Variation in soil nitrifiers and leaf nitrate reductase activity of selected tree species in a forest community

Nitrate reductase activity of green leaves of red oak, hemlock, basswood, sugar maple and beech were studied in relation to soil ammonifier and nitrifier populations and available mineral N of associated soils in a forest community near Ithaca, New York. Significant intersite, i.e. interspecific, differences were found for all plant and soil factors studied. Extractable NH⁺₄-N was higher than NO₃⁻-N under all species. Nitrate reductase activities (NRA) of the green leaves of the five dominant species were significantly correlated with soil NO₃⁻-N beneath the tree canopies (P < 0.001). Nitrosomonas and Nilrobacter counts were intercorrelated (P < 0.001), and Nitrobacter was found to be related to both soil NH⁺₄ (P < 0.05) and soil NO⁻₃ (P < 0.001). Nitrosomonas and Nitrobacter counts were highest under basswood, and leaf NRA was 20–50 times higher in basswood leaves than in any of the other four species. Basswood also had the highest total leaf N, 5.02 ± 0.06%. Our data suggest that in these forest stands, green-leaf nitrate reductase activity is a reliable index of soil mineral N usage by the five species. Moreover, we believe that the data support the notion that Nitrobacter populations, and thus nitrification rates, are inhibited by the dominant tree species to result in a more ammonium-based nutrition, which on the system level ultimately has a conserving effect on the N economy of these stands.     

Importance of heat shock proteins in maize

Abiotic and biotic stress conditions cause extensive losses to maize production, mainly due to protein dysfunction in these conditions. In higher plants, the occurrence of heat-shock proteins (HSPs) in response to different environmental stresses is a universal phenomenon and has been well documented. Many studies have demonstrated that most HSPs are involved in many regulatory pathways, act as molecular chaperones for other cell proteins, and have strong cytoprotective effects. Although many functional roles for HSPs are known, the mechanisms for these multiple functions are not entirely understood. Here we reviewed the correlation among HSP genes/proteins and plant tolerance, especially maize, in different environmental stresses. Due to the low availability of information regarding the expression of HSP genes in response to different stresses in maize, we decided to mine databases in order to generate new insights related to this topic.     

Tracking Collembola feeding strategies by the natural C signal of fatty acids in an arable soil with different fertilizer regimes

Compound specific stable isotope analysis (¹³C/¹²C ratio of fatty acids) was used to assess the allocation of plant carbon in soil microbiota, and to identify the trophic links to microbial grazers in an arable field with long-term mineral and organic fertilizer amendments. The feeding strategy of two dominant Collembola species, epedaphic Isotoma viridis and euedaphic Willemia anophthalma was determined. The investigation was conducted following a shift to amaranth, a C₄ plant, after 27 years of continuous C₃ crop rotation. The influence of new C₄ plant carbon was observed in microbial phospholipids (PLFAs) with higher δ¹³C recorded in C₄ amaranth than in C₃ clover soils. The strongest enrichment occurred in the fungal PLFA 18:2ω6,9c and bacterial PLFA 18:1ω9t with 11.2‰ and 6.6‰, respectively. However, other bacterial PLFAs showed no isotopic change, suggesting that the microbial community simultaneously utilized “new” and “old” plant carbon. The δ¹³C of Collembola fatty acids displayed species specific lipid pattern, which was affected by crop type, but not fertilizer amendments. Isotopic separation of Collembola lipids from amaranth and clover plots was more distinct in I. viridis than W. anophthalma. With up to 18‰, the enrichment in Collembola lipids was stronger than in microbial PLFAs, pointing to a distinct incorporation of carbon resources originating from the actual plant residues. The δ¹³C pattern in I. viridis indicated trophic links with bacteria, saprotrophic fungi and plant tissues, while saprotrophic fungi and plant tissues were accountable for the patterns observed in W. anophthalma.     

Simplified performance assessment methodology for addressing soil quality of nature-based solutions

Journal of Soils and Sediments - In urban areas, soil functions are deeply impacted by all human activities, e.g., water infiltration, carbon storage, and chemical substances degradation potential....     

New trophic biomarkers for Collembola reared on algal diets

We used fatty acid (FA) analysis to investigate green algae and cyanobacteria as food sources for Collembola. We studied the effects of food quality on body mass and on neutral lipid (NLFA) and phospholipid (PLFA) fatty acid patterns of Collembola. Folsomia candida, Heteromurus nitidus and Protaphorura fimata were fed with common green algae (Chlorella vulgaris), filamentous soil algae (Klebsormidium flaccidum), cyanobacteria (Nostoc commune) and baker's yeast (Saccharomyces cerevisiae). Body mass of F. candida and H. nitidus was highest when reared on C. vulgaris and S. cerevisiae. P. fimata gained the most weight when fed baker's yeast. K. flaccidum and N. commune as resources resulted to low biomass in all Collembola. The four diets caused significant differences in the NLFA and PLFA composition of Collembola after six weeks of feeding. Two new trophic biomarker FAs indicating algal diets were assigned with 16:3ω3,6,9 and 16:2ω6,9, which were only present in NLFAs of Collembola consuming C. vulgaris and K. flaccidum. The amount of FAs from the ω7 family was high in Collembola lipids with cyanobacteria and yeast as food sources, whereas only trace amounts occurred in the NLFA fraction with algae as the resource. In summary, common soil algae and cyanobacteria differed in food quality for Collembola, depending on their growth form (unicellular versus filamentous) and/or secondary metabolites (e.g. cyanobacteria). The new FA biomarkers detected will allow further investigation of these trophic interactions under field conditions; for example, assessing the role of collembolan grazers in the formation of biological soil crusts.     

Evaluation of platinum distribution between different soil components

Purpose

More attention has been given to the determination of background levels of platinum group element (PGE) in an urban environment. But, few studies have been conducted for its environmental behaviour. The necessity to understand the PGE behaviour in environment increases due to the increase in platinum (Pt) emissions. The aim of the study is to evaluate the adsorption and the distribution of Pt within soil and sediment components. This study investigated the Pt adsorption on kaolinite, hematite and humic acid.

Materials and methods

A batch experiment was used to determine sorption of Pt. The experiments were carried out on the three solids and on two mixtures of iron oxide and kaolinite, with two ratios 25:75 and 75:25. An elemental distribution of Pt was determined on the mixtures iron oxide–kaolinite by micro-X-ray fluorescence.

Results and discussion

The highest concentrations of Pt were found on kaolinite, followed by hematite and humic acid. Kaolinite exhibited the highest adsorption capacity. The sorption capacity of both mixtures was lower than that of kaolinite and iron oxide. Moreover, the shape of isotherms, for both mixtures, tends towards that of kaolinite. The elemental distribution maps of mixtures showed, for both ratios, a high enrichment of kaolinite with Pt opposite to a slight enrichment of hematite.

Conclusions

The results showed that Pt is adsorbed mainly on kaolinite, which suggests that Pt was mainly associated with clay in soil. The results allowed the evaluation of the impact of the matrix of soil or sediment on the ability to retain or promote Pt dispersion in an urban environment.     

Influence of mitochondria origin on fruit quality in a citrus cybrid

Sugar, organic acid, and carotenoid are the most important indicators of fruit taste and nutritional and organoleptic quality. These components were studied on fruit pulp of the cybrid between Willow leaf mandarin ( Citrus deliciosa Ten.) and Eureka lemon [ Citrus limon (L.) Burm.] and the two parents. The cybrid possessed nuclear and chloroplast genomes of Eureka lemon plus mitochondria from Willow leaf mandarin. The impact of new mitochondria on fruit quality was studied during the mature period. Levels of organic acids were slightly higher in the cybrid fruit pulp than in Eureka lemon. No significant difference in sugar and carotenoid content was observed between the cybrid and the lemon. Results confirm that the main genetic information for the biosynthesis of sugars, organic acids, and carotenoids is contained in the nucleus. In Citrus, cybridization can be used as a strategy to breed specific traits associated with mitochondrial genomes, such as male sterility, without affecting the main organoleptic and nutritional qualities.     

Seasonal variations in the availability of fodder resources and practices of dairy cattle feeding among the smallholder farmers in Western Usambara Highlands,Tanzania

Tropical Animal Health and Production - The aim of this study was to assess the seasonal effects on quantity and quality of fodder resources and associated utilization practices among smallholder...