Marine metal pollution and effects on seaweed species

© Springer International Publishing AG 2017. Heavy metals are significant pollutants continuously released into the biosphere, both naturally and anthropogenically. Conceptually, metal speciation, bioavailability, and associated toxicity in marine organisms depend on a wide array of abiotic and biotic factors. Among these, pH variation is one of the most important environmental factors influencing metal speciation and toxicity. Due to this, ocean acidification is expected to modify metal speciation, altering the effects these nondegradable contaminants have on marine organisms, such as seaweeds. One clear effect of heavy metals on seaweeds is the rapid formation of reactive oxygen species (ROS). The production of ROS beyond the physiological tolerance threshold causes an oxidative stress condition that, if not attenuated, can irreversibly damage cellular constituents such as DNA/RNA, proteins, and lipids. To cope with heavy metal excess, several mechanisms exist in tolerant seaweed species, including the activation of an efficient ROS-scavenging system constituted by metal-binding compounds, antioxidant enzymes, and oxygenated polyunsaturated fatty acids, among others. Another adaptive mechanism involves the participation of ATP-binding cassette (ABC) transporter proteins in translocating a wide variety of compounds across cell membranes, including heavy metals. In contrast, an excessive heavy metal presence can inhibit photosynthesis, reduce pigment concentration and growth, induce cation losses, and disrupt gametophyte development in non-tolerant seaweed species. In a scenario of lowered ocean pH and increased heavy metal toxicity, the important roles played by non-tolerant seaweed species in structuring communities could be severely compromised, with unknown consequences for associated organisms. Therefore, in the upcoming decades, marine pollution could majorly shift and rearrange community compositions and the distributional ranges of species

A Novel Aspect of Essential Oils: Coating Seeds with Thyme Essential Oil induces Drought Resistance in Wheat

Coating seeds with biostimulants is among the promising approaches in crop production to increase crop tolerance to drought stress. In this study, we evaluated the potential of coating durum wheat seeds of the cultivar lsquo;Karimrsquo; with thyme essential oil on enhancing seed germination and seedling growth, and on plant growth promotion and induction of drought resistance. Coated seeds were pre-germinated, grown in hydroponics, and grown in pots under controlled well-watered and progressive water/nutrient stress conditions. Seed coating with thyme oil increased germination rate and enhanced seedling growth development in hydroponics. In the pot experiment, thyme oil increased, when well watered, root and shoot development, chlorophyll, nitrogen balance index (NBI), abscisic acid (ABA), anthocyanins and flavonoids in leaves, decreased nitrogen isotope composition (delta;15N) and increased carbon isotope composition (delta;13C) of shoots. Increasing water/nutrient stress in control plants induced higher accumulation of ABA and anthocyanins coupled with a transient decrease in chlorophyll and NBI, a decrease in shoot and root development, the Normalized Difference Vegetation Index (NDVI), shoot C content, delta;15N, and an increase in delta;13C, revealing the avoidance strategy adopted by the cultivar. Thyme oil had the potential to enhance the avoidance strategy by inducing roots elongation, reducing the loss of shoot and roots dry matter and chlorophyll, maintaining balanced NBI, an decreasing anthocyanins, flavonoids, and delta;13C via maintaining lower ABA-mediated-stomatal closure. Thyme oil increased shoot N content and delta;15N indicating preferential uptake of the 15N enriched NH4+. Coating seeds with thyme oil is suggested as a promising alternative approach to improve plantrsquo;s water and nutrient status and to enhance drought resistance

Non-foliar photosynthesis and nitrogen assimilation influence grain yield in durum wheat regardless of water conditions

19 páginas, 1 tabla, 9 figurasThere is a need to generate improved crop varieties adapted to the ongoing changes in the climate. We studied durum wheat canopy and central metabolism of six different photosynthetic organs in two yield-contrasting varieties. The aim was to understand the mechanisms associated with the water stress response and yield performance. Water stress strongly reduced grain yield, plant biomass, and leaf photosynthesis, and down-regulated C/N-metabolism genes and key protein levels, which occurred mainly in leaf blades. By contrast, higher yield was associated with high ear dry weight and lower biomass and ears per area, highlighting the advantage of reduced tillering and the consequent improvement in sink strength, which promoted C/N metabolism at the whole plant level. An improved C metabolism in blades and ear bracts and N assimilation in all photosynthetic organs facilitated C/N remobilization to the grain and promoted yield. Therefore, we propose that further yield gains in Mediterranean conditions could be achieved by considering the source-sink dynamics and the contribution of non-foliar organs, and particularly N assimilation and remobilization during the late growth stages. We highlight the power of linking phenotyping with plant metabolism to identify novel traits at the whole plant level to support breeding programmes.This work was supported by the Spanish Ministry of Science and Innovation (projects PID2022-138307OB-C2 and PID2019-107154RB-I00), and by the Junta de Castilla y León and co-financed by the European Regional Development Fund (projects CSI260P20 and CLU-2019-05-IRNASA/CSIC Unit of Excellence). RV acknowledges support from the Max Planck Society and FCT – Fundação para a Ciência e a Tecnologia, I.P., through the Programme ‘Concurso de Estímulo ao Emprego Científico Institucional’ (CEECINST/00102/2018/CP1567/CT0039, https://doi.org/10.54499/CEECINST/00102/2018/CP1567/CT0039), GREEN-IT—Bioresources for Sustainability R&D Unit—Base Funding (UIDB/04551/2020, https://doi.org/10.54499/UIDB/04551/2020), and the LS4FUTURE Associated Laboratory (LA/P/0087/2020). SCK is supported by a Ramon y Cajal research fellowship (RYC-2019-027818-I) from the Spanish Ministry of Science and InnovationPeer reviewe