Reciprocal adjustments between landforms and living organisms: Extended geomorphic evolutionary insights

Whilst biological organisms adapt to the environment, earth surface processes and landforms evolve as a result of physicochemical processes, and as the result of the activity of certain living organisms defined as ‘ecosystem engineers’. The importance of long- and short-term impacts on geomorphic structures and processes by ecosystem engineers appears to be underestimated. Recent recognition of complex abiotic–biotic feedbacks in nature has resulted in a convergence of approaches in ecology and geomorphology. Present biogeomorphic knowledge supports the hypothesis that abiotic–biotic feedbacks create characteristic modulated patterns of earth surface landforms, adjusting according to biological evolution in the long term and to ecological succession in the short term. In this context, natural selection of organisms and ecological successions are considered to have the potential, in some cases, for extension to the physical world, including earth surface landforms. This perspective aims to contribute to the disruption of the ‘classical’ dichotomy between abiotic–biotic compartments because it emphasizes reciprocal adjustments (i.e., feedback mechanisms) between living organisms and abiotic environment dynamics. The extended evolutionary perspective, that is intended to feed back to ecology and evolutionary biology, indicates the potential for change in our deep understanding of geomorphology to reflect evolutionary and ecological succession theories.     

Automorphic soils of the central and southern Timan Ridge

Automorphic loamy soils developing from different parent materials in the central and southern parts of the Timan Ridge are described. Pale-podzolic soil and iron-illuvial texture-differentiated svetlozems are developed from silty covering loams underlain by moraine deposits. Podzolic, iron-illuvial, cryometamorphic, and clay-illuvial horizons are distinguished in the svetlozems; soils with such a complex morphology have been described in the taiga zone of European Russia for the first time. Humus-iron-illuvial podzols are developed from acidic slates. Raw-humus rzhavozems (iron-metamorphic soils) are developed from substrates with the high content of pebbles of mafic rocks. Such soils are typical of the middle taiga zone of Central Siberia and the south of Far East. In the northwestern part of European Russia, these soils occupy small areas.     

The fate and toxicity of the flavonoids naringenin and formononetin in soil

The flavonoid class of plant secondary metabolites play a multifunctional role in below-ground plant–microbe interactions with their best known function as signals in the nitrogen fixing legume–rhizobia symbiosis. Flavonoids enter rhizosphere soil as a result of root exudation and senescence but little is known about their subsequent fate or impacts on microbial activity. Therefore, the present study examined the sorptive behaviour, biodegradation and impact on dehydrogenase activity (as determined by iodonitrotetrazolium chloride reduction) of the flavonoids naringenin and formononetin in soil. Organic carbon normalised partition coefficients, log K_oc, of 3.12 (formononetin) and 3.19 (naringenin) were estimated from sorption isotherms and, after comparison with literature log K_oc values for compounds whose soil behaviour is better characterised, the test flavonoids were deemed to be moderately sorbed. Naringenin (spiked at 50 μg g^?1) was biodegraded without a detectable lag phase with concentrations reduced to 0.13±0.01 μg g^?1 at the end of the 96 h time course. Biodegradation of formononetin proceeded after a lag phase of ～24 h with concentrations reduced to 4.5±1% of the sterile control after 72 h. Most probable number (MPN) analysis revealed that prior to the addition of flavonoids, the soil contained 5.4×10⁶ MPN g^?1 (naringenin) and 7.9×10⁵ MPN g^?1 (formononetin) catabolic microbes. Formononetin concentration had no significant (p>0.05) effect on soil dehydrogenase activity, whereas naringenin concentration had an overall but non-systematic impact (p=0.045). These results are discussed with reference to likely total and bioavailable concentrations of flavonoids experienced by microbes in the rhizosphere.     

The influence of carbonates in parent rocks on the biological properties of mountain soils of the Northwest Caucasus region

The biological activity of different subtypes of soddy-calcareous soils (rendzinas) of the Northwest Caucasus region was studied. In the Novorossiisk-Abrau-Dyurso region (dry subtropics), typical soddy-calcareous soils with the high content of carbonates predominate; in the more humid conditions of the Lagonaki Plateau (Republic of Adygeya), leached soddy-calcareous soils carbonate-free down to the parent rock are spread. The number of microarthropods, the populations of fungi and bacteria, and the enzyme activity (catalase, dehydrogenase, and invertase) testify that the biological activity of these soils significantly differs. In the typical soddy-calcareous soils of the dry subtropics, the content of carbonates does not affect the characteristics mentioned; in the more humid conditions of the West Caucasus region, the presence of carbonates in the parent rocks intensifies the biological activity of the soddy-calcareous soils.     

Evaluation of Near Infra-red Reflectance Spectroscopy for Predicting Grain and Stover Quality Traits in Maize

The prediction of grain and stover quality parameters in maize {Zea mays L.) by near infra-red reflectance spectroscopy (NIRS) was studied. A total of 110 grain and 135 stover samples originating from different genotypes and environments were assayed. Calibration equations for content of crude protein (CP), crude fat (CF), starch (ST), and water soluble carbohydrates (WSC) in grain were obtained by multiple linear regression of known manual values on NIRS data from the odd numbered samples. Calibrations for CP, acid detergent fibre (ADF), in vitro digestible organic matter according to the Tilley & Terry (IVDOM-T & T) and the gas production (IVDOM-Gp) method, respectively, and metabolizable energy (ME) in stover were developed analogously. Equations were validated with the evennumbered .samples and for ME additionally with the 1584 stover samples from an experiment with 66 F₁ hybrids tested in six environments. The coefficients of multiple determination (R²) of the prediction equations ranged from 0.80 for IVDOM-Gp and ME in stover to 0.94 for CP in grain. Standard errors of calibration (SEC) and prediction (SEP) were in most cases not higher than commonly reported for conventional manual assays. With regard to the correct ranking of hybrids, prediction equations for ME applied well to stover samples from other environments with one exception. We concluded that NIRS can evaluate the quality traits investigated to a similar degree to that of conventional methods of analysis. Since NIRS is simple and safe to operate and allows rapid screening of several quality traits simultaneously, it should be particularly attractive for breeding purposes.     

Conformations at local energy minimums for gramicidin S: optical calculations

Energy minimization techniques applied to an arbitrary peptide primary sequence result in a still large number of hypothetical structures of similar energy. Optical activity calculations can, in principle, be used to screen the low-energy conformations. Those conformations which yield a spectrum different from the observed spectrum by a factor greater than the current reliability of the calculation can be excluded. The method is applied to gramicidin S.     

Extraction and characterization of water–repellent materials from Australian soils

Organic materials responsible for water–repellency in some Australian soils were extracted with an amphiphilic mixture of iso -propanol/15.7 m ammonia (7:3, v:v) in a Soxhlet apparatus, after which the water–repellent soils were rendered wettable. The successful extraction by an organic solvent system indicates that the bulk of hydrophobicity in these soils is not covalently linked to the surface of the sand. The extracted materials restored hydrophobicity on acid washed sands or ignited sands at levels comparable to the original soils.
Spectroscopic and chromatographic examination of the extracted materials indicated that both free and esterified long–chain, 16–32 carbon atom, fatty acids were present with a bimodal distribution showing maxima at C₁₆ and C₂₂. The ¹³C–NMR and infrared spectra of the most hydrophobic extract suggest that hydrophobicity is caused by molecules with extensive polymethylene chains. Calculations with model compounds indicate that at least a close packed monolayer is required before measurable hydrophobicity can be detected with the molarity of ethanol droplet penetration test.     

Impact of UV-C irradiation on the cell wall-degrading enzymes during ripening of tomato (Lycopersicon esculentum L.) fruit

The effect of a hormic dose of UV-C (254 nm) on changes in fruit firmness and cell wall-degrading enzyme (CWDE) activity was determined using tomato fruit. Throughout the storage period, a decrease in firmness was jointly observed with an increase of the CWDE (polygalacturonase, pectin methyl esterase, cellulase, xylanase, beta-D-galactosidase, and protease) activity for all treatments, suggesting the involvement of these enzymes in the ripening process. However, the enhancement in the activity of the CWDE was significantly less in fruit subjected to the hormic dose of UV-C. This reduction may explain why irradiated fruit were firmer than control and consequently may explain how UV-C could delay the ripening and senescence process. We suggest that the CWDE are one of the targets of the UV-C, and by this action, irradiation contributed to a delay of the cell wall degradation and consequently retarded softening of the tomato fruit tissues.