A detailed study was performed on unirradiated low-and high-density polyethylene (LDPE and HDPE) films as well as irradiated films with different types of radiation such as 60 Co ␥ rays, thermal and fast neutrons, and electron beam irradiation. The structural changes of PE films were characterized by Fourier transform infrared (FTIR), Fourier transform Raman (FT-Raman), and ultraviolet (UV) spectrometric techniques. The results showed significant radiation degradation, crosslinking, and changes in the crystalline and amorphous regions. The influence of ␥-radiation on the structure of PE was found to be more prominent compared to that of thermal neutrons and electron beam irradiation. However, LDPE film was found to be more sensitive to these types of radiation in accordance with HDPE because of its lesser degree of crystallinity.

T HE PRESENT study investigated the synthesis of silver nanoparticles (AgNPs) using Capparis spinosa extract as reducing and stabilizing agent. The biosynthesized AgNPs were characterized by UV-vis spectrophotometer and energy dispersive spectroscopy (EDS) analysis. The shape and size of the biosynthesized AgNPs were studied using transmission electron microscope (TEM). The study also investigated whether the biosynthesized AgNPs (as a priming agent; 1 mg L-1) has a role in the alleviation of the salt-induced toxicity of germinating Triticum aestivum L. grains grown under salt stress (25 and 100 mM NaCl). Generally, AgNPs priming stimulate the germination and growth of wheat grains. In addition, it affects the plant phytohormones balance by stimulating indole-3-butyric acid (IBA), 1-naphthalene acetic acid (NAA), 6-benzylaminopurine (BAP) contents and reducing abscicic acid (ABA) content. Slat stress had an inhibitory effect on wheat seedling as evident by a significant decrease in GP, growth index, pigment contents and chlorophyll stability index (CSI), auxins and cytokinins contents and a marked increase in ABA content particularly at 100 mM NaCl. All these parameters were markedly improved by AgNPs priming notably growth parameters and photosynthetic efficiency as well phtyohormones balance suggesting that AgNPs priming might has a role in the improvement of plant tolerance against environmental stresses such as salinity.

A detailed study was performed on unirradiated low-and high-density polyethylene (LDPE and HDPE) films as well as irradiated films with different types of radiation such as 60 Co ␥ rays, thermal and fast neutrons, and electron beam irradiation. The structural changes of PE films were characterized by Fourier transform infrared (FTIR), Fourier transform Raman (FT-Raman), and ultraviolet (UV) spectrometric techniques. The results showed significant radiation degradation, crosslinking, and changes in the crystalline and amorphous regions. The influence of ␥-radiation on the structure of PE was found to be more prominent compared to that of thermal neutrons and electron beam irradiation. However, LDPE film was found to be more sensitive to these types of radiation in accordance with HDPE because of its lesser degree of crystallinity.

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Various physiological damages occur in plants upon exposure to heat stress (Hasanuzzaman et al. 2013). High temperatures (heat stress, HS) are known to inhibit enzyme activity, net photosynthetic rate (P N ), and other metabolic processes leading to physiological and biochemical alterations (Salvucci and Crafts-Brander 2004, Hassan, 2006, Zhao et al. 2008, ICPP 2014. HS uncouples enzymes and metabolic pathways leading to accumulation of harmful reactive oxygen species (ROS) which are responsible for oxidative stress (Sarieva et al. 2010). The reaction centers of PSI and PSII in chloroplasts are major sites of ROS generation (Chakraborty et al. 2011). Stomatal closure, reduction in root growth, and consequent inhibition of mineral uptake are common responses to HS (Huang and Xu 2000).Nitrogen as an essential element (Sánchez et al. 2004, Cechin and De Terezinha 2004) promotes metabolic activities, such as photosynthesis, antioxidant activities, leading to enhancing in growth and yield (Zhao et al. 2008).Due to their different physiological effects, HS and N fertilization might have interactive impacts on plants. HS reduces the rate of nutrient uptake; however, this effect could be mitigated by excessive supply of N (Altenbach et al. 2003, Zhao et al. 2008, Demmig-Adams et al. 2014. Moreover, Zhang et al. (2014) reported that N nutrition control is an important way to enhance tolerance to abiotic stress. Thus, it is important to understand how the supply of N may mitigate HS.The aim of the present experiment was to study the effects of N-fertilization on alleviation of the negative impact of HS on Chl fluorescence, P N , and stomatal conductance (g s ) of French bean plants.Seeds of French bean (Phaseolus vulgaris L.) were obtained from the Department of Agronomy, Alexandria University, Egypt. They were sown in plastic pots (20 cm 2 ), five seeds in each pot with multipurpose compost in a heated glasshouse [temperature of 24/20ºC day/night, air humidity 60-65%, 16-h photoperiod with additional irradiance of 450 μmol(photon) m -2 s -1 , total irradiance was 975 μmol(photon) m -2 s -1 ]. After appearance of expanded trifoliate leaf, 12 days after sowing (DAS), plants were thinned to one seedling per pot. Pots were then transferred to eight closed climate controlled growth chambers. Two chambers were used for N fertilization as foliar spray (three concentrations of urea: 5, 10, 15 mM). Two other