Transcriptomic profiling of the high-vigour maize (Zea mays L.) hybrid variety response to cold and drought stresses during seed germination

Abiotic stresses, including cold and drought, negatively affect maize (Zea mays L.) seed field emergence and later yield and quality. In order to reveal the molecular mechanism of maize seed resistance to abiotic stress at seed germination, the global transcriptome of high- vigour variety Zhongdi175 exposed to cold- and drought- stress was analyzed by RNA-seq. In the comparison between the control and different stressed sample, 12,299 differentially expressed genes (DEGs) were detected, of which 9605 and 7837 DEGs were identified under cold- and drought- stress, respectively. Functional annotation analysis suggested that stress response mediated by the pathways involving ribosome, phenylpropanoid biosynthesis and biosynthesis of secondary metabolites, among others. Of the obtained DEGs (12,299), 5,143 genes are common to cold- and drought- stress, at least 2248 TFs in 56 TF families were identified that are involved in cold and/or drought treatments during seed germination, including bHLH, NAC, MYB and WRKY families, which suggested that common mechanisms may be originated during maize seed germination in response to different abiotic stresses. This study will provide a better understanding of the molecular mechanism of response to abiotic stress during maize seed germination, and could be useful for cultivar improvement and breeding of high vigour maize cultivars.

Reasons Why Geomagnetic Field Generation is Physically Impossible in Earth’s Fluid Core

Despite the importance for understanding the nature of the geomagnetic field, and especially its potential for radically disrupting modern civilization [1], virtually all scientific publications relating to it are based upon the false assumption that the geomagnetic field is generated in the Earth’s fluid core. By adhering to an outmoded paradigm, members of the geoscience community have potentially exposed humanity to globally devastating risks, leaving it unprepared for an inevitable geomagnetic field collapse. There is no scientific reason to believe that the geomagnetic field is generated within the fluid core. Convection is physically impossible in the fluid core due to its compression by the weight above and its inability to sustain an adverse temperature gradient. There is no evidence of ongoing inner core growth to provide energy to drive thermal convection or to cause compositional convection. Moreover, there is no mechanism to account for magnetic reversals and no means for magnetic seed-field production within the fluid core to initiate dynamo amplification. Earth’s nuclear georeactor, seat of the geomagnetic field, has none of the problems inherent in putative fluid-core geomagnetic field production. With a mass of about one ten-millionth that of the fluid core, georeactor sub-shell convection can potentially be disrupted by great planetary trauma, such as an asteroid impact, or by major solar outbursts or even by human activities, for example, by deliberate electromagnetic disturbance of the near-Earth environment, including the Van Allen belts. Furthermore, sub-shell convection disruption might trigger surface geophysical disasters, such as super-volcano eruptions [2-4]. Scientists have a fundamental responsibility to tell the truth and to provide scientific understanding that benefits humanity.

Comprehensive evaluation of the allelopathic potential of Elymus nutans

Drooping wildryegrass (Elymus nutans) has been widely planted together with other perennial grasses for rebuilding degraded alpine meadow atop the Tibetan Plateau. However, the rebuilt sown pastures begin to decline a few years after establishing. One of the possible causes for degradation of sown grassland may come from allelopathy of planted grasses. The purpose of this study was to examine allelopathic potential of drooping wildryegrass. Three types aqueous extracts from drooping wildryegrass and its root zone soil were prepared and 5 highland crops and 5 perennial grasses were used as recipient plants. Drooping wildryegrass exhibited strong allelopathic potential on germination and seedling growth of 5 crops germination and growth, but different crops or perennial grasses respond to the extracts differently. The pieces extract has stronger inhibition than others. Hulless barley, oat and Chinese fescue were the most affected, while quinoa and Siberian wildryegrass were the least affected. Drooping wildryegrass presented less influence on Kentucky bluegrass and crymophylla bluegrass than on Chinese fescue. It is recommended that the species combination of mixture for restoration should consider allopathic effects of the co-seeding and decrease the seeding rate ratio of drooping wildryegrass. The annual dicot crop quinoa and rape seeds can be used as alternative subsequent crop for seed field of drooping wildryegrass monoculture.

Magnetic field generation from primordial black hole distributions

We introduce a statistical method for estimating magnetic field fluctuations generated from primordial black hole (PBH) populations. To that end, we consider monochromatic and extended Press-Schechter PBH mass functions, such that each constituent is capable of producing its own magnetic field due to some given physical mechanism. Assuming linear correlation between magnetic field fluctuations and matter over-densities, our estimates depend on the mass function, the physical field generation mechanism by each PBH constituent, and the characteristic PBH separation. After computing the power spectrum of magnetic field fluctuations, we apply our formalism to study the plausibility that two particular field generation mechanisms could have given rise to the expected seed fields according to current observational constraints. The first mechanism is the Biermann battery and the second one is due to the accretion of magnetic monopoles at PBH formation, constituting magnetic PBHs. Our results show that, for monochromatic distributions, it does not seem to be possible to generate sufficiently intense seed fields in any of the two field generation mechanisms. For extended distributions, it is also not possible to generate the required seed field by only assuming a Biermann battery mechanism. In fact, we report an average seed field by this mechanism of about 10−47 G, at z = 20. For the case of magnetic monopoles we instead assume that the seed values from the literature are achieved and calculate the necessary number density of monopoles. In this case we obtain values that are below the upper limits from current constraints.

Magnetogenesis around the first galaxies: the impact of different field seeding processes on galaxy formation

We study the evolution of magnetic fields generated by charge segregation ahead of ionization fronts during the Epoch of Reionization, and their effects on galaxy formation. We compare this magnetic seeding process with the Biermann battery, injection from supernovae, and an imposed seed field at redshift z ≳ 127. Using a suite of self-consistent cosmological and zoom-in simulations based on the Auriga galaxy-formation model, we determine that all mechanisms produce galactic magnetic fields that equally affect galaxy formation, and are nearly indistinguishable at z ≲ 1.5. The former is compatible with observed values, while the latter is correlated with the gas metallicity below a seed-dependent redshift. Low-density gas and haloes below a seed-dependent mass threshold retain memory of the initial magnetic field. We produce synthetic Faraday rotation measure maps, showing that they have the potential to constrain the seeding process, although current observations are not yet sensitive enough. Our results imply that the ad-hoc assumption of a primordial seed field – widely used in galaxy formation simulations but of uncertain physical origin – can be replaced by physically-motivated mechanisms for magnetogenesis with negligible impact on galactic properties. Additionally, magnetic fields generated ahead of ionization fronts appear very similar but weaker than those produced by the Biermann battery. Hence, in a realistic scenario where both mechanisms are active, the former will be negligible compared to the latter. Finally, our results highlight that the high-redshift Universe is a fruitful testing ground for our understanding of magnetic fields generation.

Seed magnetic fields in turbulent small-scale dynamos

ABSTRACT Magnetic fields in galaxies and galaxy clusters are amplified from a very weak seed value to the observed $\mu$G strengths by the turbulent dynamo. The seed magnetic field can be of primordial or astrophysical origin. The strength and structure of the seed field, on the galaxy or galaxy cluster scale, can be very different, depending on the seed-field generation mechanism. The seed field first encounters the small-scale dynamo, thus we investigate the effects of the strength and structure of the seed field on the small-scale dynamo action. Using numerical simulations of driven turbulence and considering three different seed-field configurations: (1) uniform field, (2) random field with a power-law spectrum, and (3) random field with a parabolic spectrum, we show that the strength and statistical properties of the dynamo-generated magnetic fields are independent of the details of the seed field. We demonstrate that, even when the small-scale dynamo is not active, small-scale magnetic fields can be generated and amplified linearly due to the tangling of the large-scale field. In the presence of the small-scale dynamo action, we find that any memory of the seed field for the non-linear small-scale dynamo generated magnetic fields is lost and thus, it is not possible to trace back seed-field information from the evolved magnetic fields in a turbulent medium.

A 3D simulation of a neutrino-driven supernova explosion aided by convection and magnetic fields

ABSTRACT We study the impact of a small-scale dynamo in core-collapse supernovae using a 3D neutrino magnetohydrodynamics (MHD) simulation of a 15 M⊙ progenitor. The weak seed field is amplified exponentially in the gain region once neutrino-driven convection develops, and remains dominated by small-scale structures. About $250\, \mathrm{ms}$ after bounce, the field energy in the gain region reaches ${\sim } 50{{\ \rm per\ cent}}$ of kinetic equipartition. This supports the development of a neutrino-driven explosion with modest global anisotropy, which does not occur in a corresponding model without magnetic fields. Our results suggest that magnetic fields may play a beneficial subsidiary role in neutrino-driven supernovae even without rapid progenitor rotation. Further investigation into the nature of MHD turbulence in the supernova core is required.

Multi-scale dynamics of magnetic flux tubes and inverse magnetic energy transfer

We report on an analytical and numerical study of the dynamics of a three-dimensional array of identical magnetic flux tubes in the reduced-magnetohydrodynamic description of the plasma. We propose that the long-time evolution of this system is dictated by flux-tube mergers, and that such mergers are dynamically constrained by the conservation of the pertinent (ideal) invariants, viz. the magnetic potential and axial fluxes of each tube. We also propose that in the direction perpendicular to the merging plane, flux tubes evolve in a critically balanced fashion. These notions allow us to construct an analytical model for how quantities such as the magnetic energy and the energy-containing scale evolve as functions of time. Of particular importance is the conclusion that, like its two-dimensional counterpart, this system exhibits an inverse transfer of magnetic energy that terminates only at the system scale. We perform direct numerical simulations that confirm these predictions and reveal other interesting aspects of the evolution of the system. We find, for example, that the early time evolution is characterized by a sharp decay of the initial magnetic energy, which we attribute to the ubiquitous formation of current sheets. We also show that a quantitatively similar inverse transfer of magnetic energy is observed when the initial condition is a random, small-scale magnetic seed field.

Quantitative proteomic analyses of two soybean low phytic acid mutants to identify the genes associated with seed field emergence

Background Seed germination is essential to crop growth and development, and ultimately affects its harvest. It is difficult to breed soybeans low in phytic acid with a higher seed field emergence. Although additional management and selection could overcome the phytate reduction, the mechanisms of seed germination remain unknown. Results A comparative proteomic analysis was conducted between two low phytic acid (LPA) soybean mutants (TW-1-M and TW-1), both of which had a deletion of 2 bp in the GmMIPS1 gene. However, the TW-1 seeds showed a significantly lower field emergence compared to the TW-1-M. There were 282 differentially accumulated proteins (DAPs) identified between two mutants at the three stages. Among these DAPs, 80 were down-accumulated and 202 were up-accumulated. Bioinformatic analysis showed that the identified proteins were related to functional categories of oxidation reduction, response to stimulus and stress, dormancy and germination processes and catalytic activity. KEGG analysis showed that these DAPs were mainly involved in energy metabolism and anti-stress pathways. Based upon the conjoint analysis of DAPs with the differentially expressed genes (DEGs) previously published among three germination stages in two LPA mutants, 30 shared DAPs/DEGs were identified with different patterns, including plant seed protein, beta-amylase, protein disulfide-isomerase, disease resistance protein, pyrophosphate-fructose 6-phosphate 1-phosphotransferase, cysteine proteinase inhibitor, non-specific lipid-transfer protein, phosphoenolpyruvate carboxylase and acyl-coenzyme A oxidase. Conclusions Seed germination is a very complex process in LPA soybean mutants. The TW-1-M and TW-1 showed many DAPs involved in seed germination. The differential accumulation of these proteins could result in the difference of seed field emergence between the two mutants. The high germination rate in the TW-1-M might be strongly attributed to reactive oxygen species-related and plant hormone-related genes. All these findings would help us further explore the germination mechanisms in LPA crops.