Effect of lead stress on mineral content and growth of wheat (Triticum aestivum) and spinach (Spinacia oleracea) seedlings

Lead (Pb) is the most common heavy metal contaminant in the environment. Pb is not an essential element for plants, but they absorb it when it is present in their environment, especially in rural areas when the soil is polluted by automotive exhaust and in fields contaminated with fertilizers containing heavy metal impurities. To investigate lead effects on nutrient uptake and metabolism, two plant species, spinach (Spinacia oleracea) and wheat (Triticum aestivum), were grown under hydroponic conditions and stressed with lead nitrate, Pb(NO₃)₂, at three concentrations (1.5, 3, and 15 mM).Lead is accumulated in a dose-dependent manner in both plant species, which results in reduced growth and lower uptake of all mineral ions tested. Total amounts and concentrations of most mineral ions (Na, K, Ca, P, Mg, Fe, Cu and Zn) are reduced, although Mn concentrations are increased, as its uptake is reduced less relative to the whole plant’s growth. The deficiency of mineral nutrients correlates in a strong decrease in the contents of chlorophylls a and b and proline in both species, but these effects are less pronounced in spinach than in wheat. By contrast, the effects of lead on soluble proteins differ between species; they are reduced in wheat at all lead concentrations, whereas they are increased in spinach, where their value peaks at 3 mM Pb.The relative lead uptake by spinach and wheat, and the different susceptibility of these two species to lead treatment are discussed.     

Altered profile of secondary metabolites in the root exudates of Arabidopsis ATP-binding cassette transporter mutants

Following recent indirect evidence suggesting a role for ATP-binding cassette (ABC) transporters in root exudation of phytochemicals, we identified 25 ABC transporter genes highly expressed in the root cells most likely to be involved in secretion processes. Of these 25 genes, we also selected six full-length ABC transporters and a half-size transporter for in-depth molecular and biochemical analyses. We compared the exuded root phytochemical profiles of these seven ABC transporter mutants to those of the wild type. There were three nonpolar phytochemicals missing in various ABC transporter mutants compared to the wild type when the samples were analyzed by high-performance liquid chromatography-mass spectrometry. These data suggest that more than one ABC transporter can be involved in the secretion of a given phytochemical and that a transporter can be involved in the secretion of more than one secondary metabolite. The primary and secondary metabolites present in the root exudates of the mutants were also analyzed by gas chromatography-mass spectrometry, which allowed for the identification of groups of compounds differentially found in some of the mutants compared to the wild type. For instance, the mutant Atpdr6 secreted a lower level of organic acids and Atmrp2 secreted a higher level of amino acids as compared to the wild type. We conclude that the release of phytochemicals by roots is partially controlled by ABC transporters.     

Prevalence of potentially pathogenic culturable bacteria on eggshells and in cloacae of female Pied Flycatchers in a temperate habitat in central Spain

ABSTRACT Bacteria grow on avian eggshells and thus can potentially cause diseases in developing embryos. Little is known about culturable bacteria colonizing avian eggshells in free‐living birds, with most studies restricted to poultry. Our objective was to examine the culturable bacterial array growing on eggshells during incubation that could negatively affect hatching success of Pied Flycatchers (Ficedula hypoleuca) in a temperate montane habitat in central Spain. Cloacal culturable bacteria of females were also analyzed because bacteria can be vertically transmitted from females to eggs. We used fecal samples as surrogates of cloacal samples due to the small size of sampled birds. We found that eggshells and female cloacae of Pied Flycatchers harbored 24 and 40 bacterial families and species, respectively, but only a few in each clutch and each cloaca. Rod‐shaped gram‐negative bacteria and bacteria in the family Pseudomonadaceae were the most common bacteria on eggshells during early and late incubation and in female cloacae. Although based on small sample sizes, we found that females with rod‐shaped gram‐negative bacteria in their cloacae laid eggs that also had these bacteria, providing possible evidence for vertical transmission. We found no evidence for vertical transmission of Pseudomonadaceae, suggesting a possible environmental source for these bacteria. The prevalence of bacterial morphological types and major taxonomical categories on eggshells did not vary from early to late stages of incubation, providing support for the hypothesis that incubation may have bacteriostatic effects on bacterial proliferation on eggshells. Despite being primary egg invaders in poultry, we detected no effects of culturable Pseudomonadaceae or Pseudomonas luteola on hatching success. Our study represents the first to examine the culturable bacteria growing on the eggshells of a wild bird in a temperate habitat and additional studies based on culture‐independent techniques are required to confirm our results.     

Cluster root formation and function vary in two species with contrasting geographic ranges

Plant and Soil - Southern South American Proteaceae can occupy soils that are rich in total phosphorus (P) but poor in available P (for example volcanic soils) thanks to their cluster roots (CR),...     

Comparative internal structure of dorsal lips and radiolar appendages in sabellidae (Polychaeta) and phylogenetic implications

Fan worms (Sabellidae) possess paired modified prostomial structures at the base of the radiolar crown, dorso‐lateral to the mouth, called dorsal lips. The dorsal lips are involved in the sorting of particles collected by the radiolar crown. The range of variation in the morphology of dorsal lips is extensive, and probably this is not only due to adaptations to different environments and feeding preferences but also due to phylogenetic constraints. In this study, we describe and compare the morphology of dorsal lips in a range of sabellid taxa based on histological cross‐sections of these structures, and compare our data and terminology with those of previous studies. Dorsal lips are maintained erect in most taxa by a modified radiole fused to them known as dorsal radiolar appendage. We suggest that dorsal radiolar appendages with an internal supporting axis (cellular or acellular) and probably also the ventral lips are synapomorphies of the family. J. Morphol., 2011. © 2010 Wiley‐Liss, Inc.