The contrasting effects of nutrient enrichment on growth,biomass allocation and decomposition of plant tissue in coastal wetlands

Background

Most studies focus on macronutrient of C, N and P and ignore other elements, which restrict our understanding on the strategy of plant nutrient adaption and nutrient cycling.

Methods

We investigated 14 element (C, N, P, S, K, Ca, Mg, Fe, Mn, Zn, Cu, Na, Al, and Ba) concentrations of green and senesced leaves in Quercus variabilis along the altitude in the Baotianman Mountains, China, and assessed their relationships with climate, soil, and plant functional traits.

Results

Leaf N,S and K increased with, C, Ca, Na, Fe, Mn, Cu and Ba decreased with, and P, Mg, Al, Zn and N:P did not change significantly with altitude. NRE and SRE increased with, and CRE decreased with altitude (p < 0.05). Among the 14 elements, nucleic acid-protein elements (N, K, S and P) were resorbed preferentially, compare to structural (Ca, Mn, and B) and enzymatic (C, Cu, Mg and Zn) that were discriminated against, and toxic (Al and Fe) elements that were totally excluded.

Conclusions

Q. variabilis can synergetically regulate green leaf multielement stoichiometry and nutrient resorption in responses to environment change. Deciduous plants may have a trade-off mechanism at the end of growing season to rebalance somatic nutrients.

     

Heterogeneous effects of tissue inhibitors of matrix metalloproteinases on cardiac fibroblasts

The balance between matrix metalloproteinases (MMPs) and their natural inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), plays a critical role in cardiac remodeling. Although a number of studies have characterized the pathophysiological role of MMPs in the heart, very little is known with respect to the role of TIMPs in the heart. To delineate the role of TIMPs in the heart we examined the effects of adenovirus-mediated overexpression of TIMP-1, -2, -3, and -4 in cardiac fibroblasts. Infection of cardiac fibroblasts with adenoviral constructs containing human recombinant TIMP (AdTIMP-1, -2, -3, and -4) provoked a significant (P < 0.0001) 1.3-fold in increase in bromodeoxyuridine (BrdU) incorporation. Similarly, treatment of cardiac fibroblasts with AdTIMP-1-, -2-, -3-, and -4-conditioned medium led to a 1.2-fold increase in BrdU incorporation (P < 0.0001) that was abolished by pretreatment with anti-TIMP-1, -2, -3, and -4 antibodies. The effects of TIMPs were not mimicked by treating the cells with RS-130830, a broad-based MMP inhibitor, suggesting that the effects of TIMPs were independent of their ability to inhibit MMPs. Infection with AdTIMP-1, -2, -3, and -4 led to a significant increase in alpha-smooth muscle actin staining, consistent with TIMP-induced phenotypic differentiation into myofibroblasts. Finally, infection with AdTIMP-2 resulted in a significant increase in collagen synthesis, whereas infection with AdTIMP-3 resulted in a significant increase in fibroblast apoptosis. TIMPs exert overlapping as well as diverse effects on isolated cardiac fibroblasts. The observation that TIMPs stimulate fibroblast proliferation as well as phenotypic differentiation into myofibroblasts suggests that TIMPs may play an important role in tissue repair in the heart that extends beyond their traditional role as MMP inhibitors.     

Character release following extinction in a Caribbean reef coral species complex

Abstract The Pleistocene extinction of the widespread organ‐pipe Montastraea coral had measurable morphological and ecological effects on surviving lineages of the Montastraea“annularis” species complex. Extinction of the organ‐pipe Montastraea occurred after more than 500,000 years of dominance in the shallow‐water reef habitat of Barbados. Extinction resulted in a morphological shift of the columnar Montastraea lineage from thick to thin columns in modern reef environments. Pleistocene colonies of the columnar morphotype sympatric with organ‐pipe Montastraea showed greater column widths than those in allopatry. We subjected our data to a number of criteria for interpreting the morphological shift as character release following lifting of competitive pressure after extinction. The morphological differences do not appear to be due either to chance or to physical properties of the marine environment. Differential local extinction and recolonization of four members of the species complex did not occur on Barbados, so that the species coexisted and appear to have coevolved between more than 600,000 and 82,000 years ago. The morphological shift is related to coral growth form and growth rate, and thus reflects the acquisition of a primary resource in corals‐light. Character release occurred at the same oceanic Caribbean island (Barbados) where environments have fluctuated with similar variance throughout the period of coexistence. Not only has competition among living members of the Montastraea“annularis” species complex been convincingly demonstrated, but trends in relative abundance among fossil members of the species complex strongly suggest that a competitive hierarchy was operating during their Pleistocene coexistence on Barbados. We also observed an ecological analogue to character release on another Caribbean island, Curaçao. The distribution and abundance of living columnarM. annularis s.s. and massive M. faveolata from the leeward reef crest in Curaçao is greater now than in the Pleistocene, when organ‐pipe Montastraea dominated this shallow‐water reef habitat. Extinction of the faster growing, shallow‐water organ‐pipe Montastraea resulted in higher abundance of the columnar Montastraea lineage in shallow‐water habitats, where it shifted its morphology to one adapted to high light levels. The species extinction released surviving lineages from a competitive network that had resulted in lower rank abundance in the Pleistocene community and enhanced abundance of both columnar M. annularis s.s. and M. faveolata in modern communities. Full validation of our interpretation of character release must await experiments that demonstrate whether phenotypic differences between populations have a genetic basis. However, we believe the results of this study point to the important, yet heretofore neglected, role that biological interactions have played in the evolution of closely related reef coral species.     

Decomposition of mangrove roots depends on the bulk density they grew in

Plant and Soil - Mangroves hold large organic carbon (C) stocks in their soils. These C stocks are mainly attributed to the high productivity and slow decomposition of the below-ground biomass....     

Restriction of placental growth in sheep enhances placental metabolism of fetal beta-endorphin-like immunoreactivity

The opioid polypeptide beta-endorphin is present in fetal blood but it is not clear whether its source is the fetus or the placenta. We therefore measured beta-endorphin in extracts of fetal femoral arterial and umbilical venous blood plasma in sheep by radioimmunoassay to determine whether the fetus or the placenta is the major source of beta-endorphin in the fetal circulation. Chromatographic analysis of extracts of fetal arterial plasma showed that beta-lipotropin and other precursors of beta-endorphin made only a minor contribution to the immunoreactivity detected. Concentrations of immunoreactive beta-endorphin were higher in the femoral artery than in the umbilical vein in fetal sheep between 113 and 128 days of pregnancy. Therefore the placenta removes beta-endorphin or a closely related polypeptide of fetal origin from the umbilical circulation in sheep at this stage of gestation. Acute hypoxaemia and hypoglycaemia increase the concentrations of immunoassayable beta-endorphin in blood plasma of adult and fetal sheep, but little is known about the effects of chronic hypoxaemia or hypoglycaemia on the circulating levels of beta-endorphin and related polypeptides in the fetus. Therefore we also measured immunoreactive beta-endorphin in blood plasma from fetal sheep in which growth retardation in association with restricted placental growth was produced by removal of endometrial caruncles before mating. Intra-uterine growth retardation was accompanied by chronic hypoglycaemia and chronic hypoxaemia in the fetuses. This was not associated with higher concentrations of beta-endorphin-like immunoreactivity in fetal arterial or umbilical venous plasma, but was accompanied by significantly increased placental extraction of fetal immunoreactive beta-endorphin from the umbilical circulation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Secretion of N-terminal pro-opiomelanocortin-derived peptides in response to acute haemorrhagic stress in conscious sheep

To determine whether peptides derived from the N-terminus of the corticotropin/melanotropin/endorphin precursor, pro-opiomelanocortin, are released into blood in response to acute haemorrhagic stress, we examined the effect of haemorrhage on plasma concentrations of immunoreactive gamma 3-melanotropin, beta-endorphin and cortisol. Plasma concentrations of immunoreactive gamma 3-melanotropin (mean +/- SEM) increased within 30 min of haemorrhage from 71.1 +/- 10.4 to 106.8 +/- 6.3 fmol/mL (p less than 0.01) and plasma cortisol increased from 16.2 +/- 3.8 to 85.9 +/- 22.4 pmol/mL (p less than 0.025). The changes in plasma immunoreactive gamma 3-melanotropin and beta-endorphin were positively correlated (p less than 0.025). This study shows that peptides derived from the N-terminus of pro-opiomelanocortin are co-secreted with the C-terminal peptide beta-endorphin during acute haemorrhagic stress in sheep.