Engineered nanomaterials have increased for their positive impact in improving many sectors of economy including agriculture. Silver nanoparticles (AgNPs) have been implicated nowadays to enhance seed germination, plant growth, improvement of photosynthetic quantum efficiency and as antimicrobial agents to manage plant diseases. In this study, we examined effect of AgNPs dosage on seed germination of three plant species; corn (Zea mays L.), watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) and zucchini (Cucurbita pepo L.). Therefore, this experiment designed to study the effect of AgNPs on germination percentage, germination rate, mean germination time, root length, fresh and dry weight of seedling for the three spices. Seven concentrations (0.05, 0.1, 0.5, 1, 1.5, 2 and 2.5 mg/L) of AgNPs were examined at seed germination stage. The results showed that the three spices revealed different dosage response to AgNPs on germination percentage and the measured growth characters. Germination rate values were enhanced for the three plants in response to AgNPs. Significant enhancement in germination percentage values for watermelon and zucchini plants were observed by treatment with AgNPs in comparison with nontreated seeds. AgNPs showed toxic effect on corn roots elongation whereas watermelon and zucchini seedling growth were positively affected by certain concentration of AgNPs. This study showed that exposure to AgNPs caused both positive and negative effects on plant growth and germination.

To cite this paper: Almutairi, Z.M., 2016. Influence of silver nano-particles on the salt resistance of tomato (Solanum lycopersicum) during germination. AbstractSilver nanoparticles (AgNPs) have been implicated to enhance seed germination and plant growth, improve photosynthetic quantum efficiency and act as antimicrobial agents to manage plant diseases. The role of nanoparticles in the improvement of plant tolerance to environmental stresses such as drought and salinity remains unclear. In this study, we examined the effects of AgNP dose on the salt tolerance of tomato (Solanum lycopersicum L.) plants during germination. Tomato seeds were treated with different AgNP doses and germinated under salinity stress. Five concentrations of AgNPs (0.05, 0.5, 1.5, 2 and 2.5 mg L -1 ) and two levels of NaCl (150 and 100 mM) were tested. Seed germination and seedling growth of tomato plants were markedly inhibited by salt stress, and this effect was alleviated by exposure to AgNPs. The germination percentage, germination rate, root length and seedling fresh and dry weight of tomato were improved after exposure to AgNPs under NaCl stress. The expression of salt stress genes was investigated by semi-quantitative RT-PCR. Of the examined salt stress genes, four genes, AREB, MAPK2, P5CS and CRK1, were up-regulated by AgNPs under salt stress, and three genes, TAS14, DDF2 and ZFHD1, were down-regulated in response to AgNPs. The gene expression patterns associated with AgNP exposure also suggest the potential involvement of AgNPs in response to stress, indicating that they might be useful for improving plant tolerance to salinity.

VERNALIZATION INSENSITIVE 3 (VIN3) is a chromatin remodelling protein that is induced by low temperatures and is required for the vernalization response in Arabidopsis thaliana. VIN3 is one of the polycomb group (PcG) proteins, which mediates epigenetic repression of FLOWERING LOCUS C (FLC) in A. thaliana. Here, we present cloning, characterization, and expression of a putative SlVIN3 gene in tomato (Solanum lycopersicum L.) by isolating cDNA clones corresponding to SlVIN3 gene using primers designed based on conserved sequences between PcG genes in A. thaliana and tomato. The SlVIN3 cDNAs were cloned into a pBS plasmid and sequenced. Both 5' and 3' RACE were generated and sequenced. The flcDNA of 2 823 bp length for the SlVIN3 gene was composed of 5'UTR (336 bp), ORF (2 217 bp), and 3'UTR (270 bp). The translated ORF encoded a polypeptide of 739 amino acids. Alignment of deduced amino acids indicates that there are highly conserved regions between tomato SlVIN3 predicted protein and plant VIN3 gene family members. Both unrooted phylogenetic trees constructed using the maximum parsimony and maximum likelihood methods indicate that there is a close relationship between SlVIN3 predicted protein and VIN3 protein of Vitis vinifera. The expression of SlVIN3 gene remained high during floral organ differentiation and growth and decreased when the fruit started to develop.

Local cultivars of pearl millet in Saudi Arabia are known to tolerate extreme heat and drought stress. In the current study, the sequences of internal-transcribed spacers (ITSs) of six pearl millet cultivars were sequenced and analysed to investigate the genetic diversity among the local cultivars. The nucleotide polymorphism, secondary structures and phylogenetics were analysed for ITS sequences of the six local cultivars. The obtained sequences were 772–774 base pairs (bp) in length, including complete sequences of the ITS1–5.8S–ITS2 region and partial sequences of 18S and 26S rRNA. The nucleotide diversity among cultivars was higher in ITS2 sequences than ITS1 sequences. The ITS2 had four variable nucleotide sites in three native cultivars, whereas the ITS1 contained one base insertion. The secondary structures of the ITS1 and 5.8S region were highly conserved among the six cultivars and contained some motifs that are conserved across Viridiplantae. However, the ITS2 secondary structure for the two native cultivars, Sayah and Jazan, was distinct from the other cultivars, which confirms the applicability of the ITS2 sequence in distinguishing between genetically close taxa. Additionally, the phylogenetic analysis of the six investigated cultivars and 31 pearl millet accessions from the NCBI database showed close relationships between the local accessions and NCBI accessions from India and France. However, the local cultivar Sayah appeared to be distinct from the other cultivars in the phylogenetic trees. This study provides insights into the polymorphism within local pearl millet cultivars which is important for the identification and conservation of these cultivars.

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