Pascal Labrousse

Impact of proline application on cadmium accumulation, mineral nutrition and enzymatic antioxidant defense system of Olea europaea L. cv Chemlali exposed to cadmium stress

Proline plays an important role in plant response to various environmental stresses. However, its involvement in mitigation of heavy metal stress in plants remains elusive. In this study, we examined the effectiveness of exogenous proline (10 and 20 mM) in alleviating cadmium induced inhibitory effects in young olive plants (Olea europaea L. cv. Chemlali) exposed to two Cd levels (10 and 30 mg CdCl2 kg(-1) soil). The Cd treatment induced substantial accumulation of Cd in both root and leaf tissues and a decrease in gas exchange, photosynthetic pigments contents, uptake of essential elements (Ca, Mg and K) and plant biomass. Furthermore, an elevation of antioxidant enzymes activities (superoxide dismutase, catalase, glutathione peroxydase) and proline content in association with relatively high amounts of hydrogen peroxide, thiobarbituric acid reactive substances and electrolyte leakage were observed. Interestingly, the application of exogenous proline alleviated the oxidative damage induced by Cd accumulation. In fact, Cd-stressed olive plants treated with proline showed an increase of antioxidant enzymes activities, photosynthetic activity, nutritional status, plant growth and oil content of olive fruit. Generally, it seems that proline supplementation alleviated the deleterious effects of young olive plants exposed to Cd stress.

Exogenous proline mediates alleviation of cadmium stress by promoting photosynthetic activity, water status and antioxidative enzymes activities of young date palm (Phoenix dactylifera L.)

The ability of exogenous compatible solutes, such as proline, to counteract cadmium (Cd) inhibitory effects in young date palm plants (Phoenix dactylifera L. cv Deglet Nour) was investigated. Two-year-old date palm plants were subjected for five months at different Cd stress levels (0, 10 and 30 mg CdCl2 kg(-1) soil) whether supplied or not with exogenous proline (20mM) added through the irrigation water. Different levels of Cd stress altered plant growth, gas exchanges and chlorophyll content as well as water status, but at different extent among them. In contrast, an increase of antioxidant enzymes activities of Cd-treated plants in association with high amounts of proline content, hydrogen peroxide (H2O2), thiobarbituric acid reactive substances (TBARS) and electrolyte leakage (EL) were observed. Interestingly, exogenous proline mitigated the adverse effects of Cd on young date palm. Indeed, it alleviated the oxidative damage induced by Cd accumulation and established better levels of plant growth, water status and photosynthetic activity. Moreover, proline-treated plants showed high antioxidant enzymes activities (superoxide dismutase, catalase and glutathione peroxydase) in roots and leaves as compared to Cd-treated plants.

Soil fluoride spiking effects on olive trees (Olea europaea L. cv. Chemlali).

A pot experiment under open air conditions was carried out to investigate the uptake, accumulation and toxicity effects of fluoride in olive trees (Olea europaea L.) grown in a soil spiked with inorganic sodium fluoride (NaF). Six different levels (0, 20, 40, 60, 80 and 100mM NaF) of soil spiking were applied through NaF to irrigation water. At the end of the experiment, total fluoride content in soil was 20 and 1770mgFkg(-1) soil in control and 100mM NaF treatments, respectively. The comparative distribution of fluoride partitioning among the different olive tree parts showed that the roots accumulated the most fluoride and olive fruits were minimally affected by soil NaF spiking as they had the lowest fluoride content. In fact, total fluoride concentration varied between 12 and 1070µgFg(-1) in roots, between 9 and 570µgFg(-1) in shoots, between 12 and 290µgFg(-1) in leaves, and between 10 and 29µgFg(-1) in fruits, respectively for control and 100mM NaF treatments. Indeed, the fluoride accumulation pattern showed the following distribution: roots>shoots>leaves>fruits. On the other hand, fluoride toxicity symptoms such as leaf necrosis and leaf drop appeared only in highly spiked soils (60, 80 and 100mM NaF).

Micropropagation of Myriophyllum Alterniflorum (Haloragaceae) for Stream Rehabilitation: First In Vitro Culture and Reintroduction Assays of a Heavy-Metal Hyperaccumulator Immersed Macrophyte

Nowadays, submersed aquatic macrophytes play a key role in stream ecology and they are often used as biomonitors of freshwater quality. So, these plants appear as natural candidates to stream rehabilitation experiments. Among them, the stream macrophyte Myriophyllum alterniflorum is used recently as biomonitor and is potentially useful for the restoration of heavy-metal contaminated localities. The best way to obtain a mass production of watermilfoil plants is micropropagation. We developed in vitro culture of M. alterniflorum and the effects of five media on the plant development were assessed. Five morphological and four physiological endpoints were examined leading to the recommendation of the Murashige and Skoog medium for ecotoxicological studies on chlorophyllous parts, and of the Gaudet medium for root cytotoxicity and phytoremediation studies. Micropropagated clones were acclimatized in a synthetic medium and in situ reintroduction was performed efficiently. This is the first report of micropropagated plants transplantation in streams. The successful establishment of watermilfoil beds even in polluted areas strongly suggested that ecological restoration using micropropagated watermilfoil is a promising biotechnology for phytoremediation and rehabilitation of degraded areas. Moreover, high bioconcentration factors evidenced that watermilfoil hyperaccumulates Cd and Cu, and could be potentially used in phytoremediation studies.

The most powerful multivariate normality test for plant genomics and dynamics data sets

Data analysis methods like analysis of variance and regression in plant sciences depend on the assumption that the biological data are normal. Using a normality test is the best way to check whether the distribution is normal or not. Plant genomic and dynamic studies generate data with leptokurtic distribution and the most appropriate normality test is the Shapiro-Francia one. However multivariate extensions of this test have not been designed yet and plant data matrix cannot be performed efficiently or without bias. Thus, our analysis focused on the development of an easy-using algorithm to extend the application of the Shapiro-Francia test to multivariate data matrix in plant studies.

Halotolerance in Lichens: Symbiotic Coalition Against Salt Stress

Lichens are among the most conspicuous and ubiquitous symbiosis on this planet. They are highly adapted to terrestrial habitats of all climatic zones including the most hostile environments on Earth, such as high altitudes in the Himalayas or the cold deserts of Antarctica. Among the extreme habitats are the littoral (or intertidal) zones of coasts. In this chapter, we present an overview of the current knowledge about the halotolerance mechanisms in lichens. Halotolerant organisms generally accumulate osmotically active solutes to cope with increasing external salinity. In intertidal lichens, mannitol could play an important role in osmoregulation. Epilichenic bacterial colonies may be also involved in limiting lichen nutrient imbalance by producing osmoprotective compounds and storing high ionic concentrations. In addition, the comparison with related inland species suggests that morphological adaptations could also be involved in adaptation to increased salt levels. Maritime species often have strongly conglutinated hyphae and small or no intercellular spaces in their thalli. So far, little genetic information exists about the genes involved in halotolerance and their regulation. Comparison of forthcoming genomic information from lichen fungi with those of other halotolerant fungi will soon help to change the picture and reveal genetic adaptations to saline environments.

HPLC method for the analysis of α -tocopherol from Myriophyllum alterniflorum

0009-3130/11/4704-0679 2011 Springer Science+Business Media, Inc. 1) University of Limoges, Faculty of Pharmacy, Laboratory of Botany & Cryptogamy, GRESE EA 4330, 2 rue du Docteur Marcland, F-87025 Limoges, France, fax: +33 555 435 850, e-mail: david.delmail@wanadoo.fr; 2) University of Limoges, Faculty of Sciences, GRESE EA 4330, 123 avenue Albert Thomas, F-87060 Limoges, France. Published in Khimiya Prirodnykh Soedinenii, No. 4, p. 594, July–August, 2011. Original article submitted April 7, 2010. Chemistry of Natural Compounds, Vol. 47, No. 4, September, 2011 [Russian original No. 4, July–August, 2011]

Prorocentrum rivalis sp. nov. (Dinophyceae) and its phylogenetic affinities inferred from analysis of a mixed morphological and LSU rRNA data set

A new freshwater epiphytic Prorocentrum species, Prorocentrum rivalis, from the temperate region of the Haute-Vienne, France, is described. This species is the third freshwater species identified among approximately 60 marine Prorocentrum species. This new species is described using scanning electron microscope and phylogenetic analyses by a polyphasic approach (LSU rRNA sequences combined with 9 morphological characters). The phylogenetic analysis attests that P. rivalis is close to other planktonic freshwater species and the freshwater Prorocentrum clade is evolutionarily derived from an epiphytic freshwater prorocentroid ancestor. The unique marine species in the freshwater clade results from an ecophysiological reversion. P. rivalis differs from other epiphytic taxa by its rarity, its temperate distribution and its ecophysiological needs. The phylogeny confirms also that all planktonic Prorocentrum species are evolutionarily derived from epiphytic/benthic ancestors.

Heavy-Metal Attack on Freshwater Side: Physiological Defense Strategies of Macrophytes and Ecotoxicological Ops

For many years, strong anthropogenic pollutions like heavy metals induce deep changes in all ecosphere compartments especially in streams where deleterious effects on aquatic plants are noted. Indeed, ionic interactions on whole plant surface and permanent replacement of metal pool lead to ecophysiological disruptions among freshwater macrophytes. To prevent from irreversible alterations, macrophytes develop a typical antioxidant systems (e.g., proteins, secondary metabolites, metabolic pathways) to protect intracellular components from reactive oxygen species and to preserve major biosynthesis pathways like photosynthesis. These macrophytes also accumulate solutes to cope with increasing external metal toxicity. Moreover, new anatomical features reducing water stress and leading to cell homeostasis can appear in leaves, as a double endodermis. Tolerance to heavy metals is an interesting feature of freshwater plants for understanding any adaptation and acclimation processes to highly ionic concentrated environments at the genetic level. Indeed, specific genes involved in the synthesis of molecular chaperones might be related to heavy-metal tolerance in macrophytes. Due to their metal sensitivity and bioaccumulation capabilities, these organisms appear essential in ecotoxicological studies like biomonitoring to manage natural habitats.

Plant ageing, a counteracting agent to xenobiotic stress

A xenobiotic can be defined as any chemical or other substance that is not normally found in the ecosystems or that is present at concentrations harmful to all biological organisms. This general definition could be applied to anthropogenic and naturally occurring constituents. Organic contaminants can include pesticides, solvents and petroleum products. Inorganic xenobiotics include heavy metals, nonmetals, metalloids, radionuclides and simple soluble salts (Schwab, 2005).