Effects of variations in soil water potential,depth of N placement,and cultivar on postanthesis N uptake by wheat

This study was conducted to investigate the influence of soil water potential, depth of N placement, timing, and cultivar on uptake of a small dose of labeled N applied after anthesis by wheat (Triticum aestivum L.) Understanding postanthesis N accumulation should allow better control of grain protein concentration through proper manipulation of inputs. Two hard, red spring-wheat cultivars were planted in early and late fall each yr of a 2-yr field experiment. Less than 1 kg N ha^–1 as K ¹⁵NO₃ was injected into the soil at two depths: shallow (0.05 to 0.08 m) and deep (0.15 to 0.18 m). In both years an irrigation was applied at anthesis, and injections of labeled N were timed 4, 12, and 20 days after anthesis (DAA). Soil water potential was estimated at the time of injection. Mean recovery of ¹⁵N in grain and straw was 57% of the ¹⁵N applied. Recovery did not differ between the high-protein (Yecora Rojo) and the low-protein (Anza or Yolo) cultivars. Mean recovery from deep placement was 60% versus only 54% from shallow placement (p < 0.01). Delaying the time of injection decreased mean recovery significantly from 58% at 4 DAA to 54% at 20 DAA. This decrease was most pronounced in the shallow placement, where soil drying was most severe. Regressions of recovery on soil water potential of individual cultivar x yr x planting x depth treatments were significant only under the driest conditions. Stepwise regression of ¹⁵N recovery on soil water potential and yield parameters using data from all treatments of both years resulted in an equation including soil water potential and N yield, with a multiple correlation coefficient of 0.64. The translocation of ¹⁵N to grain was higher (0.89) than the nitrogen harvest index (0.69), and showed a highly significant increase with increase in DAA. This experiment indicates that the N uptake capacity of wheat remains reasonably constant between 4 and 20 DAA unless soil drying is severe.     

Fire effects on ecosystem nitrogen cycling in a Californian bishop pine forest

Fire can cause severe nitrogen (N) losses from grassland, chaparral, and temperate and boreal forest ecosystems. Paradoxically, soil ammonium levels are markedly increased by fire, resulting in high rates of primary production in re-establishing plant communities. In a manipulative experiment, we examined the influence of wild-fire ash residues on soil, microbial and plant N pools in a recently burned Californian bishop pine (Pinus muricata D. Don) forest. Ash stimulated post-fire primary production and ecosystem N retention through direct N inputs from ash to soils, as well as indirect ash effects on soil N availability to plants. These results suggest that redistribution of surface ash after fire by wind or water may cause substantial heterogeneity in soil N availability to plants, and could be an important mechanism contributing to vegetation patchiness in fire-prone ecosystems. In addition, we investigated the impact of fire on ecosystem N cycling by comparing ¹⁵N natural abundance values from recently burned and nearby unburned P. muricata forest communities. At the burned site, ¹⁵N natural abundance in recolonising species was similar to that in bulk soil organic matter. By contrast, there was a marked ¹⁵N depletion in the same species relative to the total soil N pool at the unburned site. These results suggest that plant uptake of nitrate (which tends to be strongly depleted in ¹⁵N because of fractionation during nitrification) is low in recently burned forest communities but could be an important component of eco- system N cycling in mature conifer stands. Received: 29 June 1999 / Accepted: 24 October 1999     

Local anaesthetic lidocaine modulates epiphyllous bud differentiation in Kalanchoe pinnata

A single treatment with lidocaine(2-Diethylamino-N-[2,6-dimethylphenyl]-acetamide) – a potent localanaesthetic(LA), caused significant and extensive inhibition of epiphyllous buddifferentiation in Kalanchoe pinnata, in a long –term irreversible manner. These effects were both concentration and treatmentduration dependent, with either variant generating similar and additiveeffects.The growth responses studied had differential sensitivity towards the applieddosage of the anaesthetic. Lidocaine also appears to influence expression oftheorganogenic potential of buds since for all inhibitory doses a significantpercentage produced shoots but not roots.     

Noncanonical Transforming Growth Factor β (TGFβ) Signaling in Cranial Neural Crest Cells Causes Tongue Muscle Developmental Defects

Microglossia is a congenital birth defect in humans and adversely impacts quality of life. In vertebrates, tongue muscle derives from the cranial mesoderm, whereas tendons and connective tissues in the craniofacial region originate from cranial neural crest (CNC) cells. Loss of transforming growth factor β (TGFβ) type II receptor in CNC cells in mice (Tgfbr2^fl/fl;Wnt1-Cre) causes microglossia due to a failure of cell-cell communication between cranial mesoderm and CNC cells during tongue development. However, it is still unclear how TGFβ signaling in CNC cells regulates the fate of mesoderm-derived myoblasts during tongue development. Here we show that activation of the cytoplasmic and nuclear tyrosine kinase 1 (ABL1) cascade in Tgfbr2^fl/fl;Wnt1-Cre mice results in a failure of CNC-derived cell differentiation followed by a disruption of TGFβ-mediated induction of growth factors and reduction of myogenic cell proliferation and differentiation activities. Among the affected growth factors, the addition of fibroblast growth factor 4 (FGF4) and neutralizing antibody for follistatin (FST; an antagonist of bone morphogenetic protein (BMP)) could most efficiently restore cell proliferation, differentiation, and organization of muscle cells in the tongue of Tgfbr2^fl/fl;Wnt1-Cre mice. Thus, our data indicate that CNC-derived fibroblasts regulate the fate of mesoderm-derived myoblasts through TGFβ-mediated regulation of FGF and BMP signaling during tongue development.     

Brain-derived neurotrophic factor (BDNF) mediates bone morphogenetic protein-2 (BMP-2) effects on cultured striatal neurones

Bone morphogenetic proteins are members of the transforming growth factor-beta superfamily that have multiple functions in the developing nervous system. One of them, bone morphogenetic protein-2 (BMP-2), promotes the differentiation of cultured striatal neurones, enhancing dendrite growth and calbindin-positive phenotype. Bone morphogenetic proteins have been implicated in cooperative interactions with other neurotrophic factors. Here we examined whether the effects of BMP-2 on cultured striatal neurones are mediated or enhanced by other neurotrophic factors. BMP-2 had a cooperative effect with low doses of brain-derived neurotrophic factor or neurotrophin-3 (but not with other neurotrophic factors such as glial cell line-derived neurotrophic factor, neurturin or transforming growth factor-beta 2) on the number of calbindin-positive striatal neurones. Moreover, BMP-2 induced phosphorylated Trk immunoreactivity in cultured striatal neurones, suggesting that neurotrophins are involved in BMP-2 neurotrophic effects. The addition of TrkB-IgG or antibodies against brain-derived neurotrophic factor abolished the effects of BMP-2 on the number and degree of differentiation of calbindin-positive striatal neurones. Indeed, BMP-2 treatment increased brain-derived neurotrophic factor protein levels in treated cultures media and BDNF immunocytochemistry revealed that this neurotrophin was produced by neuronal cells. Taken together, these results indicate that brain-derived neurotrophic factor mediates the effects of BMP-2 on striatal neurones.     

In vitro culture of human chondrocytes (1): A novel enhancement action of ferrous sulfate on the differentiation of human chondrocytes

Chondrogenic differentiation of mesenchymal cells is generally thought to be initiated by the inductive action of specific growth factors and depends on intimate cell-cell interactions. The aim of our investigation was to characterize the influences of basic fibroblast growth factor (bFGF) and ferroussulfate (FeSO₄) on proliferation and differentiation of human articular chondrocytes (HAC). This is the first report of the effects of FeSO₄ on chondrogenesis of HAC. Multiplied chondrocytes of hip and shoulder joints were cultured in chondrocyte growth medium supplemented with bFGF, FeSO₄, or both bFGF + FeSO₄ for4weeks. A 20 μl aliquot of a cell suspension containing2 × 10⁷ cells ml⁻¹ was delivered onto each well of 24-well tissue culture plates. Cells cultured with the growth medium only was used as a control. Alamar blue and alcian blue staining were done to determine the chondrocyte proliferation and differentiation, respectively, after 4 weeks. The samples exposed to bFGF, FeSO₄, and combination of both indicated sufficient cell proliferation similar to the control level. Differentiations of the HAC exposed to bFGF, FeSO₄,and bFGF + FeSO₄ were 1.2-, 2.0-, and 2.2-fold of the control, respectively. Therefore, chondrocyte differentiation was significantly enhanced by the addition of FeSO₄ andbFGF + FeSO₄. The combined effects of bFGF and FeSO₄ were additive, rather than synergistic. These results suggest that treatment with ferrous sulfate alone or in combination with basic fibroblast growth factor etc, is a powerful tool to promote the differentiation of HAC for the clinical application. This revised version was published online in August 2006 with corrections to the Cover Date.     

<Emphasis Type="Italic">In vitro</Emphasis> selection and regeneration of chrysanthemum (<Emphasis Type="Italic">Dendranthema grandiflorum</Emphasis> Tzelev) plants resistant to culture filtrate of <Emphasis Type="Italic">Septoria obesa</Emphasis> Syd

Callus cultures derived from leaf segments of chrysanthemum cultivar ‘Snow Ball’ which was susceptible to Septoria obesa were successfully used for in vitro selection for resistance to this pathogenic fungus. Resistant cell lines were selected by culturing callus on growth medium containing various concentrations of S. obesa filtrate. Resistant calluses obtained after two cycles (30 d each cycle) of selection were used for plant regeneration. About 30% of the plants regenerated from the resistant calluses and 70–80% of the plants raised from cuttings had acquired considerable resistance against the pathogen in the field. No phenotypic variation was observed in the selected regenerates.