Growth of white clover seedlings treated with aqueous extracts of leaf and root of tough lovegrass

Abstract

-This study was carried out to investigate the effect of extracts of leaf and roots of tough lovegrass (Eragrostis plana) on seedling growth of white clover (Trifolium repens), in two experiments. The first experiment was conducted as a pilot test, in which two concentrations (30 and 60%) of leaf aqueous extract were tested. In Experiment II, source (leaf/root) and concentration (5 and 10%) of the extracts were combined. Distilled water was used as control in both trials. Fifty seedlings at 7 days of age were placed in gerbox containers on filter paper moistened with extracts and incubated at 25°C for 14 days. In the first experiment, percentage of normal seedlings decreased by 82.5% and 100% at the concentrations of 30% and 60%, respectively, which indicated the need to increase the dilution of the extracts. In the subsequent experiment, the extracts from the two sources, at 10% of concentration, reduced by 78% the percentage of normal seedling and increased the percentage of abnormal seedlings, which reached 27%. At 5% concentration, the leaf extract was the most deleterious treatment, resulting in greater mortality (M=27.6%) and abnormality (A=19.5%) of seedlings, compared to the root extract (M=4.8%; A=9.5%) and the control (M=2.4%; A=0.25%). The morphological changes caused by the extracts were radicle necrosis, retention of cotyledons and absence of secondary roots. The results suggest that allelopathic compounds from leaves and roots of tough lovegrass differ in chemical nature and/or concentration.Key Words: allelophaty, abnormal seedlings, dead seedlings Crescimento de plântulas de trevo-branco tratadas com extratos aquosos de folha e raiz de capim-annoni-2 RESUMO -Este estudo foi realizado para investigar o efeito do extrato de folhas e raízes de capim-annoni-2 (Eragrostis plana) no crescimento de plântulas de trevo-branco (Trifolium repens), em dois experimentos. O primeiro experimento foi conduzido como teste-piloto, no qual foram testadas duas concentrações (30% e 60%) de extrato aquoso de folhas. No experimento II houve uma combinação de fonte (folhas e raízes) e concentração (5% e 10%) dos extratos. Água destilada foi utilizada como testemunha em ambos os ensaios. Cinqüenta plântulas com sete dias de idade foram colocadas em caixas gerbox, sobre papel-filtro umedecido com os extratos, e incubadas a 25ºC durante 14 dias. No primeiro experimento, o percentual de plântulas normais decresceu em 82,5% e 100% nas concentrações de 30% e 60%, respectivamente, o que indicou a necessidade de se aumentar a diluição dos extratos. No experimento subseqüente, os extratos das duas origens, a 10% de concentração, reduziram em 78% o percentual de plântulas normais e aumentaram o percentual de plântulas anormais, que atingiu 27%. A 5% o extrato de folha foi o tratamento mais deletério, resultando em maior mortalidade (M=27,6%) e anormalidade (A=19,5%) de plântulas, comparado ao de raiz (M=4,8%; A=9,5%) e à testemunha (M=2,4%; A=0,25%). As alterações morfológicas causadas pelos extratos foram necrose da rad...

Allelopathy and Allelochemicals of Eragrostis plana (Poaceae) and its Relation with Phenology and Nitrogen Fertilization

“…At the vegetative stage, probably because the time between the applications of N and the harvest was the shortest, there was no difference 5 among doses. In the tough lovegrass that was not fertilized with N, Alfaya et al (2002) The allelopathic effect of the aqueous extracts on lettuce was visually observed (Figure 3) and quantified according to the germinability and the GSI (Table 2), in accordance with other authors who evaluated the allelopathic potential of the tough lovegrass (Ferreira et al, 2008;Favaretto et al, 2011). The allelopathic symptoms, in a greater or a lesser degree and depending of the extract, included necrosis, shortening and winding of the root apex (Figure 3), which is commonly reported in bioassays of this type (Souza Filho et al, 1997).…”

“…The allelopathic symptoms, in a greater or a lesser degree and depending of the extract, included necrosis, shortening and winding of the root apex (Figure 3), which is commonly reported in bioassays of this type (Souza Filho et al, 1997). These symptoms were observed in white clover seedlings (Trifolium repens, Fabaceae) that were subjected to leaf and root extracts of the tough lovegrass (Favaretto et al, 2011).…”

“…The success of this species in colonizing extensive rural and ruderal areas is attributed, in part, to its allelopathic action (Ferreira et al, 2008;Favaretto et al, 2011). Recent studies have indicated the presence of phenolic compounds in the roots and leaves of this grass (Favaretto et al, 2015).…”

AUTOTOXICITY IN TOUGH LOVEGRASS ( Eragrostis plana )

“…This alien African grass is the most abundant and aggressive invasive plant in the Pampa Biome, responsible for causing widespread economic impacts on livestock by modifying the structure of plant communities and by affecting ecological balances. The heterotoxicity of tough lovegrass was been observed in bioassays of seed germination with white clover (Trifolium repens), Italian ryegrass (Lolium multiflorum), African bristlegrass (Setaria sphacelata), and bahiagrass (Paspalum notatum) (Coelho, 1986;Ferreira et al, 2008;Favaretto et al, 2011). However, it was assumed that tough lovegrass may also display autotoxicity, because in the field, the clumps are separated from each other by empty spaces with bare soil radius of 5-10 cm (Coelho, 1986).…”

Growth and regrowth of tough lovegrass (Eragrostis plana Nees)

“…Its occurrence is common in overgrazed and excessively burned pasture (Brink, 2006), which amplifies its establishment and persistence, reducing the presence of species with better nutritive value. The species also presents active allelopathic mechanisms, inhibiting the germination and seedling growth of others species (Coelho, 1986;Favaretto et al, 2011). Medeiros & Focht (2007) suggested the possibility of restoring the natural pastures contaminated by this grass by manipulating grazing pressure of less selective herbivores, rotational grazing, deferment, protein/energetic supplementation, and strategic mowing to avoid seed production.…”