Ricinus communis as a phytoremediator of soil mineral oil: morphoanatomical and physiological traits.

Rapid growth in the oil industry has been accompanied concomitant increases in risks of spills or leaks triggered by natural or anthropogenic causes that cause soil changes and plant damage. Bio-scavenging and phytoremediation plants are important tools for identifying pollutants and mitigating environmental damage. The objective of this study was to evaluate the phytoremediation potential of Ricinus communis cultivated in soils contaminated with mineral oil, and to determine the possible visual, anatomical and physiological effects. R. communis seeds were pre-germinated in individual pots containing Red Latosol contaminated with Lubrax Essential SL (15W-40) mineral oil at concentrations of 0 (control), 5, 10, and 15 g kg-1. After exposure to treatments, emergency evaluations were performed, and after 45 days of cultivation, visual, morphoanatomical, physiological and oil removal effects were evaluated. There was no difference in emergence showed between treatments. Visual effects were characterized by necrosis and chlorosis formation in R. communis, evidenced on the 45th day of cultivation in all treatments tested, followed by parenchymal tissue alterations with collapsed cell formation and damage to photosynthesis with increasing doses. We found that R. communis removed up to 81% of hydrocarbons in soils, classifying it as potential phytoremediator of contaminated soils. The strong correlation between the variables suggests that R. communis can be used as an indicator of pollutant action.

Hormetic Effect Caused by Sublethal Doses of Glyphosate on Toona ciliata M. Roem.

This study aimed to evaluate the response of Toona ciliata seedlings to sublethal doses of glyphosate. The increasing use of glyphosate in agriculture concerns the scientific community, as the drift of this pollutant into aquatic systems or atmospheric currents can affect non-target species. Therefore, we need to understand how non-target species respond to small doses of this herbicide. T. ciliata seedlings (clone BV-1110) were exposed to sublethal doses of glyphosate (0, 9.6, 19.2, 38.4, 76.8 g ae ha-1). Anatomical, physiological, and photochemical analyses were performed 60 days after herbicide application, and growth assessments were carried out after 160 days of cultivation. We found that sublethal doses of glyphosate above 19.2 g ae ha-1 induced toxicity symptoms in Toona ciliata leaves. These symptoms were mild in some cases, such as chlorosis, but severe in other cases, such as tissue necrosis. We observed a positive relationship between increased plant height and photochemical yield with plant exposure to sub-doses 9.6 and 19.2 g ae ha-1. A sublethal dose of 38.4 g ae ha-1 improved the photosynthetic rate and carboxylation efficiency. Thus, we confirmed the hypothesis of a hormetic effect when T. ciliata was exposed to sub-doses of glyphosate equal to or lower than 38.4 g ae ha-1. However, the sublethal dose of 76.8 g ae ha-1 must be considered toxic, impacting photosynthetic activity and, consequently, the height of T. ciliata. The stem diameter of T. ciliata responded positively to increasing glyphosate doses. This occurs to compensate for the negative effect of glyphosate on water absorption. Further research will provide valuable information for harnessing the potential benefits of hormesis to improve the productivity of T. ciliata.

Bioindicator potential of Ricinus communis to simulated rainfall containing potassium fluoride.

BACKGROUND: Fluoride pollution is a global problem because of its high phytotoxicity. Fluoride is released in air, water and soil through industrial processes, where it damages various plant species. Ricinus communis is widely distributed in Brazil, India and China and has been extensively used as a phytoremediation species in heavy metal-contaminated soils. However, few studies regarding the effect of air pollutants on R. communis have been published, and no information about the exposure of this species to fluoride is available. Therefore, the aim of the present study was to investigate the effects of fluoride on R. communis morphoanatomical and physiological responses using simulated rainfall containing potassium fluoride (KF). METHODS: Young plants at approximately 10 days after emergence were treated daily with KF using simulated rainfall at 0, 1.5, 3.0 and 4.5 mg L-1, for 37 consecutive days. Chlorophyll a fluorescence, gas exchange, anatomical characteristics and fluoride accumulation in the roots and leaves were evaluated after this period. RESULTS: No visual or anatomical symptoms were observed for the first three treatments. Necrosis and chlorosis were visually evident after the 37th day of KF application at 4.5 mg L-1, followed by changes in parenchyma tissues, cell collapse and phenolic compound accumulation at the end of the experiment. No damage was observed in terms of photosynthetic photochemical and biochemical stages. Maintenance of physiological characteristics in the presence of fluoride accumulation in roots and leaves were shown to be important fluoride biomarkers. These characteristics suggest that R. communis is tolerant to 1.5 and 3.0 mg L-1 KF, and is anatomically sensitive at 4.5 mg L-1 KF.

Métodos de superação de dormência em sementes de croada (Mouriri elliptica Mart) / Dormancy breaking methods in croada (Mouriri elliptica Mart) seeds

Sementes de croada (Mouriri elliptica Mart.) Melastomataceae, espécie frutífera nativa do cerrado, foram submetidas aos seguintes tratamentos, visando a superação de dormência: pré-resfriamento a 5° C por 7 dias; pré-aquecimento em estufa com circulação de ar a 40º C por 7 dias; escarificação química em ácido sulfúrico concentrado por 5 e 15 minutos; imersão em água fervente por 5 e 15 minutos; imersão em ácido giberélico a 100 e 200 mg L-1 por 48 horas; imersão em água destilada por 24 e 48 horas; escarificação mecânica com lixa nº 80 na parte superior e oposta ao eixo embrionário e testemunha (sementes sem tratamento prévio). Quatro repetições de quinze sementes foram colocadas para germinar sobre papel umedecido com água destilada ou nitrato de potássio a 0,2 por cento, em temperatura de 30º C em presença de luz. Foram realizadas contagens diárias do 2º dia após a implantação do experimento até a estabilização da porcentagem de germinação, que acorreu no 60º dia. A germinação foi mais rápida em sementes pré-embebidas em ácido giberélico (em substrato umedecido com água ou com solução de nitrato de potássio 0,2 por cento), pré-embebidas em água por 24 horas, em substrato umedecido com água, e pré-embebidas em água por 48 horas ou escarificadas mecanicamente e colocadas para germinar em substrato umedecido com água. Taxas de germinação mais elevadas ocorreram em sementes pré-embebidas em ácido giberélico a 100 ou 200 mg L-1, em substrato umedecido com solução de nitrato de potássio 0,2 por cento.

Croada seeds (Mouriri elliptica Mart.) Melastomataceae, a fruit-bearing species native of the cerrado (savannah-like vegetation), were submitted to the following dormancy breaking methods: pre-cooling at 5° C for 7 days; pre-heating in a oven air circualtion at 40º C for 7 days; chemical escarification in concentrated sulfuric acid for 5 and 15 min; soaking in boiling water for 5 and 15 min; soaking in gibbereli acid at 100 and 200 mg L-1 for 48 hours; soaking into distilled water for 24 and 48 hours; mechanical escarification with a sandpaper number 80 at teh upper aprt and opposed to the embryonary axis and control (seeds without any previous treatment). The seeds were put to germinate on a "germitest" type paper moistened with destilled water or 0.2 percent potassiun nitrate. Daily counts between the 2nd day after the establishment of the experiment till the stabilization, which took place on the 60th day, were performed. Seeds germinated faster when they were pre-soaked in gibberelic acid, independent of if placed to germinate on a water-moistened substrate or with a soultion of 0.2 percent potassiun nitrate, pre-soaked into water for 24 hours, on a water-moistened substrate, or independent of the substrate, and, pre-soaked into water for 48 hours or mechanical escarification and put to germinate on a water-containing substrate. Higher germination rates occurred in seeds pre-soaked into 100 or 200 mg L-1 gibberelic acid, on a substrate moistend with a 0.2 percent potassiun nitrate containing solution.