The Role of Silica Nanoparticles in Promoting the Germination of Tomato (Solanum lycopersicum) Seeds.

The addition of nanoparticles has been reported to be an effective strategy for enhancing seed germination, but the underlying mechanisms whereby this occurs are unclear. In the present study, we added silica nanoparticles (SiNPs) to an aqueous growth medium in which tomato seeds were germinated. We examined the effects of SiNPs on growth and possible mechanisms of action. SiNPs had a diameter of 10-17 nm and 110-120 nm. SiNPs shortened the mean germination time from 5.24 ± 0.29 days to 4.64 ± 0.29 days. Seedling vigor, measured by criteria including length and weight, was also improved compared to the control condition. The presence of SiNPs in the seedlings was assessed using an X-ray fluorescence spectrometer. The nanoparticles may have promoted germination by enhancing water imbibition by the seeds or altering the external microenvironment. Scanning electron microscopy revealed changes in the seed coat during germination, many of which were only observed in the presence of nanoparticles. Soil bacteria affect germination; specifically, Bacillus sp. may promote germination. The number of Bacillus sp. changed in the germination medium with SiNPs compared to the control. This suggested that these bacteria could interact with SiNPs to promote germination.

Effect of enhanced CaCl2, MgSO4, and KH2PO4 on improved in vitro growth of potato.

Potato (Solanum tuberosum L.) is a major global food crop. Contemporary potato production largely utilizes micropropagation to produce healthy seed potatoes. The micropropagation of potatoes is widely achieved through nodal explants using the conventional Murashige and Skoog (MS) medium. Currently, effective culture media that can facilitate rapid propagation are increasingly required for new cultivars that have been developed to possess improved traits. In this study, we evaluated the effect of enhanced meso nutrients (CaCl2.2H2O, MgSO4, and KH2PO4) in MS medium on the growth of S. tuberosum. The cultivars used in this study were representative of Japanese, European, and Peruvian lines. Enhanced meso nutrients improved the overall quality of all cultivars, as indicated by longer shoots and larger leaves with dark color, compared with MS medium only. Shoots grown on enhanced mesos were approximately 1.5 times longer than on MS medium. Quantitative ion analysis revealed that plantlets with improved shoot length and leaf quality in most cultivars had increased calcium, magnesium, potassium, and phosphorus uptake than plantlets on MS medium. The results suggest that the reduced iron uptake on 3.0×MS, compared with 2.0× or 2.5×MS mesos, reduced plant growth. This study revealed for the first time that mesos concentrations higher than MS medium concentrations, complemented by enhanced calcium, magnesium, potassium, phosphorus, and iron uptake, play a significant role in improving the in vitro growth of potato.

Propagation of Polygonatum macranthum (Maxim.) Koidz. from immature seeds using a new sterilization procedure.

Natural seed germination is difficult to achieve in numerous plant species of wide economic importance. The germination of Polygonatum macranthum seeds takes as long as one and a half years under natural conditions. In addition, propagation by rhizome is also extremely slow in this species. Therefore, the natural propagation of P. macranthum through seeds or rhizome is not efficient. In this study, an efficient in vitro propagation system for P. macranthum from immature seeds with seed coat was developed, using a new surface sterilization protocol that utilized a low concentration of hypochlorite. In vitro germination was achieved at a rate of 30% within 9 weeks after inoculation on 1/2 MS medium. Shoot explants from seedlings were successfully cultured on 1/2 MS medium. Supplementation of the 1/2 MS medium with cytokinin 6-benzylaminopurine (BAP) facilitated efficient propagation by microrhizome. An efficient propagation rate of 1.3 microrhizomes per shoot in an 8-week culture period could be achieved by using a concentration of 1 mg l-1 BAP. During 4 weeks of acclimatization, 88% of shoots were rooted and started to grow into juvenile plants. After about 16 weeks in the field, 13% of the acclimatized plants showed viable growth and healthy regenerating shoots. The cultivation system demonstrated in this study can be used to propagate P. macranthum.

A nitrogen removal system to limit water exchange for recirculating freshwater aquarium using DHS-USB reactor.

This study proposes a biological nitrogen removal system for freshwater aquaria consisting of a down-flow hanging sponge (DHS) and an up-flow sludge blanket (USB). DHS-USB systems can perform nitrification and denitrification simultaneously, reducing ammonia (NH3) and nitrate (NO3-) toxicity in the water. The performance of the system was evaluated using on-site fresh water aquaria at ambient temperature (23-34°C) over 192 days. NH3 and nitrite (NO2-) were maintained at a detection limit of 0.01 mg N L-1 and NO3- was maintained below 10 mg N L-1, despite limited water exchange. The 16S rRNA gene of microorganisms from the sludge retained in the bioreactors was sequenced to identify the microbial communities present. Microbial community analysis revealed that ammonia oxidizing archaea (AOA), Ca. Nitrososphaera and Nitrosopumilus, played an important role in nitrification in the DHS reactor, while denitrifying bacteria Thauera played an important role in denitrification in the USB reactor. The proposed DHS-USB system is a promising technological advancement in the development of lower maintenance aquaria.

Cryopreservation of blueberry shoot tips derived from in vitro and current shoots using D cryo-plate technique.

Cryopreservation is an important tool for long-term storage of plant germplasm that is currently used for plant germplasm storage at many institutes worldwide. Recently, novel cryogenic procedures (V and D cryo-plate methods) have been developed. In this study, the most suitable conditions for preserving blueberry shoot tips derived from in vitro and current shoots using the D cryo-plate method were investigated. The D cryo-plate method has advantages such as higher regrowth after cryopreservation and a more user-friendly process compared with conventional cryogenic methods. The optimum duration of desiccation for regrowth of shoot tips from each shoot type was 1 h. To induce dehydration tolerance for the shoot tips, the effects of two cryoprotection treatments (sucrose preculture and loading solution [LS] treatment) on shoot regrowth after cryopreservation were investigated. The combined effect of both treatments significantly increased percentage regrowth (approximately 90%). No regrowth of shoot tips was attained without the two treatments. Thus, preculture and LS treatment were effective to induce dehydration tolerance for cryopreservation of blueberry shoot tips. The optimized conditions for blueberry shoot tips using the D cryo-plate technique were: preculture with 0.3 M sucrose for 1 day, LS treatment (2 M glycerol +0.4-1.0 M sucrose) for 30 min, and air dehydration for 1 h. This optimized procedure was applied to additional blueberry cultivars shoot tips derived from in vitro shoots (regrowth 46.7-100%) and current shoots (regrowth 17.2-62.7%). Furthermore, in vitro shoot tips were suitable material for the D cryo-plate method in blueberry.

Genetic stability assessment of wWasabi plants regenerated from long-term cryopreserved shoot tips using morphological, biochemical and molecular analysis.

This study compared the effect of cryopreserved storage duration of wasabi shoot tips, which derived from the same in vitro mother-plant. We compared the survival of shoot tips and the genetic stability of regenerated plants originating from four experimental groups: shoot tips stored in a -150°C deep-freezer for 10 years; shoot tips stored in liquid nitrogen for 2 h; shoot tips treated with PVS2 vitrification solution; and untreated controls. No significant difference in survival was observed between the four experimental groups. Survival ranged between 93 and 100%. Genetic stability of plants regenerated from cryopreserved shoot tips was assessed over a period of 24 months using morphological, biochemical and molecular markers. While glucose, fructose and glutamic acid concentrations differed slightly between experimental groups after 16 months, these differences disappeared after 24 months. No significant differences were noted for the morphological markers studied (petiole length, shoot number and leaf index). No differences were observed in RAPD profiles obtained with the six primers tested.