Microbial contaminants are the major challenges in plant's in vitro propagation during different stages of culture processes, ZnO-NPs exhibit attractive antibacterial properties due to increased specific surface area as the reduced particle size leading to enhanced particle surface reactivity. The aim of present study was to evaluate the effect of ZnO NPs on microbial contamination; vitrification and growth promoting of date palm cultured tissues. Several concentrations of ZnO NPs were selected to assess their activity. The percentage of shoot formation, the number of proliferated shoot and the percentage of contamination of cultures were investigated, as well as several biochemical characteristics. Twofold of increase multiplication rate of proliferated shoot was observed in ZnO NPs at 150 mg L −1 compared to control treatment. The multiplication rate was 46.6% at control and increased significantly to 86.67% and 93.34% in ZnO NPs before and after sterilisation, respectively. No microbial contamination and vitrification were observed at all ZnO NP treatments compared with control treatment. Biochemical analysis showed that ZnO NPs had no toxic effects at all examined concentrations on date palm cultured tissues. A positive effect was observed in carbohydrates, protein and amino acid accumulations at high ZnO concentration (150 mg l −1). The results provide basis for the application of ZnO NPs in media date palm tissue cultures at 150 mg l −1 .

BackgroundAl is a common metallic element found in earth's crust and is a toxic pollutant present at high concentrations in acidic soil, thus affecting plant growth. Despite being well studied as a toxic element, the effects of Al on date palm have not been investigated. This study aimed to assess the toxic effects of different Al concentrations on the development and growth of date palm callus and evaluate the biochemical and molecular response of date palm cells under Al stress.ResultsOur study revealed the phytotoxicity of Al concentrations (50, 100, 150 and 200 mg.l-1) on date palm callus. The fresh and dry weight and the number of produced embryos were significantly decreased in response to Al concentration. At 150 mg.l-1, the embryo number decreased to 1.66 compared with the 19.33 in the control treatment. At high Al concentration (200 mg.l-1), the callus failed to produce any embryo. Biochemical analysis revealed that Al exposure had negative effect on callus. Total soluble carbohydrates, total soluble protein and free amino acids were decreased in plants receiving 200 mg.l-1 Al treatment compared with those in the untreated ones. A similar decline was observed in total soluble protein and free amino acid in response to Al treatment. Significant accumulations of malondialdehyde, H2O2 and peroxidase activity accompanied the increase in Al concentration in cultured tissues, revealing the generation of toxic reactive oxygen species in affected cultures. The genotoxic effect of Al at high concentrations (150 and 200 mg.l-1) was revealed by protein patterns.ConclusionOur findings revealed for the first time the phytotoxicity of Al to date palm callus. At 200 mg.l-1, Al prevented the embryo production of date palm callus. At 50, 100, 150 and 200 mg.l-1, Al negatively affected the biochemical characteristics of date palm callus. At 150 and 200 mg.l-1, Al induced changes in protein expression. These data showed that the tissue culture technique can be used as a valuable approach in heavy metal toxicity studies.

The current study used the Fourier Transform Infrared (FTIR) spectroscopy to determine the corresponding changes caused by salt-induced biochemical changes at different NaCl concentrations (2.5 as control level, 5, 10, and 20 ds.m − 1 ). FTIR also determines the potential role of selenium nanoparticles (Se NPs) at two concentrations (80 and 160 ppm) in alleviating salinity stress on date palm (Phoenix dactylifera L.) trees. Notably, the study found the appearance of a new peak at 2850 cm − 1 in the lipid region (2800-3000 cm − 1 ) when date palm trees were exposed to salinity and tested at all levels. This peak was not seen in the control treatment or when salinity was combined with foliar spraying of Se NPs at the two tested concentrations (80 and 160 ppm). Furthermore, a clear and distinct peak at 1735 cm − 1 was only seen in plants exposed to salinity at 10 or 20 ds.m − 1 . This peak was attributed to membrane lipid compounds that contain carbonyl-ester groups. In addition, the ndings demonstrate that the treatments from various studies affected the secondary structure of proteins (1500-1800 cm − 1 ) and carbohydrates (1200-1500 cm − 1 ), and this was evident by the appearance and disappearance of some characteristic peaks in these regions.

This study investigated the effect of salinity on the anatomical features of date palm (Phoenix dactylifera L.) and the potential roles of nano selenium (Se NPs) in alleviating the adverse effects of salinity. Two concentrations (80 and 160 mg.L-1) of SeNPs were applied as a foliar spray on date palms irrigated with different concentrations of saline water (2.5 [control], 5, 10 and 20 ds.m-1). Results showed that 5 ds.m-1 salinity had no significant effect on the anatomical structure of date palm, whether applied alone or in combination with foliar spray of Se NPs. However, the vascular bundle dimensions and thickness of the xylem, phloem and mesophyll were significantly higher in plants exposed to 10 ds.m-1 salinity compared with the control plants. In particular, foliar spray of SeNPs at 80 mg.L-1 concentration enhanced the effect on these plants. By contrast, 20 ds.m-1 salinity significantly reduced all studied parameters except for the thickness of the upper and lower cuticle, which increased. Se NPs at 80 mg.L-1 concentration had a significant effect in alleviating the adverse effects of salinity at high levels. The results of this study proved that SeNPs at 80 mg.L-1 concentration were more effective in alleviating the adverse effects of salinity on the anatomical structure of date palm leaves than 160 mg.L-1 concentration.

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