Search

Neste trabalho, objetivou-se quantificar a produção de matéria seca e os conteúdos de B, Ca e Mg na cultura da soja cultivada em solos com diferentes texturas que receberam doses crescentes de B e calagem, e correlacionar o conteúdo de B absorvido pela planta com o teor de B recuperado com água e CaCl2 ferventes sob influência de doses de boro e a calagem aplicadas em três solos distintos. O experimento foi conduzido em casa de vegetação em esquema fatorial 3 x 2 x 6, consistindo de três solos: textura arenosa (RQ), textura média (LVA1) e textura argilosa (LVA2), com e sem calagem, e seis doses de B (0; 1,5; 3; 6; 9 e 15 mg dm-3), em blocos casualizados com três repetições. Determinou-se o teor de B no solo extraível com água e CaCl2 ferventes após 45 dias da adição das doses de B aos solos, massa de matéria seca da parte aérea e os teores de B, Ca e Mg na soja. Os teores de B recuperado, tanto pela água fervente, quanto pelo CaCl2 fervente foram semelhantes nos três solos estudados e, apresentaram altas correlações com o conteúdo de B e o peso de matéria seca. As doses de B adicionadas aumentaram a sua absorção pelas plantas, mas causaram redução na produção de matéria seca da parte aérea nos solos RQ (textura arenosa), LVA1 (textura média) e o LVA2 (textura argilosa) com calagem, neste último solo, o efeito é minimizado na presença de maior teor de argila.This work aimed to quantify the dry matter production and the contents of B, Ca and Mg in soybean plants grown in soils with different textures, which received increasing doses of B, and liming. Additionally, it was correlated the B contents in the plants with the B recovered from the soil with boiling water and CaCl2. The experiment was carried out in a greenhouse in a factorial 3 x 2 x 6 (three soils: sand texture (RQ), loamy sand (LVA1) and clayey (LVA2) textures; with and without liming; and six B doses: 0; 1,5; 3; 6; 9 and 15 mg dm-3) arranged in a entirely randomized block design with three replications. It was determined the soil B extracted with boiling water and CaCl2 45 days after the addition of the B doses to the soil. The shoots dry matter weight and theer B contents in the soybean plants were determined. The mean concentrations of B recovered by both boiling water and boiling CaCl2 were similar for the three soils and were highly correlated with the B contents in the plants and with the dry matter production. The B doses added increased B concentration in the plants, but they decreased dry matter production in the RQ soil, and in the LVA 1 and LVA2 soils with liming. The detrimental effect of high B in the dry matter production was lowered in the soils with higher clay and organic matter concentrations.

Effective population size as a parameter closely correlating with the genetic and genotypic diversity of the seed orchard output is an important indicator of seed orchard functioning. It is determined by the variation of male and female gametic contributions of parental genotypes (including those outside the seed orchard), influenced by the variation in male and female gamete production, reproductive phenology, pollen dispersal within seed orchard and other factors. We assessed male and female fecundity, as well as temporal course of male and female flowering in two seed orchards of Pinus nigra Arnold and Fraxinus excelsior L. / F. angustifolia Vahl. in Slovakia. In both cases, male and female gametic contributions of plus-tree clones were modeled on the basis of fecundity and flowering phenology, and were used to calculate status number as an estimator of effective population size. In the seed orchard of Pinus nigra, marker-aided verification of clonal fidelity revealed unexpectedly high proportion of misplaced ramets (29.9%) and alien genotypes (44.4%). Monitoring of reproductive processes in 2002 and 2003 showed high variation in both male and female fecundity, and pollen shedding preceding female receptivity in Pinus nigra. All these factors contributed to a very low relative status effective number, representing 8.6% to 38.6% of the population census (depending from the management option in relation to misplaced and alien genotypes). In the mixed seed orchard of Fraxinus excelsior and F. angustifolia, the proportion of misplaced and alien genotypes was much lower (22.4% and 12.3%, respectively). However, a high fecundity variation and protogyny resulted in a low relative status number (18.8% to 29.5% of the census number of clones) also in this seed orchard. Practical implications of these findings are shortly discussed and practical management options are proposed. [ABSTRACT FROM AUTHOR]

Response of 16 oilseed rape genotypes to B (boron) toxicity was analyzed by comparing the results of two experiments conducted in a glasshouse. In Experiment 1 plants were grown in standard nutrient solutions with 10 μM B (control) and 1000 μM B. Relative root and shoot growth varied from 20-120% and 31-117%, respectively. Variation in B concentration in shoots was also wide (206.5-441.7 µg B g-1 DW) as well as total B uptake by plant (62.3-281.2 µg B g-1). Four selected genotypes were grown in Experiment 2 in pots filled with high B soil (8 kg ha-1 B; B8). Shoot growth was not affected by B8 treatment, while root and shoot B concentration was significantly increased compared to control. Genotypes Panther and Pronto which performed low relative root and shoot growth and high B accumulation in plants in Experiment 1, had good growth in B8 treatment. In Experiment 2 genotype NS-L-7 had significantly lower B concentration in shots under treatment B8, but also very high B accumulation in Experiment 1. In addition, cluster analyses classified genotypes in three groups according to traits contrasting in their significance for analyzing response to B toxicity. The first group included four varieties based on their shared characteristics that have small value for the relative growth of roots and shoots and large values of B concentration in shoot. In the second largest group were connected ten genotypes that are heterogeneous in traits and do not stand out on any characteristic. Genotypes NS-L-7 and Navajo were separated in the third group because they had big relative growth of root and shoot, but also a high concentration of B in the shoot, and high total B uptake. Results showed that none of tested genotypes could not be recommended for breeding process to tolerance for B toxicity. [ABSTRACT FROM AUTHOR]

Boron (B) toxicity has been found to be a common nutritional disorder in dry areas, where excessive B tends to accumulate in the subsoil. However, in many of the pot experiments on B toxicity, excess B was mixed uniformly in soil or added from the soil surface, a method that does not detect the subsoil B effect. The objective of this plastic-house experiment was to study the effects of different patterns and timings of B application on the development of B toxicity (BT) symptoms, tissue B concentrations, and growth and yield of barley. A three-factor factorial design with three patterns of B application, three timings of B application, and two barley lines was used. A moderately BT-tolerant barley line from the cross 'Arar/Arabic Aswad' (abbreviated as AA) and the moderately BT-susceptible variety 'Harmal' were compared. Each pot consisted of two sections of 20-cm-tall PVC pipe. The second section was watered to field capacity and joined to the bottom of the top section on 25 January (tillering; roots reached the bottom of top section), 15 February (stem elongation), and 20 March (flag leaf emerged for 'Harmal'; booting stage for AA). The three patterns of B application were (1) no B added (-/-), (2) B added to the bottom section only (-/+), and (3) B added to both sections (+/+). The addition of 50 mg B/kg soil increased the hot-water-soluble B level from 0.7 to 21 mg kg-1. Interaction between pattern of B application and timing of B application had significant effects on BT symptom scores and straw B concentrations but not on grain yield. Grain yield of the +/+ treatment was much less than that of -/+, which in turn was less than -/-, but different timings of joining of the pot sections did not have a significant effect on grain yield. Relative to -/-, the percentage of grain yield reduction (8%) sustained by AA when grown in -/+ was less than half of the reduction (18%) suffered by 'Harmal.' In conclusion, subjecting plants to high-B soils from germination to maturity exaggerates the effects of B on rainfed crops in the field. High subsoil B levels can cause significant yield reduction even when roots reach it as late as the boot stage, suggesting the need to screen/breed and grow BT-tolerant cultivars. The use of subsectioned pots introduced in this study is an effective way to simulate BT in the field. [ABSTRACT FROM AUTHOR]

Abstract: Generation of dislocations due to thermal shock in Czochralski (CZ) Si crystal growth under different dipping temperature is investigated. Generation of dislocations due to thermal shock could be suppressed by using a heavily B-doped CZ-Si seed, and the ability for such suppression increased with increasing B concentration in the seed. However, dislocations were generated when the temperature difference before and after the dipping of which a seed was sustained became large. Critical shear stress of B-doped Si crystal with a B concentration of 3×1018 cm−3 at the melting point of Si was estimated to be around 4MPa. [Copyright &y& Elsevier]

Abstract: The energy and electronic properties of heavily B-doped silicon were investigated by density functional theory calculations. Our calculated electronic structures show that the impurity levels mix with valence band edge and the Fermi level locates in the valence band. It supports the metal–superconductor transition mechanism of heavily B-doped silicon, which is similar to that of diamond. A few differences from in diamond that the superconducting critical temperature T C is related to both B concentration and configurations, T C in silicon is only related to B concentration. [Copyright &y& Elsevier]