Does Lupinus angustifolius L. need sulfur fertilization under central European conditions?

In order to answer the question of whether narrow‐leaf lupin (Lupinus angustifolius L.) needs sulfur (S) fertilization under central European conditions, field trials were carried out at several sites in Germany on long‐term (> 10 years) organically cultivated arable land from 2012 to 2014. The effect of S‐containing fertilizers kieserite, gypsum, epsom salt, and elemental sulfur on S accumulation, yield, yield structure, and nitrogen (N) accumulation in narrow leaf lupin as well as the recovery of fertilized S was investigated. Under the given conditions, the fertilization did not influence seed yields. The S accumulation in shoots ranged from 11.8 kg ha^?1 to 14.1 kg ha^?1. The bulk of the absorbed S was accumulated in the straw (average S harvest index: 0.40). The N : S ratio in the youngest open leaf at BBCH 60–65 was about 20 and the corresponding S concentration was 0.24% in the leaf dry mass. The apparent recovery efficiency of S (RE) of kieserite, gypsum, and epsom salt, whose S form is generally plant‐available, was low with 4.0%, –2.1%, and 6.6%, respectively. The S requirement of the lupin was obviously completely filled by plant‐available S from the soil as well as atmospheric S deposition in all tested environments. Application of kieserite, gypsum, and epsom salt resulted in a partially significant increase in S concentration of seeds and straw, and also partly significantly narrowed the N : S ratios in the plants but did not increase yield. Application of elemental S did not lead to an increase in plant S concentration in the year of application.     

Antifeedant activity of luteolin and genistein against the pea aphid, Acyrthosiphon pisum

Electrical penetration graphs (DC EPG) were used to monitor the feeding behavior of the pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae) exposed to the flavonoids luteolin and genistein in artificial diets. The EPG patterns generated by aphids feeding on plants were used to interpret the patterns generated on the artificial diets. Addition of flavonoids to the diets generally prolonged the period of stylet probing (as indicated by EPG pattern d-C), reduced salivation (as indicated by pattern d-E1) and passive ingestion (as indicated by pattern d-E2), and also delayed the onset of salivation and passive ingestion. At higher concentrations (≥100?μg?cm^?3 for luteolin, ≥1,000?μg?cm^?3 for genistein), the flavonoids completely stopped salivation and passive ingestion. In most events associated with active ingestion (EPG pattern d-G), however, differences in feeding behavior did not statistically differ between the control diet and those with flavonoids; luteolin, and genistein only at 10?μg?cm^?3 prolonged the time until the first d-G pattern was observed. The current findings demonstrate detrimental effects of the isoflavone genistein and the flavone luteolin on the feeding behavior of the pea aphid, A. pisum. This can be employed to create plants which are resistant to aphids and other herbivores.     

Impact of tourism on the vigilance behavior of the Cyprus rock agama (Laudakia cypriaca)

Escape behavior is a common antipredator strategy among wild animals. Here, we investigated the effect of four factors on the vigilance behavior of the endemic Cyprus rock agama (Laudakia cypriaca). Flight initiation distance (FID, the minimum distance to which an observer can approach a lizard before it flees) was measured in relation to the type of location (tourist vs. nontourist area), the observer's starting distance, air temperature, and substrate temperature. We collected data for 39 agamas in tourist areas and 34 of these lizards in nontourist areas. As a whole, the mean starting distance was 10.5 m and the FID was 3.6 m. The average substrate temperature was 34.0°C and the average air temperature 29.6°C. Only the type of area affected the agamas’ escape decisions with FID being 1.8 m shorter in tourist areas than in nontourist areas (2.7 m vs. 4.5 m). This is probably due to the habituation of lizards to the presence of humans in the former areas. This study shows that tourism strongly affects the behavior of lizards, which may have consequences for the functioning of the population. Tourists can increase the safety of lizards by creating a human shield to deter predators. Once the tourist season is over, lizards may become more vulnerable to predators.     

From trees to fleas: masting indirectly affects flea abundance on a rodent host

Mast seeding causes strong fluctuations in populations of forest animals. Thus, this phenomenon can be used as a natural experiment to examine how variation in host abundance affects parasite loads. We investigated fleas infesting yellow-necked mice in beech forest after 2 mast and 2 non-mast years. We tested 2 mutually exclusive scenarios: (1) as predicted by classical models of density-dependent transmission, an increase in host density will cause an increase in ectoparasite abundance (defined as the number of parasites per host), versus (2) an increase in host density will cause a decline in flea abundance (“dilution,” which is thought to occur when parasite population growth is slower than that of the host). In addition, we assessed whether masting alters the relationship between host traits (sex and body mass) and flea abundance. We found a hump-shaped relationship between host and flea abundance. Thus, the most basic predictions are too simple to describe ectoparasite dynamics in this system. In addition, masting modified seasonal dynamics of flea abundance, but did not affect the relationship between host traits and flea abundance (individuals with the highest body mass hosted the most fleas; after controlling for body mass, parasite abundance did not vary between sexes). Our results demonstrate that pulses of tree reproduction can indirectly, through changes in host densities, drive patterns of ectoparasite infestation.     

Impacts of soil conditions and light availability on natural regeneration of Norway spruce <Emphasis Type="Italic">Picea abies</Emphasis> (L.) H. Karst. in low-elevation mountain forests

? Key message

Natural regeneration of P. abies (L.) H. Karst. may reach high densities in lower mountain elevations. The highest densities were found in sites with moderate light availability, with low pH, and not near the riverbank. However, age-height classes differed in the predicted magnitude of response, but were consistent in response directions. Mosses and understory species typical of coniferous forests were positively correlated with regeneration density.

? Context

Norway spruce Picea abies (L.) H. Karst. in Central Europe is at risk under climate change scenarios, particularly in mountain regions. Little is known about the impact of environmental factors on the natural regeneration of P. abies in low-elevation mountain forests.

? Aims

We aimed to assess impacts of distance from the riverbank, soil pH, and light availability on natural P. abies regeneration. We hypothesized that (1) natural P. abies regeneration would depend on light availability and soil pH and (2) there are understory plant species which may indicate the microsites suitable for natural regeneration of P. abies.

? Methods

The study was conducted in the Sto?owe Mountains National Park (SW Poland, 600–800 m a.s.l.). We established 160 study plots (25 m²) for natural regeneration, light availability, soil pH, and understory vegetation assessment.

? Results

The highest densities of natural regeneration of P. abies were observed in sites with moderate light availability (0.1–0.2 of open sky) and low pH (3.5–4.5), and located relatively far from the riverbank. Cover of 22 understory plant species were correlated with natural P. abies regeneration densities, mostly positively.

? Conclusion

Different stages of natural regeneration of P. abies revealed different regeneration niches. Most understory plant species (bryophytes and herbs typical of coniferous forests) do not compete with natural regeneration of P. abies.

     

The origin of clones among androgenic regenerants of hexaploid triticale

Doubled haploids (DH) have become a standard tool in breeding and genetic studies of many crops and in most cases androgenesis is the only available route of their production. It has been recently observed that some populations of DH lines obtained via androgenesis contain high proportions of clones. This seriously reduces the efficiency of breeding and may jeopardize genetic studies. This study was designed to determine at which stage of androgenesis these clones are created, using samples set aside during routine production of DH lines in breeding of hexaploid triticale. The fate of each androgenic structure was carefully followed through the entire regeneration process, and all obtained plants were genotyped using DNA markers. Overall, 189 plants were regenerated forming 33 families, each originating from a single original androgenic structure (callus, polyembryos). In ca. 80 % of cases all members of a family were genetically identical. However, in about 20 % of cases the families of regenerants were genetically heterogeneous, showing that not all androgenic structures originate from single microspores. The evidence shown here demonstrates that retention of single plants from each original structure guarantees the production of only unique genotypes but it reduces the total output of plants. If maximum output is desired, multiple regenerants from single callus can be retained but must be genotyped using at least 10 polymorphic markers to identify clones.     

Growth in juvenile pikeperch (Sander lucioperca L.) stimulated with yeast,Saccharomyces cerevisiae,extract

Thanks to the content of valuable bioactive substances, yeast, Saccharomyces cerevisiae, is finding wider applications in aquaculture and marine fish husbandry. Highly bio‐available and bio‐assimilable yeast extracts, which are obtained through processes that remove cell walls, are of special interest. The current study examined the impact of yeast extracts added to commercial feed at concentrations of 2% (group F2), 4% (group F4) and 6% (group F6) on growth, blood biochemistry parameters, liver and intestinal morphology, proximate body composition and the content of free amino acids in the muscle tissues of European pikeperch, Sander lucioperca (initial body weight = 10 g). At the termination of the experiment that ran for 60 days, the highest increases in body weight were noted in all the groups of fish that had received yeast extract (final body weight ≈ 35 g vs. control group ≈ 31 g). The daily and specific growth rates indexes were the highest in group F6. The alanine aminotransferase activity in this group was half of that in the control group (group C) (p < .05). The lowest levels of plasma bilirubin were noted in groups F4 and F6, while these groups had the highest hepatosomatic indexes that differed significantly to those of group C (p < .05). Microscopic analysis of the intestines indicated significant growth in the enterocyte height and supranuclear zone, or the so‐called absorption space, as the quantity of yeast extract added to the diets increased. Yeast supplementation was not noted to have a significant impact on the proximate body composition or the contents of free amino acids in the fish muscle tissues. In conclusion, the lowest analysed dose of yeast (i.e. 2% yeast extract) stimulates the growth of pikeperch.     

Tannic acid and Norway spruce condensed tannins can precipitate various organic nitrogen compounds

There is increasing evidence that tannins affect degradation of soil organic matter and nitrogen cycling. It is assumed that the influence of tannins on biochemical processes is partly related to their ability to precipitate proteins. However, there is almost no information about precipitation of organic nitrogen-containing compounds other than proteins. A few studies indicate that tannins can precipitate arginine, choline or chitosan. In this study we used commercial tannic acid and condensed tannins extracted from Norway spruce (Picea abies (L.) Karst) needles to investigate precipitation of a wide range of organic nitrogen compounds including amino acids (all 20 proteinaceous), peptides (insulin, oxidized glutathion, reduced glutathion, AlaAla, GlyGlu, GlyPhe, GlyGlyGly), proteins (bovine serum albumin, Rubisco i.e. d-ribulose 1,5-diphosphate carboxylase), nitrogen bases, polyamines and aminosugars (N-acetyl-d-glucosamine, chitin and chitosan). Our results showed that tannins can precipitate a subset of these compounds - of the amino acids only arginine, of the peptides studied only insulin, all the proteins, polyamines, nitrogen bases, chitin and chitosan, but not N-acetyl-d-glucosamine. Concentrations of organic nitrogen compound and tannins affected amount of these compounds in precipitates. Moreover, pH value affected precipitation. The amount of precipitated organic nitrogen compound and the amount of precipitated tannins showed positive correlation across different pH. Precipitation of organic N-containing compounds other than protein by tannins can potentially affect reactions in all biochemical mixtures including tannins and these organic nitrogen compounds, and affect soil N cycling.     

Influence of diterpenes (colophony and abietic acid) and a triterpene (beta-sitosterol) on net N mineralization,net nitrification,soil respiration,and microbial biomass in birch soil

The aim of this study was to examine the effect of common diterpenes (colophony, abietic acid) and triterpene (beta-sitosterol) on carbon (C) and nitrogen (N) transformations in soil under birch (Betula pendula L.). Samples were taken from the organic layer at two study sites, Kivalo (N-poor soil) and Kerimäki (N-rich soil), and incubated with the above-mentioned terpenes in laboratory conditions. Carbon dioxide evolution (C mineralization), net N mineralization, nitrification, and N and C in microbial biomass were measured. All these terpenes increased C mineralization, but decreased net N mineralization. The potential to decrease net N mineralization depended on amount of terpenes, with a stronger effect at a higher amount. Net nitrification in Kerimäki soil (N-rich soil) decreased but was not completely inhibited by terpenes. Effect of terpenes on soil microbial biomass C and N was not so clear, but they tended to increase both. Our study suggests that higher terpenes can act as a carbon source for soil microbial communities.