Field evaluation of somaclonal variation in sunflower (Helianthus annuus L) and its application for crop improvement

Immature zygotic embryos from the American fertility restorer line RHA-857 were used as donor material for induction of direct organogenesis in sunflower (Helianthusannuus L.). The range of spontaneous somaclonal variation among the progenies of regenerants was studied. The genetic modifications observed in regenerants included agronomic traits such as oil content in seed, 1000 seed weight, plant height, leaf width, leaf length, petiole length, internode length, head diameter, number of branches, length of branches, number of ray florets, seed width, seed length, and seed thickness. RAPD molecular analysis carried out on sunflower materials in the R-11 generation showed the absence of a specific 358 bp band in somaclonal line 11/2/51 R. This line showed a modified architecture, full resistance to Phomopsis helianthiand higher oil content in seed in comparison to the standard RHA-857. Line31/3/53 R was with modified architecture and higher 1000 seed weight. Hybrid No. 144 produced with the participation of somaclonal line 20/5/52 R demonstrated high production capacity, shorter vegetation period and reduced height. The combination of these favourable changes is desirable in breeding work on sunflower. Somaclonal variation through director ganogenesis has facilitated the creation of genetically heritable variation in sunflower, which can be used with great success for hybrid seed production of highly productive hybrids. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dynamics of the soil cover in the southeast of Europe and in the southern Trans-Ural region during the subboreal period

An inventory of published data on the natural evolution of forest-steppe, steppe, and semidesert soils in the southern part of the East European Plain and in the southern Trans-Ural region during the Subboreal period of the Holocene has been performed. Schematic maps of the thickness of soil humus profiles and the depth of soil carbonates have been developed for the chronosections of 5000–4200, 4100–3900, and 3800–3200 years ago. On this basis, the areas with specific patterns of natural evolution of soils in the Subboreal period are delineated.     

Particle nucleation in the tropical boundary layer and its coupling to marine sulfur sources

New particle formation in a tropical marine boundary layer setting was characterized during NASA's Pacific Exploratory Mission-Tropics A program. It represents the clearest demonstration to date of aerosol nucleation and growth being linked to the natural marine sulfur cycle. This conclusion was based on real-time observations of dimethylsulfide, sulfur dioxide, sulfuric acid (gas), hydroxide, ozone, temperature, relative humidity, aerosol size and number distribution, and total aerosol surface area. Classic binary nucleation theory predicts no nucleation under the observed marine boundary layer conditions.     

Features of studying of dynamic processes in agrolandscape

Features of existential dynamics of a crop of spring wheat of grade Lada within the limits of agro-landscape moraine hills are investigated. Laws of influence of agroclimatic and landscape conditions on efficiency of culture are revealed. Recommendations on adaptation of manufacture of grain to landscape conditions are given.     

Production and use of biofertilizer based on poultry droppings

It is shown that it is possible to use soil microorganisms for utilizing organic poultry farming wastes with the production of ecologically clean fertilizer that increases the yield and quality of agricultural products. The results obtained are the basis for developing highly effective technologies for environmental rehabilitation.     

Coevolution of soils and vegetation in the southern taiga (with the Prioksko-Terrasnyi reserve as an example)

A detailed characterization of the relief, parent materials, soils, woody vegetation, and the links between them is given for a small part of the southern taiga zone in the center of the East European Plain. A methodology for determining the vegetation succession patterns on different soils with the use of the selectivity coefficient K is suggested. This coefficient is defined as the ratio between the frequency of occurrence of the given tree species on a given soil and its average frequency of occurrence within the entire analyzed area (in the area of the reserve). The values of K change from 0.2 to 3.6 and indicate positive (K > 1) and negative (K < 1) feedback relationships between the soils and vegetation. Changes in the frequencies of occurrence of different tree species on different soils that took place over 19 years have also been studied. It is shown that spruce has a tendency for settling on podzols, mixed spruce-oak-lime forests tend to develop on podzolized podburs, and lime and oak trees tend to develop on soddy podburs. Birch stands are most often replaced by spruce and pine stands; aspen stands and a part of the birch stands are replaced by lime and oak stands. The ecological plasticity of pine trees and the long age of this tree species ensure the existence of a long transitional succession stage with the predominance of pine. These regularities are important for predicting the further development of forest vegetation.     

Excitation energy partitioning and quenching during cold acclimation in Scots pine

We studied the influence of two irradiances on cold acclimation and recovery of photosynthesis in Scots pine (Pinus sylvestris L.) seedlings to assess mechanisms for quenching the excess energy captured by the photosynthetic apparatus. A shift in temperature from 20 to 5 degrees C caused a greater decrease in photosynthetic activity, measured by chlorophyll fluorescence and oxygen evolution, in plants exposed to moderate light (350 micromol m(-2) s(-1)) than in shaded plants (50 micromol m(-2) s(-1)). In response to the temperature shift, maximal photochemical efficiency of photosystem II (PSII), measured as the ratio of variable to maximal chlorophyll fluorescence (Fv/Fm) of dark-adapted samples, decreased to 70% in exposed seedlings, whereas shaded seedlings maintained Fv/Fm close to initial values. After a further temperature decrease to -5 degrees C, only 8% of initial Fv/Fm remained in exposed plants, whereas shaded plants retained 40% of initial Fv/Fm. Seven days after transfer from -5 to 20 degrees C, recovery of photochemical efficiency was more complete in the shaded plants than in the exposed plants (87 and 65% of the initial Fv/Fm value, respectively). In response to cold stress, the estimated functional absorption cross section per remaining PSII reaction center increased at both irradiances, but the increase was more pronounced in exposed seedlings. Estimates of energy partitioning in the needles showed a much higher dissipative component in the exposed seedlings at low temperatures, pointing to stronger development of non-photochemical quenching at moderate irradiances. The de-epoxidation state of the xanthophyll cycle pigments increased in exposed seedlings at 5 degrees C, contributing to the quenching capacity, whereas significant de-epoxidation in the shaded plants was observed only when temperatures decreased to -5 degrees C. Thermoluminescence (TL) measurements of PSII revealed that charge recombinations between the second oxidation state of Mn-cluster S2 and the semireduced secondary electron acceptor quinone Q(B)- (S2Q(B)-) were shifted to lower temperatures in cold-acclimated seedlings compared with control seedlings and this effect depended on irradiance. Concomitant with this, cold-acclimated seedlings demonstrated a significant shift in the S2 recombination with primary acceptor Q(A)- (S2Q(A)-) characteristic TL emission peak to higher temperatures, thus narrowing the redox potential gap between S2Q(B)- and S2Q(A)-, which might result in increased probability for non-radiative radical pair recombination between the PSII reaction center chlorophyll a (P680+) and Q(A)- (P680+)Q(A)-) (reaction center quenching) in cold-acclimated seedlings. In Scots pine seedlings, mechanisms of quenching excess light energy in winter therefore involve light-dependent regulation of reaction center content and both reaction center-based and antenna-based quenching of excess light energy, enabling them to withstand high excitation pressure under northern winter conditions.