Uptake and accumulation of emerging contaminants in soil and plant treated with wastewater under real-world environmental conditions in the Al Hayer area (Saudi Arabia)

Tetraena mandavillei L. is a perennial shrub native to the Middle Eastern countries of Asia, which is extensively regarded as a drought-tolerant plant. However, the plant reduces growth and biomass when grown in high concentrations of sodium chloride in the soil. We conducted a pot experiment to influence the negative impact of different levels of salinity (0, 10, and 20 dSm-1 ) and drought stress (100, 80, 60, and 40% water field capacity), to study different growth-related parameters, physiological alterations and ion uptake by T. mandavillei. Both salinity and drought stress caused a negative impact by affecting several attributes of T. mandavillei, but the plants showed some resistance against drought stress conditions in terms of growth and biomass. In addition to that, we noticed that a combinatorial and individual impact of drought and salinity stress decreased photosynthetic pigments and gas exchange parameters in T. mandavillei. Results also depicted that the combination of the abiotic stress conditions drought and salinity induced reactive oxygen species (ROS), indicating that the plants undergo oxidative damaged. However, due to the active plant defense system, the plant enhanced its performance under abiotic stress conditions, but due to the severe drought condition (40% water field capacity), a significant (P < 0.05) decrease in the activities of antioxidant compounds was caused. Furthermore, osmolytes also increased under both salinity and drought stress conditions in this study. Our results also showed that increased salinity and drought stress in the soil caused a significant increase in sodium (Na+ ) and chloride (Cl- ) ions in roots and shoots of T. mandavillei. In contrast to that, the contents of Calcium (Ca2+ ) and potassium (K+ ) were decreased in all organs of the plants with increasing levels of salinity and drought stress. Taken together, T. mandavillei can be classified as a facultative halophyte with the ability to tolerate drought stress and using salt accumulation mechanisms to tolerate salinity stress.

Negative impact of long-term exposure of salinity and drought stress on native Tetraena mandavillei L

A falta de saneamento basico traz diversos problemas, sendo um dos mais importantes a alteracao da qualidade da agua, um recurso essencial para a vida. Deste modo, objetivou-se com esse trabalho determinar os parâmetros para dimensionamento de um sistema alternativo de tratamento de esgoto para comunidades rurais e o aproveitamento desse efluente em culturas agricolas, associando-se tratamento de esgoto de baixo custo, interacao a paisagem local e potencial produtivo com uso de fertirrigacao. Para isso, os ensaios experimentais foram realizados em duas etapas sendo a primeira: montagem de unidades piloto de tratamento, utilizando a tecnica de sistemas alagados construidos (SACs), constituidos de 18 unidades experimentais - cochos plasticos, nas dimensoes de 0,70 m de largura x 2,10 m de comprimento x 0,31m de altura, e com declividade longitudinal de 0,05m m-1, preenchidos com meio suporte (brita #1, D60= 12mm, coeficiente de uniformidade - CU D60/D10 = 3,8 e volume de vazios inicial de 0,520m-3 m-3), utilizando fluxo do liquido subsurperficial horizontal. Os sistemas foram submetidos a dois metodos sendo aplicado taxas de carregamento orgânico de 100, 200 e 300 kg. ha-1.d-1 de DBO e diferentes tempos de detencao hidraulicos (1, 2 e 4 dias), cultivados com tres forrageiras capim-elefante (Napier - Pennisetum purpureum schum.), capim Mombaca (Megathyrsus maximus) e capim Tifton 85 (Cynodon spp.). E a segunda etapa, foi o aproveitamento agricola do efluente tratado, o qual foi montado o sistema de irrigacao e fertirrigacao em uma area de 100m², utilizando o metodo de irrigacao por gotejamento composto por mangueiras de polietileno com 0,016 m de diâmetro, dotados de gotejadores autocompensantes integrados no espacamento de 0,50 m (um gotejador por planta), cuja vazao era de 1,9 L h-1 para a pressao de servico de 10 Mpa. O experimento foi conduzido em delineamento inteiramente ao acaso com quatro tratamentos e tres repeticoes, sendo baseado na quantidade de sodio do efluente, assim os tratamentos foram 1- Testemunha- irrigacao com agua limpa (ausencia aplicacao de esgoto), T2 - Fertirrigacao fornecendo 150 kg ha-1 ano-1 de sodio com efluente tratado, T3 - Fertirrigacao fornecendo 300 kg ha-1 ano-1 de sodio com efluente tratado e T4 - Fertirrigacao fornecendo 150 kg a ha-1 ano-1 de sodio com esgoto bruto. Os resultados possibilitaram concluir que: o sistema alagado construido, SAC3 com as caracteristicas taxa de carga orgânica igual a 100 kg DBO5 ha-1dia-1, tempo de detencao hidraulico de 5,6 dias e vegetacao o capim-tifton-85 proporcionou melhor eficiencia em diversos aspectos, sendo o sistema escolhido para a segunda etapa. Em relacao a fertirrigacao da cultura do milho foi verificado que a aplicacao do esgoto bruto proporciona a menor produtividade, sendo o uso do efluente tratado o mais indicado. A fertirrigacao com o esgoto, utilizando o sistema de gotejo, e indicada para o uso desse efluente, uma vez que nao ocorre o contato direto com o fruto produzido, assim como verificado neste estudo, o qual os graos de milho apresentaram otima qualidade sanitaria, ou seja, livre de coliformes termotolerantes. Em relacao ao solo, verificou-se melhorias nos aspectos fisicos onde a densidade do solo reduziu, levando ao aumento dos demais: volume total de poros, densidade de particulas e condutividade hidraulica, tendo assim uma melhora na estrutura do solo.

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Desenvolvimento de um sistema ecológico para tratamento e aproveitamento agrícola de esgoto doméstico em comunidades rurais

Proline accumulation is a widespread response of plants to salt stress as well as drought and cold stress. In most plant species, two isoforms of pyrroline-5-carboxylate synthetase (P5CS) catalyze the first step in proline biosynthesis from glutamate. In Arabidopsis, these isoforms differ in their spatial and temporal expression patterns, suggesting sub-functionalization. P5CS1 has been identified as the major contributor to stress-induced proline accumulation, whereas P5CS2 has been considered important for embryo development and growth. In contrast to previous results, our analysis of P5CS1- and P5CS2-GFP fusion proteins indicates that both enzymes were exclusively localized in the cytosol. The comparison of the susceptibility of p5cs1 and p5cs2 mutants to infection with Pseudomonas syringae and salt stress provided novel information on the contribution of the two P5CS isoforms to proline accumulation and stress tolerance. In agreement with previous studies, salt-stressed p5cs1 mutants accumulated very little proline, indicating that P5CS1 contributed more to stress-induced proline accumulation, whereas its impact on stress tolerance was rather weak. Germination and establishment of p5cs2 mutants were impaired under ambient conditions, further supporting that P5CS2 is most important for growth and development, whereas its contribution to stress-induced proline accumulation was smaller than that of P5CS1. In contrast to p5cs1 mutants or wildtype plants, p5cs2 mutants were only weakly affected by sudden exposure to a high NaCl concentration. These findings show that proline content, which was intermediate in leaves of p5cs2 mutants, was not directly correlated with stress tolerance in our experiments. In rosettes of NaCl-exposed p5cs2 mutants, nearly no accumulation of Na+ was observed, and the plants showed neither chlorosis nor reduction of photosynthesis. Based on these data, we suggest a function of P5CS2 or P5CS2-mediated proline synthesis in regulating Na+ accumulation in leaves and thereby salt stress tolerance.

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Differential Contribution of P5CS Isoforms to Stress Tolerance in Arabidopsis.

Salinity stress effects on transpiration and plant growth under different salinity soil levels based on thermal infrared remote (TIR) technique

Impact of drought and salinity on olive water status and physiological performance in an arid climate

Physiological improvements of young olive tree (Olea europaea L. cv. Chetoui) under short term irrigation with treated wastewater

Plants are subjected to many stresses (salinity, drought, heavy metals, temperature, etc.) that may limit their growth. As a result, plants exhibit a variety of adaptive strategies to mitigate the adverse effects of abiotic stresses. Among those strategies, the accumulation of compatible solute such as proline is the most common defensive mechanism adopted. Indeed, proline plays a highly beneficial role as an osmolyte. In addition, proline helps to stabilize subcellular structures and acts as a metal chelator. Proline may also activate the cellular antioxidant system and scavenge the reactive oxygen species (ROS). Accordingly, application of exogenous proline was investigated on plants to induce tolerance. Therefore, under salt conditions, exogenous proline might alleviate growth inhibition and ameliorate photosynthetic activity, mineral nutrition, and water status. Furthermore, it may regulate osmotic potential and decrease the effect of toxic ions by activating the enzymatic antioxidant system. Exogenous proline applied under drought stress has successfully improved physiological performance. In these conditions, these applications increased proline accumulation in cells and therefore reduce cell osmotic potential and maintain turgor. This osmotic adjustment may help plants to improve their biomass. Finally, the beneficial role of exogenous proline was also proved in plants subjected to metal stress. This organic compound may reduce the phytotoxic effects of metals through the formation of proline-metal complexes and the stimulation of enzymatic and nonenzymatic antioxidant systems. Besides, exogenous proline may protect plants subjected to metal contamination by stabilizing membranes and thereby preventing electrolyte leakage, improving water status, photosynthetic activity, and growth rate.

Exogenous Proline-Mediated Abiotic Stress Tolerance in Plants: Possible Mechanisms

Potential effects of arbuscular mycorrhizal fungi in mitigating the salinity of treated wastewater in young olive plants (Olea europaea L. cv. Chetoui)

Effect of arbuscular myccorhizal fungi on soil properties, mineral nutrition and antioxidant enzymes of olive plants under treated wastewater irrigation

Ameni Ben Hassena

Papers

Impact of drought and salinity on olive water status and physiological performance in an arid climate

Physiological improvements of young olive tree (Olea europaea L. cv. Chetoui) under short term irrigation with treated wastewater

Exogenous Proline-Mediated Abiotic Stress Tolerance in Plants: Possible Mechanisms

Potential effects of arbuscular mycorrhizal fungi in mitigating the salinity of treated wastewater in young olive plants (Olea europaea L. cv. Chetoui)

Effect of arbuscular myccorhizal fungi on soil properties, mineral nutrition and antioxidant enzymes of olive plants under treated wastewater irrigation