Seed birth to death Kumar, S. P. Jeevan; Prasad, S. Rajendra; Banerjee, Rintu ...
Annals of botany,
09/2015, Letnik:
116, Številka:
4
Journal Article
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Odprti dostop
Reactive oxygen species (ROS) are considered to be detrimental to seed viability. However, recent studies have demonstrated that ROS have key roles in seed germination particularly in the release of ...seed dormancy and embryogenesis, as well as in protection from pathogens.
This review considers the functions of ROS in seed physiology. ROS are present in all cells and at all phases of the seed life cycle. ROS accumulation is important in breaking seed dormancy, and stimulating seed germination and protection from pathogens. However, excessive ROS accumulation can be detrimental. Therefore, knowledge of the mechanisms by which ROS influence seed physiology will provide insights that may not only allow the development of seed quality markers but also help us understand how dormancy can be broken in several recalcitrant species.
Reactive oxygen species have a dual role in seed physiology. Understanding the relative importance of beneficial and detrimental effects of ROS provides great scope for the improvement and maintenance of seed vigour and quality, factors that may ultimately increase crop yields.
It is commonly assumed that recognition and discrimination of chirality, both in nature and in artificial systems, depend solely on spatial effects. However, recent studies have suggested that charge ...redistribution in chiral molecules manifests an enantiospecific preference in electron spin orientation. We therefore reasoned that the induced spin polarization may affect enantiorecognition through exchange interactions. Here, we show experimentally that the interaction of chiral molecules with a perpendicularly magnetized substrate is enantiospecific. Thus, one enantiomer adsorbs preferentially when the magnetic dipole is pointing up, whereas the other adsorbs faster for the opposite alignment of the magnetization. The interaction is not controlled by the magnetic field per se, but rather by the electron spin orientations, and opens prospects for a distinct approach to enantiomeric separations.
Oilseeds are crucial for the nutritional security of the global population. The conventional technology used for oil extraction from oilseeds is by solvent extraction. In solvent extraction,
n
...-hexane is used as a solvent for its attributes such as simple recovery, non-polar nature, low latent heat of vaporization (330 kJ/kg) and high selectivity to solvents. However, usage of hexane as a solvent has lead to several repercussions such as air pollution, toxicity and harmfulness that prompted to look for alternative options. To circumvent the problem, green solvents could be a promising approach to replace solvent extraction. In this review, green solvents and technology like aqueous assisted enzyme extraction are better solution for oil extraction from oilseeds. Enzyme mediated extraction is eco-friendly, can obtain higher yields, cost-effective and aids in obtaining co-products without any damage. Enzyme technology has great potential for oil extraction in oilseed industry. Similarly, green solvents such as terpenes and ionic liquids have tremendous solvent properties that enable to extract the oil in eco-friendly manner. These green solvents and technologies are considered green owing to the attributes of energy reduction, eco-friendliness, non-toxicity and non-harmfulness. Hence, the review is mainly focussed on the prospects and challenges of green solvents and technology as the best option to replace the conventional methods without compromising the quality of the extracted products.
Abstract
Luminous Red Variables are most likely eruptions that are the outcome of stellar mergers. V838 Mon is one of the best-studied members of this class, representing an archetype for stellar ...mergers resulting from B-type stars. As result of the merger event, “nova-like” eruptions occur driving mass loss from the system. As the gas cools considerable circumstellar dust is formed. V838 Mon erupted in 2002 and is undergoing very dynamic changes in its dust composition, geometry, and infrared luminosity providing a real-time laboratory to validate mineralogical condensation sequences in stellar mergers and evolutionary scenarios. We discuss recent NASA Stratospheric Observatory for Infrared Astronomy 5–38
μ
m observations combined with archival NASA Spitzer spectra that document the temporal evolution of the freshly formed (within the last ≲20 yr) circumstellar material in the environs of V838 Mon. Changes in the 10
μ
m spectral region are strong evidence that we are witnessing a classical dust condensation sequence expected to occur in oxygen-rich environments where alumina formation is followed by that of silicates at the temperature cools.
ABSTRACT
We present an analysis of the evolution of circumstellar dust and molecules in the environment of the very late thermal pulse object V4334 Sgr (Sakurai’s object) over an ∼20-yr period, ...drawing on ground-, airborne-, and space-based infrared photometry and spectroscopy. The dust emission, which started in 1997, resembles a blackbody that cooled from ∼1200 K in 1998 August to ∼180 K in 2016 July. The dust mass, assuming amorphous carbon, was ∼5 × 10−10 M⊙ in 1998 August, and we estimate that the total dust mass was ∼2 × 10−5 M⊙ by ∼2016. The appearance of a near-infrared excess in 2008 suggests that a new episode of (or renewed) mass-loss began then. We infer lower limits on the bolometric luminosity of the embedded star from that of the dust shell, which rose to ∼16 000 L⊙ before declining to ∼3000 L⊙. There is evidence for weak 6–7 μm absorption, which we attribute to hydrogenated amorphous carbon formed in material ejected by Sakurai’s object during a mass ejection phase that preceded the 1997 event. We detect small hydrocarbon and other molecules in the spectra, and trace the column densities in hydrogen cyanide (HCN) and acetylene (C2H2). We use the former to determine the 12C/13C ratio to be 6.4 ± 0.7, 14 times smaller than the Solar system value.
We present 5-28 m SOFIA FORECAST spectroscopy complemented by panchromatic X-ray through infrared observations of the CO nova V5668 Sgr documenting the formation and destruction of dust during ∼500 ...days following outburst. Dust condensation commenced by 82 days after outburst at a temperature of ∼1090 K. The condensation temperature indicates that the condensate was amorphous carbon. There was a gradual decrease of the grain size and dust mass during the recovery phase. Absolute parameter values given here are for an assumed distance of 1.2 kpc. We conclude that the maximum mass of dust produced was 1.2 × 10−7 M if the dust was amorphous carbon. The average grain radius grew to a maximum of ∼2.9 m at a temperature of ∼720 K around day 113 when the shell visual optical depth was τv ∼ 5.4. Maximum grain growth was followed by a period of grain destruction. X-rays were detected with Swift from day 95 to beyond day 500. The Swift X-ray count rate due to the hot white dwarf peaked around day 220, when its spectrum was that of a kT = 35 eV blackbody. The temperature, together with the supersoft X-ray turn-on and turn-off times, suggests a white dwarf mass of ∼1.1 M . We show that the X-ray fluence was sufficient to destroy the dust. Our data show that the post-dust event X-ray brightening is not due to dust destruction, which certainly occurred, as the dust is optically thin to X-rays.
Abstract
CK Vulpeculae (CK Vul), which erupted in AD 1670–71, was long considered to be a nova outburst; however, recent observations have required that alternative scenarios be considered. Long-slit ...infrared spectroscopy of a forbidden line of iron reported here has revealed high line-of-sight velocities (∼±900 km s
−1
) of the ansae at the tips of the bipolar lobes imaged in H
α
in 2010. The deprojected velocities of the tips are approximately ±2130 km s
−1
assuming the previously derived inclination angle of 65° for the axis of cylindrical symmetry of the bipolar nebula. Such high velocities are in stark contrast to previous reports of much lower expansion velocities in CK Vul. Based on the deprojected velocities of the tips and their angular expansion measured over a 10 yr baseline, we derive a revised estimate, with estimated uncertainties, of
kpc for the distance to CK Vul. This implies that the absolute visual magnitude at the peak of the 1670 explosion was
, indicating that the 1670 event was far more luminous than previous estimates and brighter than any classical nova or any Galactic stellar merger. We propose that CK Vul belongs to the class of intermediate-luminosity optical transients (ILOTs), objects which bridge the luminosity gap between novae and supernovae. While eruptions in lower luminosity ILOTs are attributed to merger events, the origin of the highly luminous ILOT outbursts is currently not known.
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•UAE had higher lipid content 43 ± 0.33% (w/w) than Soxhlet (30 ± 0.28) and BS (36 ± 0.38).•Lipid content of 43 ± 0.33% (w/w) obtained in 20 min at 30 °C, 50 Hz frequency and ...2800 W.•UAE maintained quality of lipids on par with conventional lipid extraction.•UAE is a greener technique, which reduced time, energy and solvent consumption.
Soaring demand for alternative fuels has been gaining wide interest due to depletion of conventional fuel, increasing petroleum prices and greenhouse gas emissions. Biodiesel, an alternative fuel, derived from oleaginous microbes has been promising because of short incubation time and easy to scale up. Oleaginous yeast Trichosporon sp. is capable of utilizing glycerol and agro-residues for enhanced lipid synthesis. Lipid extraction from Trichosporon sp. biomass showed highest lipid content with ultrasonic assisted extraction (43 ± 0.33%, w/w) coupled with process parameters than the conventional Soxhlet (30 ± 0.28%, w/w) and Binary solvent choloroform:methanol, (2:1, v/v) methods (36 ± 0.38%, w/w), respectively. The standardized process parameters of ultrasonic assisted extraction coupled with chloroform/methanol solvent system resulted 95–97% of conversion efficiency in 20 min at 30 °C with a frequency of 50 Hz and 2800 W power, respectively. Enzymatic transesterification of yeast biomass lipid obtained 85% of fatty acid methyl esters that are predominant with oleic acid methyl ester followed by palmitic and stearic acid methyl esters, respectively. These results substantiate that the ultrasonic assisted extraction is a potential green extraction technique that had reduced time, energy and solvent consumption without compromising on lipid quality. Deploying this green extraction technique could make the biodiesel production process inexpensive and eco-friendly.
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