Ferjani Ben Abdallah

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.

Adaptive biochemical and physiological responses of Eriobotrya japonica to fluoride air pollution

The biochemical and physiological effects of fluoride were investigated in loquat trees (Eriobotrya japonica) grown in the vicinity of a phosphate fertilizer plant in Tunisia. Photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (E), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities were assessed; along with photosynthetic pigments, lipid peroxidation, electrolytic leakage (EL) and total phenolic contents in foliage and roots of trees at different distances from the phosphate fertilizer plant. All assessed parameters showed significant discrepancies in comparison with unpolluted sites. Obtained results showed high oxidative stress indices including H2O2, lipid peroxidation, and EL, SOD, CAT and GPx activities and proline contents in leaves and roots at the polluted sites as compared to control. In contrast, leaf Pn, Gs, E and photosynthetic pigment contents were low as compared to the control. These results indicate that even though antioxidant responses increased near the factory, adverse effects on physiology were pronounced.

Leaf biochemical responses and fruit oil quality parameters in olive plants subjected to airborne metal pollution

This study was carried out in two olive orchards (Olea europaea L., cv. Chemlali) located in a polluted area near a fertilizers factory and in a control unpolluted site, managed with similar cultivation techniques. The aim was to investigate the physiological and biochemical responses of polluted plants (PP), exposed to atmospheric metal contamination (Cd, Cu, Fe, Mn, Ni and Pb) as compared to control plants (CP). Leaves, roots and fruits of PP showed a depression of their non-enzymatic and enzymatic antioxidant defences and a disruption of their hormonal homeostasis. The anomalous physiological status of PP was also demonstrated by the lower values of pigments in leaves and fruits, as compared to CP. Atmospheric metals negatively affected olive oil chemical and sensory quality. However, despite metal deposition on fruit surfaces, the accumulation of potentially toxic metals in olive oil was negligible. Considering that olive oil is an important food product worldwide and that many productive olive orchards are exposed to several sources of pollution, this work could contribute to clarify the effects of atmospheric metal pollution on olive oil quality and its potential toxicity for humans.

Morphological and physiological changes induced in Olea europaea and Prunus dulcis exposed to air fluoride pollution

Air quality biomonitoring using plant leaves has been widely applied to assess the effects of atmospheric pollution. The present study was conducted to investigate the effects of gaseous hydrogen fluoride on the tree leaves of Prunus dulcis and Olea europaea around a phosphate fertilizer-producing factory constituting a major source of pollution. The photosynthesis rate, damaged leaf areas, fluoride accumulation, stomatal architecture and some biochemical responses in the leaves of O. europaea and P. dulcis, were measured. Based on visible injury, gas exchange, stomata responses and certain biochemical parameters, P. dulcis was a sensitive species, and O. europaea was tolerant. Our studies showed that fluoride had a potential effect on stomatal plasticity and confirmed the presence of different control mechanisms for pollution on each leaf surface. It was observed that evergreen tree species highly tolerated fluoride pollutants present in the air, and therefore can be effective in reducing pollutants concentration to a safer level in the environment.

Effect of the phosphogypsum amendment of saline and agricultural soils on growth, productivity and antioxidant enzyme activities of tomato (Solanum lycopersicum L.)

The objective of this study was to investigate the effects of phosphogypsum (PG) amendment on the physiochemical proprieties of saline and agricultural soils along with the growth, productivity and antioxidant enzyme activities of tomato plants (Solanum lycopersicum L.) grown on the amended soils under controlled conditions. Obtained results showed that the amendment of saline soil (H) by PG induced a decrease in pH as well as in electrical conductivity. However, for the non saline soil (MC), there was a decrease in pH associated with an increase in electrical conductivity. For both soils, PG amendment led to an increase in Calcium (Ca) and sodium (Na), and a decrease in potassium (K) in plant tissues. Cadmium (Cd), Zinc (Zn) and Chromium (Cr) contents in different parts of plants increased in proportion with PG concentration in the soils. Apart from Cd, all the analyzed metals in tomato fruit were found to be below the recommended maximum allowable concentration (MAC). Our results showed that PG application, at doses not exceeding 20%, seems to be beneficial for growth, photosynthetic activity and productivity of tomato plants as well as in decreasing salinity of saline soils. In these conditions, the use of PG could be a promising project for the rehabilitation of marginalized and saline ecosystems with either ornamental or non-fruit species. For both soils, a significant accumulation of MDA in shoots was detected, reflecting cell membrane damage especially when the PG amendment reached 20%. Beyond 20 and 40% PG, tomato plants developed an enzymatic antioxidant defense system in response to salinity and heavy metal stress. However, at 80% PG, enzymes activities were significantly inhibited.

Exogenous Proline Improves Olive Plant Performance Against Cadmium Stress

Among heavy metals, cadmium (Cd) when released in soil, is harmful as it can easily penetrate the root system and reach plant photosynthetic tissues.

Follow-up of fluorine pollution effect on grapevine

Effects of atmospheric pollution on three local grapevines, Asli, Jerbi and Tounsi, growing in the vicinity of a phosphate fertiliser factory, consist of an exhibition of characteristic necrosis on leaves and fruits. Analysis of necrotic leaf areas allowed us to distribute local vines into sensitivity classes. The follow-up, in function of time and space, of stomatal conductance and leaf fluoride content during the different seasons allowed us to reveal some offensive strategies allowing these vines to escape from pollutants toxicity and maintaining its vitality. Therefore, giving that fluorine is strange to its metabolism, grapevine tends to accumulate it, thanks to an external concentration mechanism, in the tips and leaf margins. Necrotic areas are delimited by a narrow brown border line. Thus, allowing the plant not only to avoid F - toxicity, but also to keep a big assimilation surface. In addition, possibilities as F - excluding, F - vacuol partitioning, temporary closing of stoma, F - trapping as CaF2, SiF4 are also to be considered. By another way, our results seem to show that full mature grapevine leaves may constitute an efficient tool to assess fluorine pollution impact. Berries contamination seems to be affected directly by the factory smoke, there is no endogenous supply. Likewise, by its characteristic necrosis in the leaf boundaries, grapevine may be considered as a bioindicator variety of fluorine pollution which can be used in mapping polluted areas.