Herbicidal Activity of Thymbra capitata (L.) Cav. Essential Oil

[EN] The bioherbicidal potential ofThymbra capitata(L.) Cav. essential oil (EO) and its main compound carvacrol was investigated. In in vitro assays, the EO blocked the germination and seedling growth ofErigeron canadensisL.,Sonchus oleraceus(L.) L., andChenopodium albumL. at 0.125 mu L/mL, ofSetaria verticillata(L.) P.Beauv.,Avena fatuaL., andSolanum nigrumL. at 0.5 mu L/mL, ofAmaranthus retroflexusL. at 1 mu L/mL and ofPortulaca oleraceaL., andEchinochloa crus-galli(L.) P.Beauv. at 2 mu L/mL. Under greenhouse conditions,T. capitataEO was tested towards the emergent weeds from a soil seedbank in pre and post emergence, showing strong herbicidal potential in both assays at 4 mu L/mL. In addition,T. capitataEO, applied by spraying, was tested againstP. oleracea,A. fatuaandE. crus-galli. The species showed different sensibility to the EO, beingE. crus-gallithe most resistant. Experiments were performed againstA. fatuatestingT. capitataEO and carvacrol applied by spraying or by irrigation. It was verified that the EO was more active at the same doses in monocotyledons applied by irrigation and in dicotyledons applied by spraying. Carvacrol effects onArabidopsisroot morphology were also studied.This research was supported by the Universitat Politècnica de València [project number: SP20120543], by Generalitat Valenciana [project number GV/2014/039], and by the Spanish Ministry of Science, Innovation and Universities [project number: RTI2018¿094716¿B¿I00]. Thanks to Jovano Erris Nugroho and Muhamad Iqbal who collaborate to carry out in vivo experiment 4 during their internship in the Plant Health in Sustainable Cropping Systems Erasmus+ Programme. This research work has been developed as a result of a mobility stay funded by the Erasmus+-KA1 Erasmus Mundus Joint Master Degrees Programme of the European Commission under the PLANT HEALTH Project. 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Phytotoxic activity of the natural compound norharmane on crops, weeds and model plants

Norharmane is a secondary metabolite that appears in different species of land plants. In this paper, we investigated for the first time the specificity of norharmane through germination and growth tests on some crops as Zea mays L. (maize), Triticum aestivum L. (wheat), Oryza sativa L. (rice) and Lactuca sativa L. (lettuce) and weeds as Amaranthus retroflexus L. (amaranth), Echinochloa crus-galli L. (barnyard grass), Plantago lanceolata L. (ribwort), Portulaca oleracea L. (common purslane) and Avena fatua L. (wild oat), and its phytotoxic capacity on the metabolism of adult Arabidopsis thaliana L. (thale cress) by measuring chlorophyll a fluorescence, pigment content, total proteins, osmotic potential and morphological analysis. Norharmane had an inhibitory effect on the germination of A. fatua and P. lanceolata, and the growth of P. oleracea, E. crus-galli and A. retroflexus. On adult A. thaliana plants, the compound was more effective to watering, leading to water stress that compromised the growth of the plants and ultimately affected the photosynthetic apparatus. Therefore, this research shows that norharmane not only affects seedlings’ metabolism, but also damages the metabolism of adult plants and can be a potential model for a future bioherbicide given its specificity.Ministerio de Ciencia e Innovación | Ref. FPU14-02243Ministerio de Economía y Competitividad | Ref. AGL2013-41281-

Rosmarinic acid induces programmed cell death in Arabidopsis seedlings through reactive oxygen species and mitochondrial dysfunction

Phytotoxic potential of rosmarinic acid (RA), a caffeic acid ester largely found in aromatic species, was evaluated on Arabidopsis through metabolomic and microscopic approaches. In-vitro bioassays pointed out that RA affected root growth and morphology, causing ROS burst, ROS scavengers activity inhibition and consequently, an alteration on cells organization and ultrastructure. In particular, RA-treatment (175 μM) caused strong vacuolization, alteration of mitochondria structure and function and a consistent ROS-induced reduction of their transmembrane potential (ΔΨm). These data suggested a cell energy deficit also confirmed by the metabolomic analysis, which highlighted a strong alteration of both TCA cycle and amino acids metabolism. Moreover, the increase in H2O2 and O2− contents suggested that RA-treated meristems underwent oxidative stress, resulting in apoptotic bodies and necrotic cells. Taken together, these results suggest that RA inhibits two of the main ROS scavengers causing high ROS accumulation, responsible of the alterations on mitochondrial ultrastructure and activity through ΔΨm dissipation, TCA-cycle alteration, cell starvation and consequently cell death on Arabidopsis seedlings. All these effects resulted in a strong inhibition on root growth and development, which convert RA in a promising molecule to be explored for further use in weed management.Xunta de Galicia | Ref. GRC2015/01

Rosmarinic acid induces programmed cell death in Arabidopsis seedlings through reactive oxygen species and mitochondrial dysfunction.

Phytotoxic potential of rosmarinic acid (RA), a caffeic acid ester largely found in aromatic species, was evaluated on Arabidopsis through metabolomic and microscopic approaches. In-vitro bioassays pointed out that RA affected root growth and morphology, causing ROS burst, ROS scavengers activity inhibition and consequently, an alteration on cells organization and ultrastructure. In particular, RA-treatment (175 μM) caused strong vacuolization, alteration of mitochondria structure and function and a consistent ROS-induced reduction of their transmembrane potential (ΔΨm). These data suggested a cell energy deficit also confirmed by the metabolomic analysis, which highlighted a strong alteration of both TCA cycle and amino acids metabolism. Moreover, the increase in H2O2 and O2- contents suggested that RA-treated meristems underwent oxidative stress, resulting in apoptotic bodies and necrotic cells. Taken together, these results suggest that RA inhibits two of the main ROS scavengers causing high ROS accumulation, responsible of the alterations on mitochondrial ultrastructure and activity through ΔΨm dissipation, TCA-cycle alteration, cell starvation and consequently cell death on Arabidopsis seedlings. All these effects resulted in a strong inhibition on root growth and development, which convert RA in a promising molecule to be explored for further use in weed management