Comparative effects of pollen limitation, floral traits and pollinators on reproductive success of Hedysarum scoparium Fisch. et Mey. in different habitats.

BACKGROUND: Reproduction in most flowering plants may be limited because of the decreased visitation or activity of pollinators in fragmented habitats. Hedysarum scoparium Fisch. et Mey. is an arid region shrub with ecological importance. We explored the pollen limitation and seed set of Hedysarum scoparium in fragmented and restored environments, and examined whether pollen limitation is a significant limiting factor for seed set. We also compared floral traits and pollinator visitation between both habitats, and we determined the difference of floral traits and pollinators influenced reproductive success in Hedysarum scoparium. RESULTS: Our results indicated that supplementation with pollen significantly increased seed set per flower, which is pollen-limited in this species. Furthermore, there was greater seed set of the hand cross-pollination group in the restored habitat compared to the fragmented environment. More visits by Apis mellifera were recorded in the restored habitats, which may explain the difference in seed production between the fragmented and restored habitats. CONCLUSIONS: In this study, a positive association between pollinator visitation frequency and open flower number was observed. The findings of this study are important for experimentally quantifying the effects of floral traits and pollinators on plant reproductive success in different habitats.

Overexpression of the PtSOS2 gene improves tolerance to salt stress in transgenic poplar plants.

In higher plants, the salt overly sensitive (SOS) signalling pathway plays a crucial role in maintaining ion homoeostasis and conferring salt tolerance under salinity condition. Previously, we functionally characterized the conserved SOS pathway in the woody plant Populus trichocarpa. In this study, we demonstrate that overexpression of the constitutively active form of PtSOS2 (PtSOS2TD), one of the key components of this pathway, significantly increased salt tolerance in aspen hybrid clone Shanxin Yang (Populus davidiana × Populus bolleana). Compared to the wild-type control, transgenic plants constitutively expressing PtSOS2TD exhibited more vigorous growth and produced greater biomass in the presence of high concentrations of NaCl. The improved salt tolerance was associated with a decreased Na(+) accumulation in the leaves of transgenic plants. Further analyses revealed that plasma membrane Na(+) /H(+) exchange activity and Na(+) efflux in transgenic plants were significantly higher than those in the wild-type plants. Moreover, transgenic plants showed improved capacity in scavenging reactive oxygen species (ROS) generated by salt stress. Taken together, our results suggest that PtSOS2 could serve as an ideal target gene to genetically engineer salt-tolerant trees.

Three new pyrrole alkaloids from the endophytic fungus Albifimbria viridis.

Three new pyrrole alkaloids albifipyrrols A-C (1-3), were isolated from the endophytic fungus Albifimbria viridis collected from the Chinese medicinal plant. Their structures were elucidated by extensive NMR and HRESIMS spectrometric analyses. All compounds were evaluated for immunosuppressive activity. Fortunately, compound 2 exhibits certain inhibition specifically against the LPS-induced proliferation of B lymphocyte cells with IC50 value 16.16 µM.

Paecilins F-P, new dimeric chromanones isolated from the endophytic fungus Xylaria curta E10, and structural revision of paecilin A.

A total of eleven new dimeric chromanones, paecilins F-P (2-12), were isolated from the endophytic fungus Xylaria curta E10, along with four known analogs (1, 13-15). Their structures and absolute configurations were determined by extensive experimental spectroscopic methods, single-crystal X-ray diffraction, and equivalent circulating density (ECD) calculations. In addition, the structure of paecilin A, which was reported to be a symmetric C8-C8' dimeric pattern, was revised by analysis of the nuclear magnetic resonance (NMR) data, and single-crystal X-ray diffraction. Compound 1 showed antifungal activity against the human pathogenic fungus Candida albicans with a minimum inhibitory concentration of 16 µg/mL, and Compounds 8 and 10 showed antibacterial activity against the gram-negative bacterium Escherichia coli with the same minimum inhibitory concentration of 16 µg/mL.

[Functional roles of the plant superoxide dismutase].

Superoxide Dismutases (SODs) are ubiquitously expressed antioxidant enzyme in aerobic organisms and catalyze dismutation of superoxide anion to hydrogen and molecular oxygen, the first step in active oxygen-scavenging systems. SODs play a central role in protecting cells against the toxic effects of reactive oxygen species generated during normal cellular metabolic activity or as a result of various environmental stresses. This paper reviews the expression and regulation of Sod genes and their functional role(s) during development and in response to stresses.