Herbicidal Effects and Cellular Targets of Aqueous Extracts from Young Eucalyptus globulus Labill. Leaves

Abstract

Eucalyptus globulus Labill. is a widespread exotic species that contributes to the formation of fire-prone environments, a great concern under climate change conditions. Therefore, sustainable practices to help locals managing eucalyptus stands are needed. In this perspective, harnessing eucalyptus’ specialized metabolism as a source of allelochemicals can be a promising approach for weed control. Thus, the main goals of this work were to evaluate the herbicidal potential of post-fire regenerated E. globulus leaves against Portulaca oleracea L. and to unravel the physiological mechanisms behind this phytotoxic action. For this, aqueous extracts of fresh (FLE; 617 g FW L−1) or oven-dried leaves (DLE; 250 g DW L−1) were foliar-sprayed at different dilutions in purslane seedlings. After five weeks, results revealed that DLE at the highest dose detained the greatest herbicidal activity, affecting purslane growth and cellular viability. Moreover, biochemical data pointed towards an overproduction of reactive oxygen species, causing harsh oxidative damage in roots, where the upregulation of important cellular players, like sugars, amino acids, and proline, was not able to reestablish redox homeostasis. Overall, this study proved that dried leaves from young E. globulus had potent herbicidal properties against P. oleracea and can represent a feasible strategy for weed management.

Phytochemical Properties and Diverse Beneficial Roles of Eucalyptus globulus Labill.: A Review

“…Therefore, the allelopathic compatibility between crops and Eucalyptus trees must be essentially checked to avoid the potential adverse effects of trees on the associated crops. Additionally, the aqueous extract of the oven-dried leaves has a herbicidal potential as a biocide against the widespread weed of Portulaca oleracea L., which is attributable to the existence of a significant amount of allelochemicals [86]. The above-mentioned results recommend that the bioactive compounds present in Eucalyptus plants must be further investigated in weed control, as bioherbicides, with possible commercial applications.…”

Untargeted metabolomic profiling of fresh and dried leaf extracts of young and mature Eucalyptus globulus trees indicates differences in the presence of specialized metabolites

“…This suggests a high potential interest in dried leaf extracts, especially from young trees, for use as a natural herbicide. In fact, in a recent study, it was revealed that aqueous extracts prepared with dried leaves from young E. globulus foliar-applied, twice-a-week at 250 g L -1 had potent herbicidal activities against purslane seedlings, used as a model weed species ( Pinto et al., 2021 ). The differences in the content of hydrolysable tannins in the tested extracts were pointed out as a possible cause for the high allelopathic activity of dried E. globulus leaf extracts when compared with that of fresh leaf extracts.…”

“…One of these portions was immediately oven-dried at 60°C until reaching a constant weight. Then, fragments of fresh and dried leaves from young and mature trees collected in the three different sites (i.e., Y1, Y2, Y3, A1, A2, and A3 from Figure 1 ) suffered an extraction procedure in deionized water at 70°C, for 30 min, according to the methodology of Pinto et al. (2021) .…”

“…Besides these widely recognized biological activities, volatile terpene compounds can be released into the environment, affecting the presence and development of surrounding plants, in a process known as allelopathy ( May and Ash, 1990 ; Singh et al., 1991 ; Reigosa et al., 2000 ). This can be of particular interest when applied to weed control in a sustainable agriculture context ( Pinto et al., 2021 ). Additionally, eucalyptus leaves detain several phenolic compounds such as ellagitannins like ellagic acid, hydroxycinnamic and hydroxybenzoic acids, flavonols like rutin, quercetin, catechin, and kaempferol 3-O-glucoside, as well as appreciable amounts of phenolic acids as it is the case of gallic and benzoic acids ( Boulekbache-Makhlouf et al., 2013 ; Puig et al., 2018 ).…”

Herbicide Use in the Era of Farm to Fork: Strengths, Weaknesses, and Future Implications

“…Regarding soil management, tillage, stale seedbed, and dead mulches have been proposed to reduce infestations and seedbank presence (Pinke et al, 2018 ; Jensen, 2019 ; Menegat and Nilsson, 2019 ; Fracchiolla et al, 2021 ; Nikolić et al, 2021 ; Zeller et al, 2021 ). Mowing, hoeing, and flaming (Gerhards et al, 2020 ;Mainardis et al, 2020 ;Spaeth et al, 2020 ;Hofmeijer et al, 2021 ), as well as the use of beneficial microorganisms, biocontrol agents and bioherbicides (Boari et al, 2016 ; Giannini et al, 2021 ; Pinto et al, 2021 ) could be used in site-specific direct control. Finally, state-of-the-art artificial intelligence technologies, weed mapping, and decision support systems (DSS) facilitate the monitoring of weed communities, and the rapid and informed decision-making (Sønderskov et al, 2015 ; Halstead et al, 2021 ; Jurado-Expósito et al, 2021 ).…”