Photosynthesis,Transpiration, and Water Use Efficiency of Vegetative and Reproductive Shoots of Grassland Species from North-Eastern China

The differences in net photosynthetic rate (P _N), transpiration rate (E), and water use efficiency (WUE) between the vegetative and reproductive shoots of three native grass species from the grassland of northeastern China [grey-green and yellow green populations of Leymus chinensis (Trin.) Tzvel., Puccinellia tenuiflora (Griseb) Scrib & Merr, Puccinellia chinampoensis Ohwi] were compared. The two type shoots experienced similar habitats, but differed in leaf life-span and leaf area. The leaf P _N and WUE for the vegetative shoots were significantly higher than those for the reproductive shoots in the grasses, while their E were remarked lower in the dry season. Relative lower leaf P _N and WUE for the reproductive shoots of grassland grasses may explain the facts of lower seed production and the subordinate role of seed in the grassland renewal in north-eastern China.     

Hymenolepis diminuta: Worm loss and worm weight loss in long-term infections of the rat

Infections of one and two Hymenolepis diminuta established in newly weaned rats continued to grow for the duration of the experiment (238 days), whereas infections of 5 worms per rat became asymptotic around Day 55 postinfection and remained at or below this level thereafter as shown by biomass and mean weight per worm measurements. Infections of 50 worms established in newly weaned rats became asymptotic around Day 28 postinfection and thereafter worms were lost from the rats. Initially the biomass fell with the loss of worms, but by Day 56 a new lower biomass persisted for the remainder of the infection period. This level was maintained, despite diminishing numbers of worms, due to the growth of surviving individuals to a weight exceeding the original weight at maturity by a factor of more than 2. Experiments using rats that were mature at the time of infection demonstrated that the same response occurred, but approximately 3 weeks earlier.     

Biochemistry and genetics of taste- and odor-producing cyanobacteria

Cyanobacteria are one of the principal sources of volatile organic compounds (VOCs) which cause offensive taste and odor (T&O) in drinking and recreational water, fish, shellfish and other seafood. Although non-toxic to humans, these T&O compounds severely undermine public trust in these commodities, resulting in substantial costs in treatment, and lost revenue to drinking water, aquaculture, food and beverage and tourist/hospitality industries. Mitigation and control have been hindered by the complexity of the communities and processes which produce and modify T&O events, making it difficult to source-track the major producer(s) and the factors governing VOC production and fate. Over the past decade, however, advances in bioinformatics, enzymology, and applied detection technologies have greatly enhanced our understanding of the pathways, the enzymes and the genetic coding for some of the most problematic VOCs produced by cyanobacteria. This has led to the development of tools for rapid and sensitive detection and monitoring for the VOC production at source, and provided the basis for further diagnostics of endogenous and exogenous controls. This review provides an overview of current knowledge of the major cyanobacterial VOCs, the producers, the biochemistry and the genetics and highlight the current applications and further research needs in this area.     

Species loss leads to community closure

Global extinction of a species is sadly irreversible. At a local scale, however, extinctions may be followed by re-invasion. We here show that this is not necessarily the case and that an ecological community may close its doors for re-invasion of species lost from it. Previous studies of how communities are assembled have shown that there may be rules for that process and that limitations are set to the order by which species are introduced and put together. Instead of focusing on the assembly process we randomly generated simple competitive model communities that were stable and allowed for two to 10 coexisting species. When a randomly selected single species was removed from the community, the cascading species loss was recorded and frequently the resulting community was more than halved. Cascading extinctions have previously been recorded, but we here show that the relative magnitude of the cascade is dependent on community size (and not only trophic structure) and that the reintroduction of the original species lost often is impossible. Hence, species loss does not simply leave a void potentially refilled, but permanently alters the entire community structure and consequently the adaptive landscape for potential re-invaders.     

Resprouting in the Mediterranean‐type shrub Erica australis afffected by soil resource availability

Abstract. Soil resource availability may affect plant regeneration by resprouting in disturbed environments directly, by affecting plant growth rates, or indirectly by determining allocation to storage in the resprouting organs. Allocation to storage may be higher in stressful, low resource‐supply soils, but under such conditions plant growth rates may be lower. These factors could act in opposite directions leading to poorly known effects on resprouting. This paper analyses the role played by soil resources in the production and growth of resprouts after removal of above‐ground plant tissues in the Mediterranean shrub Erica australis. At 13 sites, differing in substrate, we cut the base of the stems of six plants of E. australis and allowed them to resprout and grow for two years. Soils were chemically analysed and plant water potential measured during the summer at all sites to characterize soil resource availability. We used stepwise regression analysis to determine the relationships between the resprouting response [mean site values of the number of resprouts (RN), maximum length (RML) and biomass (RB)] and soil nutrient content and plant water potential at each site. During the first two years of resprouting there were statistically significant differences among sites in the variables characterizing the resprouting response. RML was always different among sites and had little relationship with lignotuber area. RN was less different among sites and was always positively correlated with lignotuber area. RB was different among sites after the two years of growth. During the first months of resprouting, RN and RML were highly and positively related to the water status of the plant during summer. At later dates soil fertility variables came into play, explaining significant amounts of variance of the resprouting variables. Soil extractable cations content was the main variable accounting for RML and RB. Our results indicate that resprout growth of E. australis is positively affected by high water availability at the beginning of the resprouting response and negatively so by high soil extractable cation content at later periods. Some of these factors had previously shown to be related, with an opposite sign, to the development of a relatively larger lignotuber. Indeed, RML and RB measured in the second year of resprouting were significantly and negatively correlated with some indices of biomass allocation to the lignotuber at each site. This indicates that sites favouring allocation to the resprouting organ may not favour resprout growth.     

Molecular Identification of Aeromonas and Coliform Bacteria Isolated on m Endo Media from Lake Erie Waters

Summary Bacteria from recreational waters collected from two Lake Erie beaches in Dunkirk, New York were plated onto m Endo LES media. The 16S rRNA gene was then amplified from coliform and non-coliform bacteria using the polymerase chain reaction. The PCR products were characterized by restriction fragment length polymorphism (RFLP) analysis. A total of 8 RFLP groups were identified from the analysis of 920 samples and selected PCR products from each group were sequenced. The DNA sequence analysis indicated that more than half of the bacteria identified as coliforms on the m Endo plates belonged to the genus Aeromonas from the family Aeromonadaceae. Most of the remaining coliforms were from the Enterobacteriaceae. The data indicate that m Endo agar plates allow the growth of non-coliform bacteria, especially Aeromonas species.     

Cyanobacteria passage through drinking water filters during perturbation episodes as a function of cell morphology, coagulant and initial filter loading rate

Eight pilot-scale in-line filtration trials were performed to evaluate the passage of cyanobacterial cells through drinking water filters after sudden increases in hydraulic loading rates. Trials were performed at 30 °C using two coagulant combinations (aluminum sulfate and cationic polymer or ferric chloride and cationic polymer), two initial filter loading rates (7 or 10 m/h) and two species of morphologically different cyanobacteria (Microcystis aeruginosa or Anabaena flos aquae). The filter was perturbed by instantaneously increasing the hydraulic loading rate by 50%. Filter influent and effluent water qualities were characterized by measuring turbidity, particles and chlorophyll a. The observed post-perturbation filter effluent chlorophyll a peaks were 1.6–48 times greater than the pre-perturbation averages. Chlorophyll a peaks were larger for M. aeruginosa than for A. flos aquae. Chlorophyll a peaks were also larger for the higher (10 m/h) than for the lower (7 m/h) initial filter loading rate. The post-perturbation effluent turbidity peaks were 1.4–7.2 times greater than the pre-perturbation averages. The post-perturbation effluent particle peaks were 6.5–25 times greater than the pre-perturbation averages. These results indicate that particles were a more sensitive indicator of cyanobacterial passage than turbidity.     

RNA‐seq analysis reveals new candidate genes for drip loss in a Pietrain × Duroc × Landrace × Yorkshire population

Drip loss, one of the most important meat quality traits, is characterized by low heritability. To date, the genetic factors affecting the drip loss trait have not been clearly elucidated. The objective of this study was to identify critical candidate genes affecting drip loss. First, we generated a Pietrain × Duroc × Landrace × Yorkshire commercial pig population and obtained phenotypic values for the drip loss trait. Furthermore, we constructed two RNA libraries from pooled samples of longissimus dorsi muscles with the highest (H group) and lowest (L group) drip loss and identified the differentially expressed genes (DEGs) between these extreme phenotypes using RNA‐seq technology. In total, 25 883 genes were detected in the H and L group libraries, and none was specifically expressed in only one library. Comparative analysis of gene expression levels found that 150 genes were differentially expressed, of which 127 were upregulated and 23 were downregulated in the H group relative to the L group. In addition, 68 drip loss quantitative trait loci (QTL) overlapping with 63 DEGs were identified, and these QTL were distributed mainly on chromosomes 1, 2, 5 and 6. Interestingly, the triadin (TRDN) gene, which is involved in muscle contraction and fat deposition, and the myostatin (MSTN) gene, which has a role in muscle growth, were localized to more than two drip loss QTL, suggesting that both are critical candidate genes responsible for drip loss.     

Effects of global environmental change on carbon partitioning in vegetative plants of Triticum aestivum and closely related Aegilops species

The use of fossil fuel is predicted to cause an increase of the atmospheric CO₂ concentration, which will affect the global pattern of temperature and precipitation. It is therefore essential to incorporate effects of temperature and water supply on carbon partitioning of plants to predict effects of elevated [CO₂] on growth and yield of Triticum aestivum. Although earlier papers have emphasized that elevated [CO₂] favours investment of biomass in roots relative to that in leaves, it has now become clear that these are indirect effects, due to the more rapid depletion of nutrients in the root environment as a consequence of enhanced growth. Broadly generalized, the effect of temperature on biomass allocation in the vegetative stage is that the relative investment of biomass in roots is lowest at a certain optimum temperature and increases at both higher and lower temperatures. This is found not only when the temperature of the entire plant is varied, but also when only root temperature is changed whilst shoot temperature is kept constant. Effects of temperature on the allocation pattern can be explained largely by the effect of root temperature on the roots' capacity to transport water. Effects of a shortage in water supply on carbon partitioning are unambiguous: roots receive relatively more carbon. The pattern of biomass allocation in the vegetative stage and variation in water-use efficiency are prime factors determining a plant's potential for early growth and yield in different environments. In a comparison of a range of T. aestivum cultivars, a high water-use efficiency at the plant level correlates positively with a large investment in both leaf and root biomass, a low stomatal conductance and a large investment in photosynthetic capacity. We also present evidence that a lower investment of biomass in roots is not only associated with lower respiratory costs for root growth, but also with lower specific costs for ion uptake. We suggest the combination of a number of traits in future wheat cultivars, i.e. a high investment of biomass in leaves, which have a low stomatal conductance and a high photosynthetic capacity, and a low investment of biomass in roots, which have low respiratory costs. Such cultivars are considered highly appropriate in a future world, especially in the dryer regions. Although variation for the desired traits already exists among wheat cultivars, it is much larger among wild Aegilops species, which can readily be crossed with T. aestivum. Such wild relatives may be exploited to develop new wheat cultivars well-adapted to changed climatic conditions.