Search Results

You are looking at 1 - 7 of 7 items for

  • Author or Editor: H. Moussa x
  • All content x
Clear All Modify Search

The effect of gamma irradiation on Vicia faba L. plants was investigated by exposing dry seeds to doses ranging from 0 to 100 Gray (Gy) and studying the activities and isozyme patterns of the key enzymes involved in oxidative stress defence, such as superoxide dismutases (SOD, EC 1.15.1.1), catalases (CAT, EC 1.11.1.6), peroxidases (POX, EC 1.11.1.7), ascorbate peroxidases (APOX, EC 1.11.1.11), monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) and glutathione reductase (GR, EC 1.6.4.2), as well as the activity of an enzyme involved in a specific intermediary metabolic pathway, glucose-6-phosphate dehydrogenase (G 6 PDH, EC 1.1.1.49). The H 2 O 2 contents of faba bean leaves were also measured. None of the γ-irradiation doses used (0–100 Gy) had any effect on the activity of MDHAR, but they increased the enzyme activities of GR, APOX, SOD and G 6 PDH. Gamma rays at 20 Gy decreased the H 2 O 2 content, but the 100 Gy dose significantly increased the H 2 O 2 content compared with the non-irradiated plants. The results implied that the isozymes of SOD, CAT and POX present in faba bean cells growing in the presence of 0–15 Gy γ-irradiation are required to remove the reactive oxygen species (ROS) produced during normal, physiological processes. When the dose of γ-irradiation is ≥20 Gy, the level of ROS (produced indirectly by γ-irradiation) becomes too high to be dealt with by the existing antioxidant isozymes. The present research shows for the first time that the switch between the physiological oxidative response and a stress-related one occurs within a very narrow range of stress factor intensities, i.e. γ-irradiation doses. In the present study, this change took place between 15 and 20 Gy. Further investigations, using molecular biology techniques will be needed to determine the mechanisms involved in enzyme induction under ionizing conditions in order to evaluate changes in the gametic genomes at two possible levels: (i) the structural level, for studying mutations occurring in the DNA, and (ii) the functional level, by studying differential genetic expression between irradiated and non-irradiated plants.

Restricted access

Drought stress is the main limiting factor in soybean production. However, no work has been done on how the application of a low dose of gamma rays could help to overcome water deficits during critical stages of soybean development. Gamma rays at a dose of 20 Gray (Gy) were applied to dry seeds of soybean before planting. Two levels of soil moisture (80% field capacity for well-watered control and 35% for drought-stressed treatment) were applied at pod initiation. Gamma irradiation increased biomass accumulation and seed yield in both treatments. It also increased the chlorophyll content, photosynthetic activity (14CO2 fixation) and leaf water potential and enhanced the enzyme activities of RuBPCase and PEPCase of control plants compared with drought-stressed plants. Gamma irradiation (20 Gy) increased the soluble sugars, protein and proline content and the activities of peroxidase and superoxide dismutase in drought-stressed soybean leaves. It also increased the chloroplast size, which was reduced by drought treatment, and rebuilt, to some extent, the chloroplast ultrastructure. However, it decreased the malondialdehyde concentration and the electrical conductivity of the leaves under drought stress. Overall, the results indicated that pre-treatment with gamma rays (20 Gy) to dry seeds of soybean before planting could be used to enhance drought tolerance and minimize the yield loss caused by water deficit.

Restricted access

It was found that diploid seedless watermelon can be produced by pollination with partially functional pollen which was irradiated with gamma rays at doses of 600 and 800 Gray (Gy). The diploid seedless fruit was very similar to normal fruit in days to maturity from pollination and rate of fruit set. The number of empty seeds in the diploid seedless fruit varied for the cultivars used in this study. No correlation was found between the number of empty seeds in seedless fruit and the number of normal seeds in normal fruit. Also, the results indicated that seedless watermelon cultivars have a significant increase in total sugar and carotenoids (lycopene and β-carotene) content, providing an important source of phytonutrients in the diet. The pollen tube of pollen irradiated with gamma radiation penetrated normally into the synergid and sperm cells were discharged. Subsequently, the egg nucleus and sperm nucleus became attached to each other in the egg cell and a globular embryo was formed. However, the embryo failed to differentiate into organ tissues and degenerated. It was suggested that seedless fruit induced by gamma rays had a beneficial effect in increasing the quantity and quality of watermelon yield via increases in the carotenoid, total sugar content and fruit weight. Also, in some cultivars there was a tendency for the thickness of the rind to decrease.

Restricted access

Irradiation stress adversely affects plant growth and development. No radioprotective activity of glycinebetaine (GB) has yet been reported in plants. When applied pre-sowing to dry seeds of fenugreek, gamma rays at doses of 0, 25, 50, 100 and 150 Gray (Gy) from a cobalt ( 60 Co) source with a strength of 500 Ci and a dose rate of 0.54 Gy/min significantly reduced the chlorophyll content, total protein, photosynthetic efficiency ( 14 CO 2 fixation), total dry weight, and accumulation of reducing, non-reducing and total soluble sugars in comparison with the un-irradiated control. It also significantly repressed the activities of hydrolytic enzymes (α-amylase and invertase) and the carboxylating enzyme (ribulose-1,5-bisphosphate-carboxylase/oxygenase) in the fenugreek plants. Soaking irradiated seeds with glycinebetaine (50 mM) for 24 hours partially alleviated the depression effects of irradiation in these parameters. Gamma irradiation significantly increased the H 2 O 2 content, while pre-soaking irradiated seeds with GB significantly decreased the H 2 O 2 level. The magnitude of the reversal declined as the irradiation dose increased.Gamma irradiation induced a significant decrease in the level of nucleic acids (DNA and RNA), accompanied by a corresponding induction of the hydrolytic activities of DNase and RNase in comparison with the un-irradiated control. These changes were more significant at higher γ-ray doses. Post-treatment of irradiated seeds with GB partially alleviated the adverse effects of radiation, significantly increasing nucleic acid levels and repressing the activities of DNase and RNase. The protective role played by glycinebetaine was more significant at lower γ-ray doses. Pre-treatment of seeds with GB may play an effective role in the radio-repair mechanism.

Restricted access

The effect of CdCl2(0-50 µM) on the growth, physiological parametersand leaf antioxidative enzymes of faba bean plants was studied in order toinvestigate the possible involvement of this metal in the generationof oxidative stress. In the roots and leaves of faba bean plants Cd produceda significant inhibition of growth, as well as a reduction inthe transpiration rate, photosynthetic efficiency (14CO2-fixation), ribulose-1,5-bisphosphate-carboxylase/oxygenase (Rubisco) activity and leaf pigment content, and an alteration in the nutrient status in booth roots and leaves. an increased level of free proline was also detected. The results suggest thatthe treatment of faba bean plants with CdCl2 induced a concentration-dependentoxidative stress situation in the leaves, characterized by an accumulationof  H2O2, as a result of theinhibition of the antioxidant enzymes glutathione reductase (GR) and catalase (CAT). These results point to the possible inductionof leaf senescence by cadmium.

Restricted access

Treatment with CdCl 2 (0, 100, 400 and 1000 μM) resulted in the inhibition of root dry biomass and root elongation and to increased Cd accumulation in the roots. These treatments also decreased the relative water content, chlorophyll content, 14 CO fixation, phosphoenol pyruvate carboxylase and ribulose-1,5-bisphosphate carboxylase activity and abscisic acid (ABA) content, while increasing the malondialdehyde, hydrogen peroxide and free proline contents and causing changes in the chloroplast and root ultrastructure. Pretreatment of seeds with SA (500 μM) for 20 h resulted in the amelioration of these effects.

Restricted access

Abstract  

Electrodeposition of tellurium from metal salt solutions in the presence of phthalic acid and inorganic substances at controlled pH has been investigated. The current density ranged from 0.28 to 11.34 mA cm–2. The percentage cathodic current efficiency was relatively low and increased with increasing concentration of tellurion ions in the bath. The purity of the deposited metal was better than 99%. X-ray diffraction analysis shows that the deposit belongs to the hexagonal structure.

Restricted access