Efeito alelopático do extrato aquoso de cravo de defunto (Tagetes erecta) sobre nabo forrageiro, corda de viola e soja

Abstract

Allelopathy refers to the beneficial or harmful influence that one plant organism can have on another, through chemical compounds released into the environment, which allows an alternative method for controlling weeds. The objective of this work was to verify the allelopathic potential of marigold (Tagetes erecta), as well as to evaluate its effect on forage turnip, viola string and soybeans. For the analysis, 150 g of aerial part, 150 g of root and 75 g of each part were weighed to make up the entire plant, being cut into small fragments of 0.5 – 2.0 cm, and placed in 2,000 mL of water distilled, resting for 48 hours, with exposure to light only during the day, in order to obtain the aqueous extract, in addition to the control treatment, only with distilled water. The experiment was conducted in the Plant Health laboratory at UTFPR – DV, with 4 replications for each treatment, with 36 seeds of forage turnip and viola string distributed in gerbox-type boxes, and 4 replications of 50 seeds arranged on a paper roll for soybeans, all on germitest paper. The samples were taken to a germinator at a controlled temperature of 25°C for seven days. Assessments took place daily after radicle protrusion. The variables analyzed were percentage of germination (%G), germination speed index (IVG), average germination speed (VMG), average germination time (TMG), shoot length (CPA) and root length (CR), shoot dry matter (MSPA), root dry matter (MSR). The experimental design was completely randomized, with means compared using the Tukey test at 5% probability. There was a negative influence of the extract on the germination percentage of viola string, whereas for forage turnip, an increase in TMG and a reduction in VMG were observed when subjected to aerial part extract. None of the extracts interfered with CPA, CR, MSPA and MSR for seedlings, turnip and soybeans, but significantly reduced the MSR of viola string. It is concluded that the marigold extract can cause positive or negative allelopathic interference on the tested species.