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Using nanofertilizers in certain concentrations can be a novel method to alleviate drought stress effects in plants as a global climate problem. We aimed to determine the impacts of zinc nanoparticles (ZnO-N) and zinc sulfate (ZnSO 4 ) fertilizers on the improvement of drought tolerance in Dracocephalum kotschyi as a medicinal-ornamental plant. Plants were treated with three doses of ZnO-N and ZnSO 4 (0, 10, and 20 mg/l) under two levels of drought stress [50% and 100% field capacity (FC)]. Relative water content (RWC), electrolyte conductivity (EC), chlorophyll, sugar, proline, protein, superoxide dismutase (SOD), polyphenol oxidase (PPO) and, guaiacol peroxidase (GPO) were measured. Moreover, the concentration of some elements interacting with Zn was reported using the SEM-EDX method. Results indicated that foliar fertilization of D. kotschyi under drought stress with ZnO-N decreased EC, while ZnSO 4 application was less effective. Moreover, sugar and proline content as well as activity of SOD and GPO (and to some extent PPO) in treated plants by 50% FC, increased under the influence of ZnO-N. ZnSO 4 application could increase chlorophyll and protein content and PPO activity in this plant under drought stress. Based on the results, ZnO-N and then ZnSO 4 improved the drought tolerance of D. kotschyi through their positive effects on physiological and biochemical attributes changing the concentration of Zn, P, Cu, and Fe. Accordingly, due to the increased sugar and proline content and also antioxidant enzyme activity (SOD, GPO, and to some extent PPO) on enhancing drought tolerance in this plant, ZnO-N fertilization is advisable.

Background The use of organic nanoparticles to improve drought resistance and water demand characteristics in plants seems to be a promising eco-friendly strategy for water resource management in arid and semi-arid areas. This study aimed to investigate the effect of chitosan nanoparticles (CNPs) (0, 30, 60 and 90 ppm) on some physiological, biochemical, and anatomical responses of Salvia abrotanoides under multiple irrigation regimes (30% (severe), 50% (medium) and 100% (control) field capacity). Results The results showed that drought stress decreases almost all biochemical parameters. However, foliar application of CNPs mitigated the effects caused by drought stress. This elicitor decreased electrolyte conductivity (35%), but improved relative water content (12.65%), total chlorophyll (63%), carotenoids (68%), phenol (23.1%), flavonoid (36.4%), soluble sugar (58%), proline (49%), protein (45.2%) in S. abrotanoides plants compared to the control (CNPs = 0). Furthermore, the activity of antioxidant enzymes superoxide dismutase (86%), polyphenol oxidase (72.8%), and guaiacol peroxidase (75.7%) were enhanced after CNPs treatment to reduce the effects of water deficit. Also, the CNPs led to an increase in stomatal density (5.2 and 6.6%) while decreasing stomatal aperture size (50 and 25%) and semi-closed stomata (26 and 53%) in leaves. Conclusion The findings show that CNPs not only can considerably reduce water requirement of S. abrotanoides but also are able to enhance the drought tolerance ability of this plant particularly in drought-prone areas. Graphical abstract Highlights • Foliar application of CNPs can improves drought tolerance. • Leaves showed a high antioxidant enzyme activity under drought stress using CNPs. • Biochemicals varied by drought stress levels and CNPs concentrations. • The highest and the lowest stomatal density and aperture size, respectively were observed in the plants treated with CNPs under drought stress.

Carbon nanomaterials such as single-walled carbon nanotubes (SWCNTs) offer a new possibility for phyto-nanotechnology and biotechnology to improve the quality and quantity of secondary metabolites in vitro . The current study aimed to determine the SWCNTs effects on Thyme (Thymus daenensis celak.) seed germination. The seedlings were further assessed in terms of morphological and phytochemical properties. Sterile seeds were cultured in vitro and treated with various concentrations of SWCNTs. Biochemical analyses were designed on seedling sample extracts for measuring antioxidant activities (AA), total flavonoids (TFC) and phenolic contents, and the main enzymes involved in oxidative reactions under experimental treatments. The results indicated that an increase in SWCNTs concentration can enhance the total percentage of seed germination. The improvement was observed in samples that received SWCNTs levels of up to 125 µg ml −1 , even though seedling height and biomass accumulation decreased. Seedling growth parameters in the control samples were higher than those of grown in SWCNT-fortified media. This may have happened because of more oxidative damage as well as a rise in POD and PPO activities in tissues. Additionally, secondary metabolites and relevant enzyme activities showed that maximum amounts of TPC, TFC, AA and the highest PAL enzyme activity were detected in samples exposed to 62.5 µg ml −1 SWCNTs. Our findings reveal that SWCNTs in a concentration-dependent manner has different effects on T. daenensis morphological and phytochemical properties. Microscopic images analysis revealed that SWCNTs pierce cell walls, enter the plant cells and agglomerate in the cellular cytoplasm and cell walls. The findings provide insights into the regulatory mechanisms of SWCNTs on T. daenensis growth, germination and secondary metabolites production.

Nanoelicitors are biological and non-biological factors that can affect the synthesis of secondary metabolites in medicinal plants. Feverfew is a valuable medicinal plant containing effective and important anti-cancer compounds (essential oil and parthenolide). This study was conducted to investigate the effects of zinc oxide nanoparticles (ZnONPs) on yield, metabolites content, and zinc and iron absorption of Feverfew. After seed preparation, seedling production, soil physicochemical properties analysis, ZnONPs treatments, maintenance and harvesting at full flowering stage, morphological traits and yield components were measured. The essential oil was extracted by Clevenger and parthenolide was identified by UPLC-MRM-MS. The content of Zn and Fe were measured by OES-ICP. The effects of ZnONPs were significant on all morpho-phytochemical traits. An increased biological yield (dry weight) was observed at 2000 ppm ZnONPs (32.54 g/day) compared to control (28.09 g/day). The highest (0.9% V/W) and lowest (0.56% V/W) content of essential oil were related to 1000 ppm ZnONPs and control. The content of parthenolide decreased at different levels of ZnONPs. The lowest (36.83 mg/kg DW) and highest (266.02 mg/kg DW) rates of Zn absorption were observed in control and 2000 ppm ZnONPs. Nanoparticles at all concentrations increased the biological yield, essential oil content, and Zn absorption. None of the ZnONPs concentrations improved the flower yield. Along with increasing ZnONPs and Zn uptake, parthenolide levels decreased. Also, it was determined that there was an antagonistic effect between Zn and Fe absorption.

With the rising demand for new cultivars of carnation, efficient transformation protocols are needed to enable the bioengineering of new traits. Here, we established a novel and efficient Agrobacterium -mediated transformation system using callus as the target explant for four commercial carnation cultivars. Leaf-derived calli of all cultivars were inoculated with Agrobacterium tumefaciens strain LBA4404 containing the plasmid pCAMBIA 2301 harboring genes for β-glucuronidase ( uidA ) and neomycin phosphotransferase ( npt II). Polymerase chain reaction (PCR) and histochemical assays confirmed the presence of uidA and β-glucuronidase (GUS), respectively in transgenic shoots. The effect on transformation efficiency of medium composition and the presence of antioxidants during inoculation and co-cultivation was investigated. The transformation efficiency was increased in Murashige and Skoog (MS) medium lacking KNO 3 and NH 4 NO 3, and also in MS medium lacking macro and micro elements and Fe to 5% and 3.1% respectively, compared to 0.6% in full-strength medium. Transformation efficiency was increased dramatically to 24.4% across all carnation cultivars by the addition of 2 mg/l melatonin to nitrogen-depleted MS medium. Shoot regeneration was also doubled in this treatment. The establishment of this efficient and reliable transformation protocol can advance the development of novel carnation cultivars through molecular breeding approaches. Highlights Melatonin at 2 mg/l substantially increases the Agrobacterium -mediated transformation efficiency of carnation cultivars to 24%. Nitrogen-depleted inoculation and co-cultivation media can greatly enhance carnation transformation. Callus is a potential target explant for Agrobacterium transformation of carnation. Melatonin and lipoic acid can considerably promote the shoot regeneration from transformed callus. The established protocol for carnation transformation is cultivar independent.

The production of valuable bioactive compounds in the medicinal plant Glycyrrhiza glabra L. (G. glabra) would benefit from biotechnological approaches for the cultivation and induction of metabolite-producing hairy roots. Germination trials were tested to overcome seed dormancy, achieving high germination rates with sulfuric acid treatment. Hairy root cultures of cotyledons using Rhizobium rhizogenes strain 1724 showed the highest transformation efficiency. A fast-growing line, line S, was subsequently exposed to light treatments (red, blue, and blue and red combined) to evaluate their effects on growth, phenolic content, and Ferric Reducing Antioxidant Power (FRAP). Hairy root cultures grown in blue light and in blue and red light combined had higher growth rates than those grown in red light only or in control conditions (dark). FRAP increased over time under all light treatments, including the control, and those cultures exposed to blue and red light combined had higher FRAP than the control. These findings provide valuable insights into conditions for optimal seed germination and hairy root transformation. Treatment of the line S with different qualities of light induced changes in antioxidant capacity and phenolic content, indicating promise for its use in upregulating secondary metabolite production in G. glabra for future biotechnological applications.

Iranian seedless barberry is a very recalcitrant species in in vitro culture which does not show appropriate growth on standard culture media. Response surface methodology was employed to evaluate the effects of changing macronutrients concentrations on establishment and proliferation phases. KNO3 and NH4NO3 macronutrients at 0.3 to 1.5 × MS medium levels and CaCl2, MgSO4 and KH2PO4 macronutrients in a range of 0.5 to 1.5 × MS medium concentrations were tested in a response surface design with 30 treatments. Many significant interactions were found among the macronutrients. High concentrations of KNO3, NH4NO3 and CaCl2 improved the growth rate in the establishment phase. The growth rate in media containing high KNO3 and low CaCl2 was high. Reduced concentrations of CaCl2 and KNO3 decreased hyperhydricity. The greatest hyperhydricity was induced when both NH4NO3 and CaCl2 were used at 1.5 × MS level. The number of hooked leaves decreased as KH2PO4 increased and MgSO4 reduced. In the proliferation phase, there were many significant interactions among the macronutrients. Increased concentration of NH4NO3 and reduced concentration of KH2PO4 improved the growth rate. Proliferation rate increased in media containing high concentration of KNO3 and low to moderate concentrations of NH4NO3. The greatest production of new tissues and organs was seen in media with high KNO3 and moderate to high CaCl2. High concentration of NH4NO3 and low concentration of KH2PO4 also increased production of new tissues and organs. No shoot apical meristem was seen when CaCl2 level was high and KNO3 level was low. Formation of shoot apical meristem required high KH2PO4 concentration and low CaCl2 concentration. Finally, low concentration of KNO3 and low to moderate concentrations of NH4NO3 increased phenol exudation.Key messageEstablishment and proliferation phases of Iranian seedless barberry were improved, for the first time, by manipulation of five macronutrients of MS basal medium using Response Surface Methodology.

Rosa canina is one of the most popular rose species which is widely used as the rootstock for the propagation of rose cultivars. The purpose of the present study is to improve the in vitro propagation efficiency of this valuable plant species using various growth stimulants in a proliferation medium. In this study, in vitro-derived axillary buds of R. canina were inoculated in Vander Salm (VS) medium supplemented with varying levels of organic or inorganic elicitors including casein hydrolysate (200, 400, and 600 mg/l), glutamic acid (2, 4, 8, and 12 mg/l), proline (500, 1000, 1500, and 2000 mg/l), and silver nitrate (25, 50, 75, and 100 mg/l), separately. Benzyl amino purine (BAP) as well as naphthalin acetic acid (NAA) were added to all media at a constant rate to promote shoot proliferation. The results indicated that the supplementation of casein hydrolysate to the VS medium markedly stimulated shoot regeneration by 173% in comparison to control. Shoot proliferation was also positively influenced by glutamic acid at all levels, however, at a lesser extent compared to casein hydrolysate. Silver nitrate at 100 mg/l induced the longest shoots (2.52 ± 0.248 cm) and maximum leaf number (8.90 ± 0.276) among all treatments. Although it did not encourage efficient shoot regeneration, the highest quality shoots with maximum growth vigor were observed in this treatment. In this study, the promising role of casein hydrolysate in combination with plant growth regulators has been emphasized for the improved efficiency of R. canina regeneration protocol. Moreover, the addition of silver nitrate to the culture medium seems vital for enhancing the quality of regenerated shoots. The results of this study could be beneficial either for the further pharmaceutical or biochemical investigations of R. canina or commercial purposes for mass propagation of this specimen.

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Tissue culture and micrografting techniques are known as effective procedures to produce healthy rose rootstocks and high quality scions. In order to establish successful micrografting protocol for roses, several factors including different concentrations of Benzylamino-purine (BA) (0, 1, 1.5, 2 mg l −1 ) + 0.1 mg l −1 α-Naphthaleneacetic acid (NAA), sucrose concentrations (30, 50, 70 g l −1 ), types of grafting devices (aluminium foil, parafilm, paper bridge), and types of rose scions cultivars ( Rosa hybrida cv. Red One, R. hybrida cv. Samurai) on two different types of native ( Rosa canina ) and commercial rose rootstocks ( Rosa multiflora cv. Natal Briar) were examined. The high micrografting success (100%) was micrografting R. hybrida cv. Samurai scion on R. mutiflora cv. Natal Briar rootstock with the paper bridge as the best grafting device in the liquid Van der salm (VS) medium containing 2 mg l −1 BA + 0.1 mg l −1 NAA + 300 mg l −1 Casein Hydrolyzate + 2 g l −1 myo-inositol + 50 g l −1 sucrose. Treating the wounded explants (scions and rootstocks) with silver nitrate (50 mg l −1 ) during the micrografting process, increased the survival of micrografts. The micrografted plants were successfully rooted and well acclimatized. The present results provide the first efficient protocol to produce high successful micrografted rose plantlets in tissue culture. Key message It is the first research protocol for micrografting of native and commercial roses by considering important factors relating to successful micrografting such as plant growth regulators, growth adjuvants, grafting devices, and medium ingredients.