A study of the phytotoxic effects of the aerial parts of Senecio westermanii Dusén (Asteraceae) on Lactuca sativa L. and Allium cepa L. seeds

Abstract

The objective of this study was to evaluate the effects of the ethanolic crude extracts and fractions of the species Senecio westermanii Dusén on Lactuca sativa L. (lettuce) and Allium cepa L. (onion) seeds. We assessed the germination, growth, root respiration and photosynthesis of the target species in Petri dishes (9.0 cm diameter) containing filter paper n°6. The study was conducted using 50 seeds per plate and held in 4 replicates per concentration of each sample. In the germination there was an inhibitory effect of fractions hexane (FH) and chloroform (FCl) at concentrations of 500 and 1000 µg/mL. There was a reduction in the radicle growth of lettuce by 14 to 24% and a reduction of hypocotilum by 14 to 28%. As for the radicle of the onion was up 74% reduction to the FCl and the coleoptile was 24 and 45% reduction for FH and FCl, respectively. Inhibitory effects in the root respiration of lettuce were detected in all the samples analyzed, with results ranging from 16 to 83%. For the seeds of A. cepa, there was an encouragement for the FCl and ethyl acetate fractions (FAE), with results ranging from 94 to 142% and 76 to 150%, respectively. With regard to the photosynthesis of L. sativa, there was no significant difference between the control, and as for the A. cepa, there was a strain in inhibition concentrations of 250 and 500 µg/mL, which ranged from 27 to 68%. The samples of S. westermanii caused changes in the target species and thus can be used as a natural herbicide.

Phytotoxic and Enzymatic Study of Philodendron meridionale on seeds of Lactuca sativa L.

“…A similar procedure was also performed using methanol (solvent control) and water (negative control). The experiment was conducted in quadruplicate, and the gerbox with L. sativa seeds were incubated in a germination chamber (Bio-Oxygen Demand incubator), with a relative humidity of ~80% and constant temperature of 25C (Brasil, 2009;Krause et al, 2015;Merino et al, 2018; Gatto et al, 2020).…”

“…Seeds were considered to have germinated when the radical appeared to protrude through the tegument, and germination was measured in terms of rate (speed and percentage; (Laboriau, 1983) and germination velocity index (GVI; Maguire, 1962). The GVI was calculated for each replicate, according to the following equation: GVI: G1/N1 + G2/N2 + Gn/Nn, where GVI represents the germination speed index.G1, G2, ..., Gn represent the number of seeds that germinated on each day, and N1, N2, ..., Nn represent the number of days from sowing until the seventh day, using the sum of the germinated seed quantity ratio and the day of germination (Krause et al, 2015;Merino et al, 2018).…”

“…On the last day of the germination test (i.e., 7th day), the hypocotyl and radical lengths were measured using a pachymeter, and to measure dry mass, the seedlings were dried in an oven at 60°C until reaching a constant weight (Macias et al, 2000;Merino et al, 2018)…”

“…Root respiration capacity was measured according to Steponkus and Lanphear (1967); Krause et al (2015) and Merino et al (2018). Briefly, 1.0 cm pieces were cut from the ends of 10 roots and transferred into test tubes with 5 mL 0.6% (m/v) triphenyl tetrazolium hydrochloride and 1 mL sodium phosphate (mono and dibasic) buffer (0.05 mol.L -1 pH 7.0).…”