root dry mass, photosynthetic rate, and physiological traits of pea. The allelopathic effect was stronger with root extracts and higher concentrations. An increasing concentration of extracts also affected water use efficiency and stomatal conductance of pea plants.