Jalal M. Basahi

Gas exchange and chlorophyll fluorescence of pea (Pisum sativum L.) plants in response to ambient ozone at a rural site in Egypt

Egyptian pea cultivars (Pisum sativum L. cultivars Little Marvel, Perfection and Victory) grown in open-top chambers were exposed to either charcoal-filtered (FA) or non-filtered air (NF) for five consecutive years (2009-2013) at a rural site in northern Egypt. Net photosynthetic rates (PN), stomatal conductance (gs), intercellular CO2 (Ci) and chlorophyll fluorescence were measured. Ozone (O3) was found to be the most prevalent pollutant common at the rural site and is suspected to be involved in the alteration of the physiological parameters measured in the present investigation. PN of different cultivars were found to respond similarly; decreases of 23, 29 and 39% were observed in the cultivars Perfection, Little Marvel and Victory, respectively (averaged over the five years) due to ambient O3. The maximum impairment in PN was recorded in the cultivar Victory (46%) in 2013 when the highest O3 levels were recorded (90 nL L(-1)). The average stomatal conductance decreased by 20 and 18% in the cultivars Little Marvel and Perfection, respectively, while the average stomatal conductance increased on average by 27% in the cultivar Victory. A significant correlation was found between PN and Ci, indicating the importance of non-stomatal limitations of photosynthesis, especially in the cultivar Victory. The PN vs. Ci curves were fitted to a non-rectangular hyperbolic model. The actual quantum yield (ΦPSII) and photochemical quenching coefficient (qP) were significantly decreased in the leaves of plants exposed to NF air. Non-photochemical quenching (NPQ) was increased in all cultivars. Exposure to NF air caused reductions in chlorophyll (Chl a) of 19, 16 and 30% in the Little Marvel, Perfection and Victory cultivars, respectively.

Effects of Enhanced UV-B Radiation and Drought Stress on Photosynthetic Performance of Lettuce (Lactuca sativa L. Romaine) Plants

Aims: The aim of the present study was to investigate some biochemical changes in field grown lettuce (Lactuca sativa L. cv Romaine) plants in terms of importance of the accumulation of anthocyanins, flavonoids and photosynthetic pigments as well as photosynthetic limitations which changed during exposure of plants to drought stress and UV-B radiation in order to circumvent the deleterious effects of these Stresses. Place and Duration of Study: The experiment was conducted under filed conditions from November 2012 to January 2013, at the Agricultural Research Center, KAU. Methodology: The experimental design was a factorial arrangement in randomized complete blocks with four replicates. The first factor was UV-B (300 nm). The second factor was irrigation regime (complete irrigation to field capacity and limited irrigation. Gas exchange measurements were carried out using a LI-6200 portable IRGA. Chlorophyll fluorescence of Fv/Fm was measured by PAM 2000 fluorometer. Biochemical analyses and antioxidant enzymes assays were performed according to the appropriate methods. Results: Exposure of lettuce plants to enhanced UV-B radiation and drought stresses (DS) negatively and significantly affected the process of photosynthesis including CO2 assimilation (PN), stomatal conductance to water vapour (gs) and transpiration rate (E). However, the amplitude of the effects of both stressors was dependent on the interactions. This resulted in alleviation of the negative effect of drought on photosynthesis and transpiration by UV-B radiation as the water stress intensified. Intercellular CO2 (Ci) concentration was only reduced due to water stress compared to control plants. The maximum efficiency of photosystem II (Fv/Fm) was not affected by UV-B radiation stress but reduced by drought. There was an increase in the activities of some antioxidant due to both stresses when applied singly and in combination UV-B irradiation increased the contents of the UV-B absorbing compounds (carotenoids, soluble phenols, anthocyanins), while drought stress caused a notable increase in free proline content. Increase in content of Proline may be the drought-induced factor which plays a protective role in response to UV-B. Conclusion: UV-B radiation provoked in general more severe damage, evaluated as changes in the amounts of stress markers, than DS, when applied separately. Under multiple stress conditions, each of the stress factors seems to bring out some adaptive effects to reduce the damage experienced by plants caused by the other one. DS can induce accumulation of UV-B absorbing compounds (flavonoids, carotenoids and soluble phenols), which is likely to offer some increased protection from UV-B.

Relationship of polycyclic aromatic hydrocarbons with oxy(quinone) and nitro derivatives during air mass transport

Airborne concentrations of Polycyclic Aromatic Hydrocarbons (PAH), quinone and nitro derivatives have been measured at three sites on the coast of Saudi Arabia to the north of the city of Jeddah. The PAH show a general reduction in concentrations from northwest to southeast, consistent with a source from a petrochemical works to the northwest of the sampling sites. In comparison, the concentrations of quinones show little variation between the sampling sites consistent with these being predominantly longer lived secondary pollutants formed from PAH oxidation. The nitro-PAH show a gradient in concentrations similar to but smaller than that for the PAH suggesting a balance between atmospheric formation and removal by photolysis. The 2-nitrofluoranthene:1-nitropyrene ratio increases from north to south, consistent with atmospheric chemical formation of the former compound, while the ratio of 2-nitrofluoranthene:2-nitropyrene is consistent with hydroxyl radical as the dominant reactant. An investigation of the changes in PAH congener ratios during air mass transport along the Red Sea coast shows consistency with reaction with a relatively low concentration of hydroxyl radical only for the day with the highest concentrations. It is concluded that while PAH degradation is occurring by chemical reaction, emissions from other locations along the air mass trajectory are most probably also leading to changes in congener ratios.

Organohalogenated contaminants in sediments and bivalves from the Northern Arabian Gulf

Several classes of Organohalogenated contaminants (OHCs) were determined in sediments and bivalves collected from Kuwait coast. The levels and profile of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs) were compared in both sediments and bivalves. PCB-153 and -138 were the major contributors towards total OHCs followed by DDT and its metabolites (DDTs). The higher contribution of DDTs (~40%) and BDE-47 (~15%) in bivalves as compared to that in associated sediments indicated high biota-sediment accumulation factors (BSAF). Higher BSAF (values for heavier PCBs, DDTs and PBDEs) also indicated their high accumulation potential from sediment into associated biota at most of the studied locations. Overall, OHCs in sediments and bivalves measured in current study were lower than those reported in the literature worldwide. Most of the sediment concentrations of OHCs (ng/g, dry weight) were in the range of permissible guideline values proposed by Canadian Sediment Quality Guidelines (CSQGs), with few exceptions for DDTs (5 ng/g) and PCBs (22.7 ng/g). Similarly, 10% of bivalve samples contained high levels (ng/g, lipid weight) of PCBs (300) and DDTs (150) and were above the set safety benchmarks. This study establishes baseline for future monitoring programs.

Toxicity of iron oxide nanoparticles to grass litter decomposition in a sandy soil

We examined time-dependent effect of iron oxide nanoparticles (IONPs) at a rate of 2000 mg kg−1 soil on Cynodon dactylon litter (3 g kg−1) decomposition in an arid sandy soil. Overall, heterotrophic cultivable bacterial and fungal colonies, and microbial biomass carbon were significantly decreased in litter-amended soil by the application of nanoparticles after 90 and 180 days of incubation. Time dependent effect of nanoparticles was significant for microbial biomass in litter-amended soil where nanoparticles decreased this variable from 27% after 90 days to 49% after 180 days. IONPs decreased CO2 emission by 28 and 30% from litter-amended soil after 90 and 180 days, respectively. These observations indicated that time-dependent effect was not significant on grass-litter carbon mineralization efficiency. Alternatively, nanoparticles application significantly reduced mineral nitrogen content in litter-amended soil in both time intervals. Therefore, nitrogen mineralization efficiency was decreased to 60% after 180 days compared to that after 90 days in nanoparticles grass-litter amended soil. These effects can be explained by the presence of labile Fe in microbial biomass after 180 days in nanoparticles amendment. Hence, our results suggest that toxicity of IONPs to soil functioning should consider before recommending their use in agro-ecosystems.

Gas Exchange, Chlorophyll Fluorescence and Antioxidants as Bioindicators of Airborne Heavy Metal Pollution in Jeddah, Saudi Arabia

Lettuce (Lactuca sativa L. cv. Romaine) plants were exposed to different levels of urbanization in Jeddah city, Saudi Arabia. They showed different degrees of visible injury symptoms and dramatic changes in enzymatic activities as well as net photosynthetic rates (P N ), variable to maximum chlorophyll fluorescence (Fv /Fm) and stomatal conductance (gs). Visual symptoms of phytotoxicity of heavy metals were observed on plants grown at industrial and urban areas, where the concentrations of metals was about 36 times higher than in other sites. The decrease in chlorophyll reached 70 and 64% in plants cultivated in the industrial and urban regions, while lengths of shoots reduced by 50 and 41% in plants collected from the same locations, respectively. The reduction in chlorophyll and other physiological and biochemical parameters were correlated with the concentrations of airborne pollutants measured in the atmosphere of the locations examined. Moreover, lettuce plants cultivated in the industrial region accumulated more heavy metals than others, which can pass into the human food chain. Photosynthetic efficiency was significantly decreased and lipid peroxidation was enhanced. Antioxidant enzymes were significantly altered during exposure. The biochemical and physiological parameters measured in the present study clearly showed that they could form the basis of a plant biomarkers battery for monitoring and predicting early effects of exposure to airborne heavy metals.

The optical signature of 2,6-bis((E)-2-(benzoxazol-2-yl)vinyl)naphthalene (BBVN) laser dye: a TDDFT study

The photophysical properties of the 2,6-bis((E)-2-(benzoxazol-2-yl)vinyl)naphthalene (BBVN) laser dye have been investigated by time-dependent density functional theory (TDDFT) using the BMK functional in the gas phase and solvents. Upon photon absorption, the dye undergoes an intense ππ* transition polarized along the long molecular axis. The natural transition orbital (NTO) representation of excitation indicates that the benzoxazole nucleus provides a room for a larger charge displacement in absorption/emission. The calculated small value of Stokes shift together with the root-mean-square distance demonstrates that the excited state (S1) geometry is not significantly displaced from that of the ground state (S0). Using a panel of solvation models (LR-PCM, cLR-PCM, and SS-PCM) we have shown that the solvent hardly has an impact on absorption but has a slight positive solvatochromic effect on fluorescence. The calculated E0–0 energy agrees with the experimental absorption-fluorescence crossing point (AFCP). The vibronic band simulation supports the vibronic origin of the measured spectra. Owing to its large oscillator strength, short fluorescence lifetime, high photo-stability and increased rigidity in the excited state, the BBVN dye meets the necessary requirements for being a good laser dye.

Impact of flash flood recharge on groundwater quality and its suitability in the Wadi Baysh Basin, Western Saudi Arabia: an integrated approach

An integrated approach was used to evaluate the impact of flash flood recharge on groundwater quality and its suitability for drinking, irrigation, livestock and poultry uses in the Wadi Baysh Basin, Western Saudi Arabia. Analyses of 182 groundwater samples, collected from the study area before and after a flash flood (FF) event, show that the average concentrations of TDS, Mg, Na, Cl, NO3 and EC decreased significantly after the event. The major water types (mixed CaMgCl, NaCl and CaCl) indicate that the infiltration of surface water from FF recharge has a great influence on groundwater chemistry. Drinking water suitability maps, created using WHO standards, indicate that wells located in the upstream region are suitable for drinking despite their high TDS and total hardness (TH) values. Groundwater in the coastal region is unsuitable due to its high salinity, high TH and high concentrations of major ions. The suitability of groundwater for irrigational use was assessed using salinity, sodium adsorption ratio, bicarbonate hazard, residual sodium carbonate, Kelly’s ratio, magnesium hazard, sodium percentage and permeability index values, which indicated that groundwater in the study region is suitable for most soils and crops. After FF, groundwater quality is improved by dilution, especially in the downstream region. USSL classification shows that the majority of the water samples are in the C3S1, C4S2, and C3S2 classes and are therefore suitable for the irrigation of salt-tolerant crops. Irrigational suitability maps suggest that wells in the upstream region are suitable for irrigation, whereas wells located near to the coast are unfit for irrigation. This study implies that construction of check dams in the dry valleys (wadies) may improve the groundwater quality in the area.

The role of hydrogen bonding in the fluorescence quenching of 2,6-bis((E)-2-(benzoxazol-2-yl)vinyl)naphthalene (BBVN) in methanol

The excited state hydrogen bonding dynamics of BBVN in hydrogen donating methanol solvent was explored at the TD-BMK/cc-pVDZ level of theory with accounting for the bulk environment effects at the polarizable continuum model (PCM). The heteroatoms of the BBVN laser dye form hydrogen bonds with four methanol molecules. In the formed BBVN-(MeOH)4 complex, the A-type hydrogen bond (N…HO), of an average strength of 25kJmol-1, is twofold stronger than the B-type (O…HO) one. Upon photon absorption, the total HB binding energy increases from 78.5kJmol-1 in the ground state to 82.6kJmol-1 in the first singlet (S1) excited state. In consequence of the hydrogen bonding interaction, the absorption band maximum of the BBVN-(MeOH)4 complex, which was anticipated at 398nm (exp. 397), is redshifted by 5nm relative to that of the free dye in methanol. The spectral shift of the stretching vibrational mode for the hydrogen bonded hydroxyl groups (with a maximum shift of 285cm-1) from that of the free methanol indicated the elevated strengthening of hydrogen bonds in the excited state. The vibrational modes associated with hydrogen bonding provide effective accepting modes for the dissipation of the excitation energy, thus, decreasing the fluorescence quantum yield of BBVN in alcohols as compared to that in the polar aprotic solvents. Since there is no sign of photochemistry or phosphorescence, it seems reasonable in view of the outcomes of this study to assign the major decay process of the excited singlet (S1) of BBVN in alcohols to vibronically induced internal conversion (IC) facilitated by hydrogen bonding.