Search

Geophysical events implying a large mass displacement especially in the vertical direction can produce a localized change of the Earth gravity field. The Sumatra earthquake of 2004 December is an example of this kind of geophysical phenomena. The aim of this work is to investigate the possibility of detecting such gravimetric changes by exploiting the information coming from gravity space missions. Proper testing procedures to be directly applied into the observation space have been set up. They require to propagate the effect of the geophysical event to the satellite observables and then to compare their track-wise spectra with the instrument noise level. These testing procedures have been applied to a realistic simulation of the gravimetric signal generated by the Sumatra earthquake, considering three different geodetic missions: the forthcoming GOCE mission, recovering a full gravity-gradient tensor, the presently flying GRACE mission, collecting low-low satellite-to-satellite tracking (SST) observations and a possible future gravimetric mission based on the same principle of GRACE, but with an improved accuracy thanks to the use of laser doppler interferometry. The results of the simulations confirm the higher capability of the SST missions of detecting gravity variations due to geophysical phenomena like the Sumatra earthquake. However, this signal could be seen also by a gradiometric mission like GOCE on condition that a considerable amount of observations is collected over the study area after the event. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present the concept of a dedicated gravity field mission for the planet Mars, the Mars Quantum Gravity Mission (MaQuIs). The mission is targeted at improving the data on the gravitational field of Mars, enabling studies on planetary dynamics, seasonal changes, and subsurface water reservoirs. MaQuIs follows well known mission scenarios, currently deployed for Earth, and includes state-of-the-art quantum technologies to enhance the gained scientific signal. • The investigation of Marsian dynamics and composition using quantum technologies. • The application of quantum technologies for general space research outside of Mars. • Impact of gravitational field knowledge on Martian dynamics and composition including open questions. [ABSTRACT FROM AUTHOR]

In this study, the genes of theAux/IAA family were used as functional markers to characterise bud break stages in a white poplar clone. In the first experiment, under greenhouse conditions, the sprouting of repressed sylleptic buds was obtained by pruning the shoot tip during growing season. Buds were collected at 0, 6, 24 and 48 h after pruning for molecular analyses. A decrease in transcript level ofIAA4 andIAA8 genes was observed in the first and second bud below the cut after 6 and 24 h, respectively. In the second experiment, bud break of post-dormant proleptic buds was induced by forcing in climatic chamber. The first 6 and the following 6 buds below the apical one were sampled every 48 h during forcing. Anatomical studies were also carried out on buds and plants were equipped with stem and bud radial growth sensors to check their swelling. In both experiments, gene expression patterns showed a decrease and a successive increase in expression ofIAA4 andIAA8 genes during bud break. The transient down-regulation of these genes was observed only in buds that formed new branches. Thus, similar molecular mechanisms are involved in bud break of both sylleptic and proleptic buds. [ABSTRACT FROM AUTHOR]

A new mutant of Arabidopsis named rha1 is characterized and the gene involved cloned. In roots, the mutant shows minimal right-handed slanting, reduced gravitropic response, notable resistance to 2,4-D, but scarce resistance to IAA and NAA. The roots also show a clear resistance to the auxin transport inhibitors TIBA and NPA, and to ethylene. Other characteristics are a reduced number of lateral roots and reduced size of shoot and root in the seedlings. The gene, cloned through TAIL-PCR, was found to be a heat-shock factor that maps on chromosome 5, close to and above the RFLP marker m61. The rha1 structure, mRNA, and translation product are reported. Since, so far, no other gravitropic mutant has been described as mutated in a heat-shock factor, rha1 belongs to a new group of mutants disturbed in slanting, gravitropism, and auxin physiology. As shown through the RT-PCR analyses of its expression, the gene retains the function connected with heat shock. If the characteristics connected with auxin physiology are considered, however, it is also likely that the gene, as a transcription factor, could be involved in root circumnutation, gravitropic response, and hormonal control of differentiation. Since GUS staining under the gene promoter was localized mainly in the mature tissues, rha1 does not seem to be involved in the first steps of gravitropism, but is rather related to the general response to auxin. The alterations in slanting (mainly due to reduced chiral circumnutation) and gravitropism lead to the supposition that the two processes may have, at least in part, common origins. [ABSTRACT FROM PUBLISHER]

Arabidopsis thaliana roots grown on a vertically set plate do not elongate straight down the gravitational vector, but by making waves and coils, and by conspicuously slanting towards the right‐hand. This behaviour, in a previous paper, was ascribed to the simultaneous effect of three processes: circumnutation, positive gravitropism and negative thigmotropism. However, when the plants are grown on the Random Positioning Machine (RPM), in conditions that are believed to simulate space microgravitational conditions closely, the roots do not show the usual pattern. In the wild type, the roots make large loops to the right‐hand side, whereas in the gravitropic and auxinic mutants aux1, eir1, rha1, they just move randomly around the initial direction. Therefore, if the movements made on the RPM are those produced by the exclusion of gravitropism and negative thigmotropism, as is apparent, the conclusion is that Arabidopsis roots are animated by a form of chiral circumnutation, that is lacking in the auxinic and gravitropic mutants aux1, eir1 and rha1. In addition, the 1 g condition appears to reduce the scatter among the circumnutating tracks produced by the roots of the wild types, but not among those of the mutants. Because there is a scarcity of literature regarding circumnutation in roots, it is not known how widely root chiral circumnutation is spread, but it is known that, in some previously studied species, just random nutations are observed. Two kinds of nutating movements seem to exist in plant roots and, whereas the random process does not seem to be connected with auxin physiology and transport, the chiral process appears to be connected in the same way as gravitropism is. [ABSTRACT FROM PUBLISHER]

The effect of microgravity on the expression of genes for tubulin, stress and aging in Arabidopsis seedlings from wild-type, and the auxinic mutants auxl and eir/pin2 is reported. Simulated microgravity was produced through the Random Positioning Machine (RPM). The results showed that the tubulin genes TUA4, TUA6 and TUB2, in plants subjected to µg, showed a peak of expression at 3h in the wild-type, whereas in the mutants it was delayed to 6h. The microgravity treatment tested on the expression of stress genes FeSODI and CAT3 showed only a significant increase of expression for FeSODI. The gene involved in senescence SAG 12 showed increased expression in the wild-type starting at 3h, whereas in the mutant a significant increase was seen only at 24h. From the collected data we conclude that auxin transport and action should be involved in tubulin synthesis, stress, and the senescence process. [ABSTRACT FROM AUTHOR]