Enhancing sustainability through microalgae cultivation in urban wastewater for biostimulant production and nutrient recovery.

Microalgae can produce biostimulants in form of phytohormones, which are compounds that, even if applied in low concentrations, can have stimulant effects on plants growth and can enhance their quality and their resistance to stress. Considering that microalgal biomass can grow recovering nutrients from wastewater, this circular approach allows to use residues for the production of high added value compounds (such as phytohormones) at low cost. The interest on biostimulants production from microalgae have recently raised. Scientists are focused on the direct application of these cellular extracts on plants, while the number of studies on the identification of bioactive molecules, such as phytohormones, is very scarce. Two cyanobacteria strains (Synechocystis sp. (SY) and Phormidium sp. (PH)) and a chlorophyte (Scenedesmus sp. (SC)) were cultured in laboratory-scale PBRs with a working volume of 2.5 L in secondary urban wastewater varying N:P ratio in the cultures to obtain the highest productivity. The variation of N:P ratio affects microalgae growth, and SY and PH presented higher productivities (73 and 48 mg L-1 d, respectively) under higher N:P ratio (> 22:1). Microalgal biomass was freeze-dried and phytohormones content was measured with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The three microalgae showed similar phytohormones profiles, being the auxin (indole-3-acetic acid, IAA) the most abundant (72 ng g-1DW in SY). Proteins were major macronutrient for all strains, reaching 48 %DW in PH culture. To optimize the biostimulants production, a balance between the production of such compounds, biomass productivity and nutrients removal should be taken into consideration. In this sense, SC was the most promising strain, showing the highest N and P removal rates (73 % and 59 %, respectively) while producing phytohormones.

A revision of the Solanum elaeagnifolium clade (Elaeagnifolium clade; subgenus Leptostemonum, Solanaceae).

The Solanum elaeagnifolium clade (Elaeagnifolium clade) contains five species of small, often rhizomatous, shrubs from deserts and dry forests in North and South America. Members of the clade were previously classified in sections Leprophora, Nycterium and Lathyrocarpum, and were not thought to be closely related. The group is sister to the species-rich monophyletic Old World clade of spiny solanums. The species of the group have an amphitropical distribution, with three species in Mexico and the southwestern United States and three species in Argentina. Solanum elaeagnifolium occurs in both North and South America, and is a noxious invasive weed in dry areas worldwide. Members of the group are highly variable morphologically, and this variability has led to much synonymy, particularly in the widespread S. elaeagnifolium. We here review the taxonomic history, morphology, relationships and ecology of these species and provide keys for their identification, descriptions, full synonymy (including designations of lectotypes) and nomenclatural notes. Illustrations, distribution maps and preliminary conservation assessments are provided for all species.

ResumenEl clado Elaeagnifolium contiene cinco especies arbustivas, usualmente rizomatosas, distribuidas en desiertos y bosques secos de Norte y Sudamérica. Previamente, los miembros del clado estuvieron agrupados en las secciones Leprophora, Nycterium y Lathyrocarpum porque se pensaba que no estaban estrechamente relacionados. El grupo es hermano de los Solanum del Viejo Mundo (Old World clade). Las especies del grupo tienen una distribución anfitropical, con tres especies de México y el Suroeste de Estados Unidos y tres especies en Argentina. Solanum elaeagnifolium se encuentra en Norte y Sudamérica, y es conocida como una nociva hierba invasora en áreas secas de todo el mundo. Los miembros de este grupo son altamente variables en su morfología, lo cual ha llevado a la existencia de mucha sinonimia, particularmente en S. elaeagnifolium. Aquí revisamos la historia taxonómica, morfología, relaciones y ecología de estas especies; así mismo, proveemos claves para su identificación, descripción, sinonimia completa (incluyendo las designaciones de lectotipos) y notas nomenclaturales. Además proveemos ilustraciones, mapas y evaluaciones del estado de conservación de las especies.