Search

Soil contamination by heavy metals is considered as one of the major environmental issues in recent years as it poses a threat to agricultural production due to their adverse effects on plant growth, food quality and environmental health. Pollution by heavy metals involves metal ions which are not always essential to plants as they affect growth and development. The application of a chelating agent, EDTA, increases the absorption of heavy metals by increasing their phytoavailability. Our results showed that lead and nickel have a negative impact on peas (Pisum sativum) as they affect their germination rate, plant growth and protein content. EDTA itself also causes the same negative effects as heavy metals since it represents a toxic xenobiotic substance. The combination of this chelator with Ni or Pb amplified the action of these heavy metals on the various parameters studied. The Oxidative stress is manifested through the accumulation of reactive oxygen species and MDA which is an indication of cellular membranes alteration. The enzymatic activities of catalase, ascorbate peroxidase and superoxide dismutase were stimulated by EDTA, heavy metals or a combination of the two. In addition, the activity of the glutathione S-transferase was greatly increased in response to EDTA and both heavy metals. [ABSTRACT FROM AUTHOR]

Seed treatment is often used for improving germination performance, growth parameters and tolerance to abiotic stresses. Thus, the seeds can undergo chemical pretreatments by imbibition in the presence of certain molecules such as sodium nitroprusside (nitrogen monoxide donor) and calcium chloride (Ca2+ being involved in signaling). Hydropriming is a pregermination treatment which helps in stopping imbibition before the end of the reversible phase of germination, i.e before the start of the lengthening of the radicle. Our results showed an improvement in the germination performance and growth of fenugreek (Trigonella foenum-greacum L.) seedlings when treated in the same manner. These improvements were accompanied by the formation of reactive oxygen species (hydrogen peroxide and superoxide). Measurements of the antioxidative activities of catalase, ascorbate peroxidase, superoxide dismutase and guaiacol peroxidase showed strong stimulation in the radicles of pre-treated or hydroprimed seeds. This activity was stronger in hydroprimed seeds compared to the control and chemical treatment. Thus the improvement in germination performance and growth seems to be linked to the oxidative stress observed during germination. [ABSTRACT FROM AUTHOR]

Norflurazon 100 µM alone or in combination with α-tocopherol (0.25 mM) was applied in pre-emergence of peanut seedlings (Arachis hypogaea L.). Norflurazon treatment allowed to partially or totally photobleach plants which were noticeably smaller than the control. Norflurazon impaired the photosynthetic activity by decreasing photosynthetic pigments (carotenoids and chlorophylls) and by reducing quantities of soluble sugar. The determination of malondialdehyde (MDA) showed that its content was higher in treated plants in relation with enhancement of reactive oxygen species by the herbicide and decreased the endogenous α-tocopherol. The addition of exogenous a-tocopherol reduced the damage done by the herbicide at the membrane level because of the MDA content was less important than in norflurazon treated seedlings. Furthermore, the norflurazon decreased the glutathione S-transferase (GST) activity in the leaves and the roots of peanut seedlings, while it increased the level of reduced glutathione. This activity decreased even more with the application of exogenous α-tocopherol in combination with the herbicide. The herbicide alone or in association with the antioxidant α-tocopherol increased ascorbic acid content. The supplementation of α-tocopherol did not decrease the phytotoxicity of norflurazon although we observed a decrease in MDA content. [ABSTRACT FROM AUTHOR]

This experiment was conducted to determine the effect of exogenous proline (20 mM) on the physiological and biochemical behavior of durum wheat seedlings subjected to a salt constraint (10 g/l NaCl). This effect was evaluated through the estimation of plant water status (leaf relative water content), photosynthetic pigments, sugars content, water soluble proteins content, the osmotic adjustment (endogenous proline and glycine betaine), the lipid peroxidation (the membrane integrity and the malondialdehyde content) and the activity of the antioxydant enzyme catalase in wheat plantlets. Results obtained show that the saline stress affects the majority of the studied parameters. However, exogenous application of proline seems to attenuate the negative effects of the saline stress by the improvement of the content of total chlorophyll, proteins, glycine betaïne and the relative electrolyte leakage. These results suggest the capacity of the exogenous application of proline to improve the tolerance of the saltstressed wheat plants. [ABSTRACT FROM AUTHOR]

Plant Growth Promoting Rhizobacteria (PGPR) can play important role in agriculture. The objective of this study was to assess the ability of the isolated strain Pseudomonas putida to improve physiological and biochemical parameters of durum wheat seedlings (Triticum durum Desf. Var. Mohamed Ben Bachir) and helped them to withstand bleaching herbicide the norflurazon. At 10-4 M, the norflurazon induced the bleaching of seedlings (photobleaching). At the physiological level, it caused the inhibition of carotenoids (0.03±0.01 mg g-1), chlorophylls (0.15±0.03 mg g-1) and carbohydrates (0.28±0.07 mg g-1) contents. At the cellular level, carotenoids defiency angendred by the norflurazon induced oxidative stress which manifested by an increase of MDA content (32.33±2.08 mmoles g-1), a lipid peroxidation marker, as well as a sharp increase in the electrolytes leakage (63.7±6.01 %) sign of membrane systems deterioration. The norflurazon also decreased the catalase (7.13 μmol H2O2 mn-1mg -1of proteins) and glutathion S-transferase (2 nanomol min-1mg-1 of proteins) activities in the leaves of durum wheat seedlings. The strain of Pseudomonas putida with inherent phosphate solubilizing activity, auxins (IAA) synthesis and EPS production was inoculated to the wheat seedlings in the presence and absence of norflurazon. It had eased phytotoxic effects of norflurazon on wheat seedlings and improving theirs physiology and their antioxidant mechanisms. The bacteria strain used would so represent a valuable partner in the future agriculture by its bioprotective and biostimulating properties. [ABSTRACT FROM AUTHOR]

Norflurazon is a bleaching herbicide known to block carotenoid biosynthesis by inhibiting phytoene desaturase activity. Soybean plants were treated with norflurazon, and we examined the effects on the desaturation of lipid molecular species in leaves using ammonium [1-(14)C] oleate labeling. In monogalactosyldiacylglycerol (MGDG), the main chloroplast lipid, a decrease in 18:3/18:3 molecular species and an increase in its precursors 18:2/18:3 and 18:2/18:2 were observed suggesting that the omega(3) FAD7 desaturase activity in planta was inhibited by norflurazon. The in vitro activity of MGDG synthase was also inhibited by 69%. In contrast, the amount of 18:3/18:3 molecular species of phosphatidylcholine (PC) in the extraplastid compartment increased. The observed increase in in vitro lysoPC-acyltransferase activity and activation of desaturation of [1-(14)C] oleate suggest that extraplastid omega(3)FAD3 desaturase was activated. Analysis of the expression of omega(3) FAD3 and omega(3) FAD7 genes in norflurazon treated plants indicate that omega(3) FAD7 and omega(3) FAD3 desaturases are controlled at the post-transcriptional level.