Reduction of Phytophthora Stem Rot Disease on Soybeans by the Application of CaCl2 and Ca(NO3)2

This study investigated the effect of CaCl₂ and Ca(NO₃)₂ on fungal growth of Phytophthora sojae isolates, disease reduction on two cultivars of Glycine max (L.) Merr. cv. Chusei‐Hikarikuro (black soybean) and cv. Sachiyutaka (white soybean) and zoospore release. A concentration of 20–30 mm CaCl₂ or 30 mm Ca(NO₃)₂ led to a slight decrease of the growth rate of two isolates on PDA; however, 0.4 and 4 mm of CaCl₂ and Ca(NO₃)₂ increased growth. The application of 4 mm CaCl₂ or more than 4 mm Ca(NO₃)₂ before inoculation greatly inhibited infection in the two soybean cultivars. Disease suppression recorded in laboratory experiments using pathogen mycelium was because of the response of plant tissues rather than a direct inhibition of pathogen hyphal growth by the application of calcium. Furthermore, Ca(NO₃)₂ was more effective than CaCl₂. The calcium contents in plants increased at the time of inoculation. The extent of disease reduction was related to an increased calcium uptake by plants of the two cultivars, except for some cases involving cv. Chusei‐Hikarikuro. Results showed that the effective element in reducing Phytophthora stem rot was calcium and that differences existed between the two cultivars in terms of the mechanisms of calcium uptake and the effect on disease suppression. The presence of 4–30 mm CaCl₂ and Ca(NO₃)₂ decreased the release of zoospores from isolates on lima bean agar, although 0.4 mm CaCl₂ and Ca(NO₃)₂ significantly induced zoospore release. These results suggest the possibility of applying a solution containing more than 4 mm of calcium to decrease the incidence of disease in agricultural fields by the inhibition of zoospore release.     

Enough space in a warmer world? Microhabitat diversity and small‐scale distribution of alpine plants on mountain summits

Aim

Global warming is predicted to shift distributions of mountain species upwards, driven by a release from climatic restrictions at their upper distribution limit and increased biotic pressure at their lower distribution limit. In alpine ecosystems, which are characterized by large microclimatic diversity and sparse vegetation cover, the relative importance of abiotic and biotic drivers for species distribution is poorly understood. To disentangle abiotic and biotic mechanisms affecting distributions of alpine species, we investigated how alpine plant species with differing elevational ranges and frequency trends over the past century differ in their microhabitat distribution, and how they respond to neighbouring vegetation.

Location

A total of 11 summits (2635—3410 m a.s.l.) in SE‐Switzerland.

Methods

We quantified the microscale abundance of 12 species in relation to biogeographic (frequency trend, i.e., change in occurrences over the past century, and elevational range on summits) and local microhabitat characteristics (temperature, substrate type). We assessed species size traits in relation to neighbouring vegetation characteristics to investigate possible neighbour interactions.

Results

Species with increasing frequency on summits over the past century were most abundant on scree and warmer slopes. Species with negative or stable frequency trends on summits were more abundant on organic soil and colder slopes. The preferred microhabitats of the latter were rarest overall, decreased with increasing elevation, and had the most competitive neighbours. Size of one high‐alpine specialist, Ranunculus glacialis was negatively related to cover of neighbouring vegetation, whereas other species showed no response to neighbours.

Main conclusions

Long‐term frequency trends of species correlate with their microhabitat association. Species with most negative frequency trends show preferences for the rarest microhabitat conditions, where they likely experience higher competitive pressure in a warming climate. This finding emphasizes the importance of characterizing microhabitat associations and microclimatic diversity to assess present and future distributions of alpine plant species.

     

Warming impacts on boreal fen CO2 exchange under wet and dry conditions

Northern peatlands form a major soil carbon (C) stock. With climate change, peatland C mineralization is expected to increase, which in turn would accelerate climate change. A particularity of peatlands is the importance of soil aeration, which regulates peatland functioning and likely modulates the responses to warming climate. Our aim is to assess the impacts of warming on a southern boreal and a sub‐arctic sedge fen carbon dioxide (CO₂) exchange under two plausible water table regimes: wet and moderately dry. We focused this study on minerotrophic treeless sedge fens, as they are common peatland types at boreal and (sub)arctic areas, which are expected to face the highest rates of climate warming. In addition, fens are expected to respond to environmental changes faster than the nutrient poor bogs. Our study confirmed that CO₂ exchange is more strongly affected by drying than warming. Experimental water level draw‐down (WLD) significantly increased gross photosynthesis and ecosystem respiration. Warming alone had insignificant impacts on the CO₂ exchange components, but when combined with WLD it further increased ecosystem respiration. In the southern fen, CO₂ uptake decreased due to WLD, which was amplified by warming, while at northern fen it remained stable. As a conclusion, our results suggest that a very small difference in the WLD may be decisive, whether the C sink of a fen decreases, or whether the system is able to adapt within its regime and maintain its functions. Moreover, the water table has a role in determining how much the increased temperature impacts the CO₂ exchange.     

Polygenic risk for schizophrenia,social dispositions,and pace of epigenetic aging: Results from the Young Finns Study

Schizophrenia is often regarded as a disorder of premature aging. We investigated (a) whether polygenic risk for schizophrenia (PRS_sch) relates to pace of epigenetic aging and (b) whether personal dispositions toward active and emotionally close relationships protect against accelerated epigenetic aging in individuals with high PRS_sch. The sample came from the population-based Young Finns Study (n = 1348). Epigenetic aging was measured with DNA methylation aging algorithms such as AgeAccel_Hannum, EEAA_Hannum, IEAA_Hannum, IEAA_Horvath, AgeAccel_Horvath, AgeAccel_Pheno, AgeAccel_Grim, and DunedinPACE. A PRS_sch was calculated using summary statistics from the most comprehensive genome-wide association study of schizophrenia to date. Social dispositions were assessed in terms of extraversion, sociability, reward dependence, cooperativeness, and attachment security. We found that PRS_sch did not have a statistically significant effect on any studied indicator of epigenetic aging. Instead, PRS_sch had a significant interaction with reward dependence (p = 0.001–0.004), cooperation (p = 0.009–0.020), extraversion (p = 0.019–0.041), sociability (p = 0.003–0.016), and attachment security (p = 0.007–0.014) in predicting AgeAccel_Hannum, EEAA_Hannum, or IEAA_Hannum. Specifically, participants with high PRS_sch appeared to display accelerated epigenetic aging at higher (vs. lower) levels of extraversion, sociability, attachment security, reward dependence, and cooperativeness. A rather opposite pattern was evident for those with low PRS_sch. No such interactions were evident when predicting the other indicators of epigenetic aging. In conclusion, against our hypothesis, frequent social interactions may relate to accelerated epigenetic aging in individuals at risk for psychosis. We speculate that this may be explained by social-cognitive impairments (perceiving social situations as overwhelming or excessively arousing) or ending up in less supportive or deviant social groups.     

Effect of Plasterboard Composition on Stachybotrys chartarum Growth and Biological Activity of Spores

The effects of plasterboard composition on the growth and sporulation of Stachybotrys chartarum as well as on the inflammatory potential of the spores were studied. S. chartarum was grown on 13 modified plasterboards under saturated humidity conditions. The biomass was estimated by measuring the ergosterol content of the S. chartarum culture while the spore-induced cytotoxicity and production of nitric oxide (NO), tumor necrosis factor alpha (TNF-α), and interleukin-6 in mouse macrophages was used to illustrate the bioactivity of spores. The ergosterol content of S. chartarum correlated with the number of spores collected from plasterboards. The growth and sporulation decreased compared to that of the reference board in those cases where (i) the liner was treated with biocide, (ii) starch was removed from the plasterboard, or (iii) desulfurization gypsum was used in the core. Spores collected from all the plasterboards were toxic to the macrophages. The biocide added to the core did not reduce the growth; in fact, the spores collected from that board evoked the highest cytotoxicity. The conventional additives used in the core had inhibitory effects on growth. Recycled plasterboards used in the core and the board lacking the starch triggered spore-induced TNF-α production in macrophages. In summary, this study shows that the growth of a strain of S. chartarum on plasterboard and the subsequent bioactivity of spores were affected by minor changes to the composition of the core or liners, but it could not be totally prevented without resorting to the use of biocides. However, incomplete prevention of microbial growth by biocides even increased the cytotoxic potential of the spores.     

Long-term effects of boron and copper on phenolics and monoterpenes in Scots pine (Pinus sylvestris L.) needles

Backgroud and aims

Plant boron (B) status is known to affect plant secondary metabolites but most studies have been short termed and in controlled environments. Copper (Cu) effects on phenolics are better known at toxic than at low levels. Here, the chemistry of Scots pine (Pinus sylvestris L.) needles was studied 20 years after fertilisation with B and Cu in a long-term field experiment on a drained boreal peatland.

Methods

Phenolic compounds were analysed from three needle year classes using high performance liquid chromatography (HPLC) and condensed tannins with modified acid-butanol assay. Monoterpenes in the youngest needles were analysed by gas chromatography–mass spectrometry (GC–MS).

Results

Needle B concentrations were at deficient level in controls (5.7 μg g^?1), but at the optimum level (12 μg g^?1) still 20 years after fertilisation. Copper concentrations were low but not deficient (4.0 μg g^?1 in unfertilised, 4.8 μg g^?1 in fertilised). Needle ageing increased the concentrations of individual phenolics in most cases, but decreased the concentration of condensed tannins. The concentrations of several individual phenolics were reduced by B fertilisation compared to B-deficient control, significantly in the cases of (+)-catechin and a neolignan. The concentrations of eight compounds and the sum of small-molecule phenolics were higher in Cu fertilised trees. Condensed tannins and monoterpenes were not affected by the micronutrients.

Conclusions

Boron and copper additions affected mostly the same phenolic compounds, but B decreased while Cu increased their concentrations, Cu effects being clearer. The higher phenolic concentrations in B deficient trees were not likely large enough to explain leader dieback in B-deficient trees. The effects and interactions of these micronutrients need to be further studied in field conditions to establish firstly if the changes in phenolics are consistent among species, and secondly what mechanisms lead to the changes. Although small, the changes in phenolic concentrations may affect the interactions of the trees with their biotic and abiotic environment, when consistent over many years.     

Effect of wood ash and nitrogen fertilization on soil chemical properties, soil microbial processes, and stand growth in two coniferous stands in Finland

The aim of our study was to investigate long-term effects of wood ash fertilization, given together with nitrogen, on soil chemical properties, soil microbiological processes related to C and N cycling, and tree growth. The study was carried out in a 31-year-old Scots pine stand and in a 45-year-old Norway spruce stand 15 years after application. The treatments were (1) a control with no ash or nutrient addition, (2) wood ash + N (WAN), and (3) a stand-specific fertilization (SSF) formulated on the basis of analyses carried out on needle and soil samples taken from the stand. The SSF treatments included N, Cu and B, and in the spruce stand also P. WAN decreased acidity and increased the extractable Ca, Mg and P concentrations in the organic layer in both stands, but SSF had no effect. The microbial processes reacted more strongly to the treatments in the pine stand, whereas the growth response, although only relatively slight during the third 5-year period after fertilization, was detected only in the spruce stand. WAN increased the NH₄-N concentrations in the organic layer compared to the control and SSF treatments on both sites. In the pine stand, amount of N in microbial biomass and both the C and net N mineralization rates were significantly higher in the WAN treatment than in the SSF treatment. On both sites net nitrification was negligible in all treatments. Soil microbial biomass, microbial respiration and N availability have been used as indices for assessing the biological activity and health of soil, and these parameters either increased or were not affected by the WAN treatment. Hence, with regard to these parameters there are justifiable grounds for applying wood ash.