CHANGE IN ACTIVITY OF ANTIOXIDATIVE ENZYMES IN LEAVES OF ACACIA RETINODES, BIOTA ORIENTALIS AND CASUARINA EQUISETIFOLIA UNDER HEAT STRESS CONDITION

Terminal heat stress causes an array of physiological, biochemical and morphological changes in plants, which affect plant growth and development. Heat stress is one of the major abiotic stresses in agriculture worldwide. This study was carried out to investigate the effects of heat stress on soluble protein, catalase (CAT), and peroxidase (GPX) activities in three plant species (Casuarina equisetifolia, Acacia retinodes and Biota orientalis). Plants were randomly divided into two groups (the first group for heat stress treatment and the second for control) and heat stress treatments were applied at 36°C, 38°C, 40°C, 42°C and 44°C for 3h. Heat stress imposed significantly increased soluble protein content and CAT and GPX concentration in the three plants. These results suggest that CAT and GPX activities play an essential protective role against heat stress in Casuarina equisetifolia, Acacia retinodes and Biota orientalis. Antioxidants act as a major defense against radical mediated toxicity by protecting the damages caused by free radicals. An increase was observed in GPX and CAT activity of three plant species under stress conditions throughout the experiment. Results showed that CAT acts as the major antioxidant enzyme in Casuarina equisetifolia and Acacia retinodes leaves under oxidative stress condition and GPX was more important in Biota orientalis. So activity of these enzymes in stress condition can be used as an index for tolerance assessmen

Cartographic approach to regression of forest ecosystems in the area of Guerbes (Algeria) Author's Details: (1) Azzedine Hadef, (2) Nourreddine Mouhli, (3)

ABSTRACT This work is a diachronic study of the changing landscape occupying the land of the plain of Guerbes, which is localized in Skikda (north-east-Algerian

LES VARIATIONS THERMIQUES SAISONNIERS ET LEURS IMPACTS SUR LE COMPORTEMENT ÉCOPHYSIOLOGIQUES DES SEMIS DE PIN D’ALEP

In Algeria, the pine forests are concentrated mainly in arid and semi arid regions where the climatic conditions severely limit the production potential seriously, thus the mechanism of tolerance is the most effective strategy in situations of severe and prolonged stress. In this context, our study is to determine specifically the effect of seasonal temperature variations on Aleppo pine seedlings from biochemical markers such as the synthesis of proline, soluble sugars and chlorophyll. The results reveal a very significant accumulation of proline in aerial parts than in root during the summer and winter. Thus the accumulation of various osmolytes show that Aleppo pine stands as the most species-rich carbohydrates in winter and less rich in summer. Parallel to the accumulation of these solutes, a gradual decline of chlorophyll pigment content was recorded in winter and summer. In conclusion, the study reveals the thermophilic Aleppo pine and also shows that the solutes accumulated mark well the thermal limit of this species

EFFETS D’UNE TEMPERATURE FRAICHE ET D’UN APPORT EXOGENE DE REGULATEURS DE CROISSANCE SUR DES SEMIS DE CHENE LIEGE

The seedlings of Cork oak (Quercus suber L.) cultivated in uniform conditions at 25°C for a duration of long day of 16 hours are transferred for a week to a cool temperature of 5°C, to precise morphological stages. After coming back to initial conditions of cultivation, the temporal and spatial modifications are observed on waves. When the seedlings are transferred to “full bloom bud”, the caulinair strength phase last more time, and the component “rest period” is abolished. Concerning the other stages of transfer “swollen bud and rest period”, the duration of rest period and the formation of scales increase with the formation of semi-phase for the first stage. So, some spatio-temporel modifications appear, they are similar to those observed by the application of growth’s regulators of type gibberelic acid at full-bloom bud stage and rest period and cytokinine (kinetic) at swollen stage

Theoretical investigations of NiTiSn and CoVSn compounds

Link to publisher's homepage at http://www.elsevier.com/The structural, elastic and electronic properties of NiTiSn and CoVSn half-Heusler compounds have been calculated using the full-potential linear muffin-tin orbital (FP-LMTO) method. The computed equilibrium lattice constants are in excellent agreement with the available experimental and theoretical data. The elastic constants Cij are calculated using the total energy variation with strain technique. The polycrystalline elastic moduli (namely: the shear modulus, Young's modulus, Poisson's ratio, Lamé's coefficients, sound velocities and the Debye temperature) were derived from the obtained single-crystal elastic constants. The ductility mechanism for the studied compounds is discussed via the elastic constants Cij and their related parameters. The electronic band structure calculations show that the conduction band minimum (CBM) is located at the X point for both compounds, whereas the valence band maximum (VBM) is located at the Г point for NiTiSn and at the L point for CoVSn, resulting in indirect energy band gaps of 0.46 and 0.75 eV for NiTiSn and CoVSn, respectively. The pressure and volume dependences of the energy band gaps have been calculated

Probing the effect of different exchange-correlation functionals on the optoelectronic features of chalcogenide compound Ag2O

The primary goal of this study is to investigate the effect of different exchange-correlation functionals on the optoelectronic and elastic properties of the Ag2O chalcogenide compound. For the electronic structures and optical spectra, the Tran-Blaha modified Becke-Johnson approach combined with GGA and with GGA+U (mBJ-GGA-PBEsol and mBJ-GGA-PBEsol+U, respectively) was used. The available theoretical and experimental data for the bandgap energy were reported to determine whether there is a correlation with our results. The electronic structure revealed that our compound is a direct semiconductor at the R-symmetry point with a bandgap of 1.22 eV, which this value agrees well with the experimental values for the first time. The elastic constants were also evaluated using the IRelast package, which revealed that the compound was mechanically stable. Finally, the optical response was systematically studied, and it was found that Ag2O exhibited excellent optical efficiency.</jats:p