Respiration and annual fungal production associated with decomposing leaf litter in two streams

1. We compared fungal biomass, production and microbial respiration associated with decomposing leaves in one softwater stream (Payne Creek) and one hardwater stream (Lindsey Spring Branch). 2. Both streams received similar annual leaf litter fall (478–492 g m^?2), but Lindsey Spring Branch had higher average monthly standing crop of leaf litter (69 ± 24 g m^?2; mean ± SE) than Payne Creek (39 ± 9 g m^?2). 3. Leaves sampled from Lindsey Spring Branch contained a higher mean concentration of fungal biomass (71 ± 11 mg g^?1) than those from Payne Creek (54 ± 8 mg g^?1). Maximum spore concentrations in the water of Lindsay Spring Branch were also higher than those in Payne Creek. These results agreed with litterbag studies of red maple (Acer rubrum) leaves, which decomposed faster (decay rate of 0.014 versus 0.004 day^?1), exhibited higher maximum fungal biomass and had higher rates of fungal sporulation in Lindsey Spring Branch than in Payne Creek. 4. Rates of fungal production and respiration per g leaf were similar in the two streams, although rates of fungal production and respiration per square metre were higher in Lindsey Spring Branch than in Payne Creek because of the differences in leaf litter standing crop. 5. Annual fungal production was 16 ± 6 g m^?2 (mean ± 95% CI) in Payne Creek and 46 ± 25 g m^?2 in Lindsey Spring Branch. Measurements were taken through the autumn of 2 years to obtain an indication of inter‐year variability. Fungal production during October to January of the 2 years varied between 3 and 6 g m^?2 in Payne Creek and 7–27 g m^?2 in Lindsey Spring Branch. 6. Partial organic matter budgets constructed for both streams indicated that 3 ± 1% of leaf litter fall went into fungal production and 7 ± 2% was lost as respiration in Payne Creek. In Lindsey Spring Branch, fungal production accounted for 10 ± 5% of leaf litter fall and microbial respiration for 13 ± 9%.     

Seasonal drought and dry‐season irrigation influence leaf‐litter nutrients and soil enzymes in a moist,lowland forest in Panama

Abstract Climatic conditions should not hinder nutrient release from decomposing leaf‐litter (mineralization) in the humid tropics, even though many tropical forests experience drought lasting from several weeks to months. We used a dry‐season irrigation experiment to examine the effect of seasonal drought on nutrient concentrations in leaf‐fall and in decomposing leaf‐litter. In the experiment, soil in two 2.25‐ha plots of old‐growth lowland moist forest on Barro Colorado Island, Republic of Panama, was watered to maintain soil water potential at or above field capacity throughout the 4‐month dry season. Wet‐season leaf‐fall had greater concentrations of nitrogen (N, 13.5 mg g^?1) and calcium (Ca, 15.6 mg g^?1) and lower concentrations of sulfur (S, 2.51 mg g^?1) and potassium (K, 3.03 mg g^?1) than dry‐season leaf‐fall (N = 11.6 mg g^?1, Ca = 13.6 mg g^?1, S = 2.98 mg g^?1, K = 5.70 mg g^?1). Irrigation did not affect nutrient concentrations or nutrient return from forest trees to the forest floor annually (N = 18 g m^?2, phosphorus (P) = 1.06 g m^?2, S = 3.5 g m^?2, Ca = 18.9 g m^?2, magnesium = 6.5 g m^?2, K = 5.7 g m^?2). Nutrient mineralization rates were much greater during the wet season than the dry season, except for K, which did not vary seasonally. Nutrient residence times in forest‐floor material were longer in control plots than in irrigated plots, with values approximately equal to that for organic matter (210 in control plots vs 160 in irrigated plots). Calcium had the longest residence time. Forest‐floor material collected at the transition between seasons and incubated with or without leaching in the laboratory did not display large pulses in nutrient availability. Rather, microorganisms immobilized nutrients primarily during the wet season, unlike observations in tropical forests with longer dry seasons. Large amounts of P moved among different pools in forest‐floor material, apparently mediated by microorganisms. Arylsulfatase and phosphatase enzymes, which mineralize organically bound nutrients, had high activity throughout the dry season. Low soil moisture levels do not hinder nutrient cycling in this moist lowland forest.     

The Estimated Impact of Fungi on Nutrient Dynamics During Decomposition of Phragmites australis Leaf Sheaths and Stems

Decomposition of culms (sheaths and stems) of the emergent macrophyte Phragmites australis (common reed) was followed for 16 months in the litter layer of a brackish tidal marsh along the river Scheldt (the Netherlands). Stems and leaf sheaths were separately analyzed for mass loss, litter-associated fungal biomass (ergosterol), nutrient (N and P), and cell wall polymer concentrations (cellulose and lignin). The role of fungal biomass in litter nutrient dynamics was evaluated by estimating nutrient incorporation within the living fungal mass. After 1 year of standing stem decay, substantial fungal colonization was found. This corresponded to an overall fungal biomass of 49 ± 8.7 mg g⁻¹ dry mass. A vertical pattern of fungal colonization on stems in the canopy is suggested. The litter bag experiment showed that mass loss of stems was negligible during the first 6 months, whereas leaf sheaths lost almost 50% of their initial mass during that time. Exponential breakdown rates were −0.0039 ± 0.0004 and −0.0026 ± 0.0003 day⁻¹ for leaf sheaths and stems, respectively (excluding the initial lag period). In contrast to the stem tissue—which had no fungal colonization—leaf sheaths were heavily colonized by fungi (93 ± 10 mg fungal biomass g⁻¹ dry mass) prior to placement in the litter layer. Once being on the sediment surface, 30% of leaf sheath's associated fungal biomass was lost, but ergosterol concentrations recovered the following months. In the stems, fungal biomass increased steadily after an initial lag period to reach a maximal biomass of about 120 mg fungal biomass g⁻¹ dry mass for both plant parts at the end of the experiment. Fungal colonizers are considered to contain an important fraction of nutrients within the decaying plant matter. Fungal N incorporation was estimated to be 64 ± 13 and 102 ± 15% of total available N pool during decomposition for leaf sheaths and stems, respectively. Fungal P incorporation was estimated to be 37 ± 9 and 52 ± 15% of total available P during decomposition for leaf sheaths and stems, respectively. Furthermore, within the stem tissue, fungi are suggested to be active immobilizers of nutrients from the external environment because fungi were often estimated to contain more than 100% of the original nutrient stock.     

Bioreactor type affects the accumulation of phenolic acids and flavonoids in microshoot cultures of Schisandra chinensis (Turcz.) Baill.

Microshoots of the East Asian medicinal plant species Schisandra chinensis (Chinese magnolia vine) were grown in bioreactors characterized by different construction and cultivation mode. The tested systems included two continuous immersion systems—a cone-type bioreactor (CNB) and a cylindric tube bioreactor (CTB), a nutrient sprinkle bioreactor (NSB), and two temporary immersion systems (TIS)—RITA® and Plantform. Microshoots were grown for 30 and 60 days in the MS medium enriched with 1 mg l^?1 NAA and 3 mg l^?1 BA. The accumulation of two groups of phenolic compounds: phenolic acids and flavonoids in the bioreactor-grown S. chinensis biomass, was evaluated for the first time. In the microshoot extracts, seven phenolic acids: chlorogenic, gallic, p–hydroxybenzoic, protocatechuic, syringic, salicylic and vanillic, and three flavonoids: kaempferol, quercitrin and rutoside, were identified. The highest total amount of phenolic acids (46.68 mg 100 g^?1 DW) was recorded in the biomass maintained in the CNB for 30 days. The highest total content of flavonoids (29.02 mg 100 g^?1 DW) was found in the microshoots maintained in the NSB for 30 days. The predominant metabolites in all the tested systems were: gallic acid (up to 10.01 mg 100 g^?1 DW), protocatechuic acid (maximal concentration 16.30 mg 100 g^?1 DW), and quercitrin (highest content 21.00 mg 100 g^?1 DW).

     

Fungi on Leaf Blades of <Emphasis Type="Italic">Phragmites australis</Emphasis> in a Brackish Tidal Marsh: Diversity,Succession, and Leaf Decomposition

Although fungi are known to colonize and decompose plant tissues in various environments, there is scanty information on fungal communities on wetland plants, their relation to microhabitat conditions, and their link to plant litter decomposition. We examined fungal diversity and succession on Phragmites australis leaves both attached to standing shoots and decaying in the litter layer of a brackish tidal marsh. Additionally, we followed changes in fungal biomass (ergosterol), leaf nitrogen dynamics, and litter mass loss on the sediment surface of the marsh. Thirty-five fungal taxa were recorded by direct observation of sporulation structures. Detrended correspondence analysis and cluster analysis revealed distinct communities of fungi sporulating in the three microhabitats examined (middle canopy, top canopy, and litter layer), and indicator species analysis identified a total of seven taxa characteristic of the identified subcommunities. High fungal biomass developed in decaying leaf blades attached to standing shoots, with a maximum ergosterol concentration of 548 ± 83 μg g^–1 ash-free dry mass (AFDM; mean ± SD). When dead leaves were incorporated in the litter layer on the marsh surface, fungi experienced a sharp decline in biomass (to 191 ± 60 μg ergosterol g^–1 AFDM) and in the number of sporulation structures. Following a lag phase, species not previously detected began to sporulate. Leaves placed in litter bags on the sediment surface lost 50% of their initial AFDM within 7 months (k = −0.0035 day^–1) and only 21% of the original AFDM was left after 11 months. Fungal biomass accounted for up to 34 ± 7% of the total N in dead leaf blades on standing shoots, but to only 10 ± 4% in the litter layer. These data suggest that fungi are instrumental in N retention and leaf mass loss during leaf senescence and early aerial decay. However, during decomposition on the marsh surface, the importance of living fungal mass appears to diminish, particularly in N retention, although a significant fraction of total detrital N may remain associated with dead hyphae.     

Comparative study among Avicennia marina,Phragmites australis,and Moringa oleifera based ethanolic-extracts for their antimicrobial,antioxidant, and cytotoxic activities

Microbial resistance and other emerging health risk problems related to the side effects of synthetic drugs are the major factors that result in the research regarding natural products. Fruits, leaves, seeds, and oils-based phyto-constituents are the most important source of pharmaceutical products. Plant extract chemistry depends largely on species, plant components, solvent utilized, and extraction technique. This study was aimed to compare the ethanolic extracts of a mangrove plant, i.e., Avicennia marina (1E: Lower half of A. marina‘s pneumatophores, 2E: A. marina‘s leaves, 3E: Upper half of A. marina‘s pneumatophores, and 4E: A. marina‘s shoots), with non-mangrove plants, i.e., Phragmites australis (5E: P. australis‘s shoot), and Moringa oleifera (6E: M. oleifera‘s leaves) for their antimicrobial activities, total phenolic contents, antioxidant activity, and cytotoxicity potential. The antimicrobial activity assays were performed on gram-positive bacteria (i.e., Bacillus subtilis and Staphylococcus aureus), gram-negative bacteria (i.e., Escherichia coli, and Pseudomonas aeruginosa), and fungi (i.e., Aspergillus niger, Candida albicans, and Rhizopus spp.). We estimated antioxidant activity by TAC, DPPH, and FRAP assays, and the cytotoxicity was evaluated by MTT assay. The results of antimicrobial activities revealed that B. subtilis was the most sensitive to the tested plant extracts compared to S. aureus, while it only showed sensitivity to 6E and Imipenem. 5E and 6E showed statistically similar results against P. aeruginosa as compared to Ceftazidime. E. coli was the most resistant bacteria against tested plant extracts. Among the tested plant extracts, maximum inhibition activity was observed by 6E against A. niger (22 ± 0.57 mm), which was statistically similar to the response of 6E against C. albicans and 3E against Rhizopus spp. 2E did not show any activity against tested fungi. We found that 6E (208.54 ± 1.92 mg g^?1) contains maximum phenolic contents followed by 1E (159.42 ± 3.22 mg g^?1), 5E (131.08 ± 3.10 mg g^?1), 4E (i.e., 72.41 ± 2.96 mg g^?1), 3E (67.41 ± 1.68 mg g^?1), and 2E (48.72 ± 1.71 mg g^?1). The results depict a significant positive correlation between the phenolic contents and the antioxidant activities. As a result, phenolic content may be a natural antioxidant source.     

Estimation of fungal biomass in the decaying cones ofPinus densiflora

Fungal biomass in the decaying cones ofPinus densiflora was investigated. Leaching, immobilization and mobilization phases were recognized in the decomposition process of cones. Fungal biomass was estimated by the agar-film technique, using a conversion factor of 0.62 mg dry wt. mm⁻³ of hyphal volume to biomass and a factor of 2.5 for in-efficiencency of homogenization. The fungal biomass was 4.9±2.1 (mean±S.D.) mg dry wt. g⁻¹ dry matter in the cones on the tree, 11±6 mg g⁻¹ in the leaching phase, 19±7 mg g⁻¹ in the immobilization phase and 30±15 mg g⁻¹ in the mobilization phase. It significantly increased after cones had lain on the forest floor, and also in the immobilization phase. The latter result suggests that the fungal biomass contributed to the immobilization of nitrogen in the decomposition process. The ratio of ergosterol content to fungal biomass in the cones was 2.9–8.8 μg mg⁻¹ dry wt., lying in the range of 2–16 μg mg⁻¹ reported for mycelia. This suggested that the estimate of fungal biomass was reasonable. Reduction in this ratio with the dry weight loss in the cones suggested that the proportion of relatively active fungal biomass decreased with the progress of decomposition.     

Chlorella vulgaris as a lipid source: Cultivation on air and seawater‐simulating medium in a helicoidal photobioreactor

The freshwater microalga Chlorella vulgaris was cultured batchwise on the seawater‐simulating Schlösser medium either in a 1.1‐L‐working volume helicoidal photobioreactor (HeP) or Erlenmeyer flask (EF) as control and continuously supplying air as CO₂ source. In these systems, maximum biomass concentration reached 1.65 ± 0.17 g L^?1 and 1.25 ± 0.06 g L^?1, and maximum cell productivity 197.6 ± 20.4 mg L^?1 day^?1 and 160.8 ± 12.2 mg L^?1 day^?1, respectively. Compared to the Bold's Basal medium, commonly employed to cultivate this microorganism on a bench‐scale, the Schlösser medium ensured significant increases in all the growth parameters, namely maximum cell concentration (268% in EF and 126% in HeP), maximum biomass productivity (554% in EF and 72% in HeP), average specific growth rate (67% in EF and 42% in HeP), and maximum specific growth rate (233% in EF and 22% in HeP). The lipid fraction of biomass collected at the end of runs was analyzed in terms of both lipid content and fatty acid profile. It was found that the seawater‐simulating medium, despite of a 56–63% reduction of the overall biomass lipid content compared to the Bold's Basal one, led in HeP to significant increases in both the glycerides‐to‐total lipid ratio and polyunsaturated fatty acid content compared to the other conditions taken as an average. These results as a whole suggest that the HeP configuration could be a successful alternative to the present means to cultivate C. vulgaris as a lipid source. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:279–284, 2016     

Effects of sucrose and pH levels on in vitro shoot regeneration from leaf explants of <Emphasis Type="Italic">Bacopa monnieri</Emphasis> and accumulation of bacoside A in regenerated shoots

Brahmi (Bacopa monnieri) is an important medicinal plant mainly used for the treatment of neurological disorders and depression. Recent investigations revealed that bacoside A is major chemical component shown to be responsible for memory facilitating action of brahmi. The current investigation was carried out to assess the potential for increasing biomass and the concentration of bacoside A in the in vitro regenerated shoots by varying sucrose and pH levels of shoot regeneration medium. The leaf explants were cultured on the Murashige and Skoog (MS) medium supplemented with 2 mg l⁻¹ kinetin (KN) and with varying concentrations of sucrose (0, 1, 2, 3, 4, 5 and 6% at pH 5.8) and pH (4.5, 5.0, 5.5, 6.0 and 6.5 with 2% sucrose) with the objective of verifying the effects of sucrose and pH level on shoot regeneration and to verify the accumulation of bacoside A in the regenerated shoots. The shoot biomass increased (150.50 ± 2.84 shoots per explant, fresh wt 6.31 ± 0.12 g and dry wt 250 ± 5.00 mg) on the medium supplemented with 2% sucrose and pH which was set at 4.5. The results of HPLC analysis indicate that increase in sucrose concentration (0, 1, 2, 3, 4, 5 and 6% at pH 5.8) lead to decrease in the bacoside A content (39.51, 22.43, 13.05, 12.17, 10.73, 9.56 and 8.93 mg g⁻¹ dry wt, respectively) in regenerated shoots. These findings provide evidence that stressful condition of inadequate supply of carbon elevated synthesis of bacoside A in brahmi shoots. However, 2% sucrose is found suitable for biomass accumulation. Therefore, medium supplemented with 2% sucrose and pH set at 4.5 was found suitable for both biomass (6.31 ± 0.12 g fresh wt and 250 ± 5.00 mg dry wt) and bacoside A accumulation (13.09 mg g⁻¹ dry wt).     

Household energy and recycling of nutrients and carbon to the soil in integrated crop‐livestock farming systems: a case study in Kumbursa village,Central Highlands of Ethiopia

Soil amendment with organic wastes in the Highlands of Ethiopia has been greatly reduced by widespread use of dung cakes and crop residues as fuels. This study assessed the interaction between household energy and recycling of nutrients and carbon to the soil using household survey, focus group discussions, key informant interviews, direct observations and measurements between 2014 and 2015 in Kumbursa village (Central Highlands of Ethiopia). All surveyed households were entirely dependent on biomass fuel for cooking, with production and consumption rates directly related to wealth status, which significantly varied (P < 0.001) among three farm wealth groups (poor, medium and rich). Crop residues and dung cakes accounted for 80(±3)% by energy content and 85(±4)% by dry mass weight of total biomass fuel consumption. Mean losses were 59(±2) kg ha^?1 yr^?1 nitrogen (109(±8) kg yr^?1 per household), 13.9(±0.3) kg ha^?1 yr^?1 phosphorus (26(±2) kg yr^?1 per household), 79(±2) kg ha^?1 yr^?1 potassium (150(±11) kg yr^?1 per household) and 2100(±40) kg ha^?1 yr^?1 organic carbon (3000(±300) kg yr^?1 per household). Rich farmers lost significantly more carbon and nutrients in fuel than farmers in other wealth groups. However, these losses were spread over a larger area, so losses per land area were significantly higher for medium and poor than for rich farmers. This means that the land of poorer farmers is likely to become degraded more rapidly due to fuel limitations than that of rich farmers, so increasing the poverty gap. The estimated financial loss per household due to not using dung and crop residues as organic fertilizer was 162(±8) USSoil amendment with organic wastes in the Highlands of Ethiopia has been greatly reduced by widespread use of dung cakes and crop residues as fuels. This study assessed the interaction between household energy and recycling of nutrients and carbon to the soil using household survey, focus group discussions, key informant interviews, direct observations and measurements between 2014 and 2015 in Kumbursa village (Central Highlands of Ethiopia). All surveyed households were entirely dependent on biomass fuel for cooking, with production and consumption rates directly related to wealth status, which significantly varied (P < 0.001) among three farm wealth groups (poor, medium and rich). Crop residues and dung cakes accounted for 80(±3)% by energy content and 85(±4)% by dry mass weight of total biomass fuel consumption. Mean losses were 59(±2) kg ha^?1 yr^?1 nitrogen (109(±8) kg yr^?1 per household), 13.9(±0.3) kg ha^?1 yr^?1 phosphorus (26(±2) kg yr^?1 per household), 79(±2) kg ha^?1 yr^?1 potassium (150(±11) kg yr^?1 per household) and 2100(±40) kg ha^?1 yr^?1 organic carbon (3000(±300) kg yr^?1 per household). Rich farmers lost significantly more carbon and nutrients in fuel than farmers in other wealth groups. However, these losses were spread over a larger area, so losses per land area were significantly higher for medium and poor than for rich farmers. This means that the land of poorer farmers is likely to become degraded more rapidly due to fuel limitations than that of rich farmers, so increasing the poverty gap. The estimated financial loss per household due to not using dung and crop residues as organic fertilizer was 162(±8) US$ yr^?1. However, this is less than their value as fuels, which was 490(±20) US$ yr^?1. Therefore, farmers will only be persuaded to use these valuable assets as soil improvers if an alternative, cheaper fuel source can be found.     

Caloric content of plant species and its role in a Leymus chinensis steppe community of Inner Mongolia, China

The caloric contents of 42 species and their composition in a Leymus chinensis steppe community of Inner Mongolia, China were determined and analyzed based on the field experiment for 11 years. The caloric content (x ± SD) of aboveground parts of plant species varied from (13156 ± 1141) J·g^?1 (ash contained) to (18141 ± 527) J·g^?1. The average caloric content of all species was (16899 ± 840) J·g^?1 and the inter-specific CV (coefficient of variation) was 4.9%. Of all the species, Caragana microphylla had the highest caloric content (18142 J·g^?1). Grasses had a higher average caloric content ((17425 ± 291) J·g^?1) than forbs ((16734 ± 844)J·g^?1). When the herbaceous species were classified into subgroups according to life-form and growth-form, the order of average caloric contents, from high to low, was: tall grasses ((17717 ± 92) J·g^?1) > legume ((17228 ± 433) J·g^?1) > short grasses ((17250 ± 218) J·g^?1) > remaining forbs ((16784 ± 529) J·g^?1) > subshrubs ((16719 ± 69) J·g^?1) > annuals and biennials ((15911 ± 1759) J·g^?1). There was a positive correlation (P < 0.05) between the caloric contents of 42 species and their relative biomass in the community. When all species were classified into 3 groups according to their composition in the community, the average caloric contents, weighed by the species relative biomass, followed the order: dominant (17740 J·g^?1) > companion (17244 J·g^?1) > incidental (16653 J·g^?1). The plants with high caloric contents were more competitive, which allowed them to gain a dominant status, whereas the competitive abilities of plants with low caloric contents were generally weak. The latter made up the companion or incidental species in a steppe community.     

Non‐symbiotic nitrogen fixation during leaf litter decomposition in an old‐growth temperate rain forest of Chiloé Island,southern Chile: Effects of single versus mixed species litter

Heterotrophic nitrogen fixation is a key ecosystem process in unpolluted, temperate old‐growth forests of southern South America as a source of new nitrogen to ecosystems. Decomposing leaf litter is an energy‐rich substrate that favours the occurrence of this energy demanding process. Following the niche ‘complementarity hypothesis’, we expected that decomposing leaf litter of a single tree species would support lower rates of non‐symbiotic N fixation than mixed species litter taken from the forest floor. To test this hypothesis we measured acetylene reduction activity in the decomposing monospecific litter of three evergreen tree species (litter C/N ratios, 50–79) in an old‐growth rain forest of Chiloé Island, southern Chile. Results showed a significant effect of species and month (anova , Tukey's test, P < 0.05) on decomposition and acetylene reduction rates (ARR), and a species effect on C/N ratios and initial % N of decomposing leaf litter. The lowest litter quality was that of Nothofagus nitida (C/N ratio = 78.7, lignin % = 59.27 ± 4.09), which resulted in higher rates of acetylene reduction activity (mean = 34.09 ± SE = 10.34 nmol h^?1 g^?1) and a higher decomposition rate (k = 0.47) than Podocarpus nubigena (C/N = 54.4, lignin % = 40.31 ± 6.86, Mean ARR = 4.11 ± 0.71 nmol h^?1 g^?1, k = 0.29), and Drimys winteri (C/N = 50.6, lignin % = 45.49 ± 6.28, ARR = 10.2 ± 4.01 nmol h^?1 g^?1, k = 0.29), and mixed species litter (C/N = 60.7, ARR = 8.89 ± 2.13 nmol h^?1g^?1). We interpret these results as follows: in N‐poor litter and high lignin content of leaves (e.g. N. nitida) free‐living N fixers would be at competitive advantage over non‐fixers, thereby becoming more active. Lower ARR in mixed litter can be a consequence of a lower litter C/N ratio compared with single species litter. We also found a strong coupling between in situ acetylene reduction and net N mineralization in surface soils, suggesting that as soon N is fixed by diazotroph bacteria it may be immediately incorporated into mineral soil by N mineralizers, thus reducing N immobilization.     

Asparagus racemosus cell cultures: a source for enhanced production of shatavarins and sarsapogenin

Asparagus racemosus is an important monocot medicinal plant that is in great demand for its steroidal saponins called shatavarins. This study was initiated to optimize the conditions for production of shatavarins in cell cultures of A. racemosus in a modified Murashige and Skoog (MS) medium supplemented with six different combinations of growth regulators. Biomass accumulation was correlated with saponin production over a 30-d culture cycle. Biomass and saponin accumulation patterns were dependent on combinations of growth regulators and the pH of the medium. Maximum levels of saponin and biomass accumulation were recorded on day 25 of the culture cycle within a pH range of 3.4 to 5.6. Total saponin produced by the in vitro cultures was 20-fold higher than amounts produced by cultivated plants. Saponin accumulation was not a biomass-associated phenomenon; cultures which showed the highest biomass accumulation were not the highest saponin accumulators. Maximum biomass (28.30 ± 0.29 g l⁻¹) and maximum levels of shatavarin IV(11.48 ± 0.61 mg g⁻¹) accumulation was found using a medium containing 2.0 mg l⁻¹ 2,4-D, 2 g l⁻¹ casein hydrolysate and 0.005% pectinase. The highest levels of sarsapogenin, secreted and intracellular (4.02 ± 0.09 mg g⁻¹), accumulated using a medium containing 1.0 mg l⁻¹ NAA, 1.0 mg l⁻¹ 2,4-D, 0.5 mg l⁻¹ BAP, 2 g l⁻¹ casein hydrolysate and 0.005% pectinase, after 25 d. Shatavarins were secreted into the medium and can be isolated easily for further purification.     

Caloric content of plant species and its role in a Leymus chinensis steppe community of Inner Mongolia, China

The caloric contents of 42 species and their composition in a Leymus chinensis steppe community of Inner Mongolia, China were determined and analyzed based on the field experiment for 11 years. The caloric content (x ± SD) of aboveground parts of plant species varied from (13156 ± 1141) J·g^?1 (ash contained) to (18141 ± 527) J·g^?1. The average caloric content of all species was (16899 ± 840) J·g^?1 and the inter-specific CV (coefficient of variation) was 4.9%. Of all the species, Caragana microphylla had the highest caloric content (18142 J·g^?1). Grasses had a higher average caloric content ((17425 ± 291) J·g^?1) than forbs ((16734 ± 844)J·g^?1). When the herbaceous species were classified into subgroups according to life-form and growth-form, the order of average caloric contents, from high to low, was: tall grasses ((17717 ± 92) J·g^?1) > legume ((17228 ± 433) J·g^?1) > short grasses ((17250 ± 218) J·g^?1) > remaining forbs ((16784 ± 529) J·g^?1) > subshrubs ((16719 ± 69) J·g^?1) > annuals and biennials ((15911 ± 1759) J·g^?1). There was a positive correlation (P < 0.05) between the caloric contents of 42 species and their relative biomass in the community. When all species were classified into 3 groups according to their composition in the community, the average caloric contents, weighed by the species relative biomass, followed the order: dominant (17740 J·g^?1) > companion (17244 J·g^?1) > incidental (16653 J·g^?1). The plants with high caloric contents were more competitive, which allowed them to gain a dominant status, whereas the competitive abilities of plants with low caloric contents were generally weak. The latter made up the companion or incidental species in a steppe community.     

Use of the effluent from biogas production for cultivation of Spirulina

The effluent from the biogas process was tested as a nutrient source during cultivation of the protein-rich and edible microalgae Spirulina (Arthrospira platensis) and compared with conventional Spirulina medium. Equal biomass production was observed until late exponential phase and no significant differences could be observed between the treatments in protein amount, amino acid composition, and total lipid concentration. The concentration of the pigment phycocyanin differed significantly between Spirulina medium and the effluent-based medium (63.3 ± 11.7 and 86.2 ± 1.9 mg g⁻¹, respectively). Slightly higher concentrations of saturated fatty acids, mainly palmitic acid, were observed in the biomass produced in Spirulina medium than in that produced in the effluent-based medium. In the biomass produced in the effluent-based medium, the cadmium concentration was 0.07 ± 0.05 mg kg⁻¹ of dry weight, whereas it was below the detection limit in the biomass produced in Spirulina medium. There is a need to identify new food and feed resources and a possible future scenario is to integrate Spirulina production into the biogas plant for protein production as it contains more than 60% of protein on dry weight basis. In that scenario, it is important to control heavy metal concentrations in the biogas slurry fed to Spirulina.

     

Increased miroestrol, deoxymiroestrol and isoflavonoid accumulation in callus and cell suspension cultures of Pueraria candollei var. mirifica

Miroestrol and deoxymiroestrol are highly active phytoestrogens derived from the tuberous roots of Pueraria candollei var. mirifica. To date, there have been no reports regarding the production of miroestrol and deoxymiroestrol in in vitro cell culture. In this study, callus and cell suspension cultures were established for the purpose of investigating miroestrol and deoxymiroestrol content in P. candollei var. mirifica cells. Stem-derived callus cultured on Murashige and Skoog (MS) medium supplemented with 0.1 mg l⁻¹ thidiazuron (TDZ), 0.5 mg l⁻¹ naphthaleneacetic acid (NAA), and 1.0 mg l⁻¹ benzyladenine (BA) provided optimal conditions for the accumulation of deoxymiroestrol and total isoflavonoids. The calli produced 184.83 ± 20.09 μg g⁻¹ dry weight of total chromene and 20.72 ± 2.38 mg g⁻¹ dry weight of total isoflavonoid. This is the first report to suggest that callus culture is a suitable alternative method for producing miroestrol and deoxymiroestrol. Carbon sources were evaluated for the cell suspension cultures of P. candollei var. mirifica. Sucrose provided optimal conditions for biomass production, whereas fructose was the most suitable carbon source for deoxymiroestrol and isoflavonoid production. The information from our study can be employed for enhancing the production of miroestrol, deoxymiroestrol, and total isoflavonoids using in vitro cell culture of P. candollei var. mirifica.     

Nuclear internal transcribed spacer‐1 as a sensitive genetic marker for environmental DNA studies in common carp Cyprinus carpio

The recently developed environmental DNA (eDNA) analysis has been used to estimate the distribution of aquatic vertebrates by using mitochondrial DNA (mtDNA) as a genetic marker. However, mtDNA markers have certain drawbacks such as variable copy number and maternal inheritance. In this study, we investigated the potential of using nuclear DNA (ncDNA) as a more reliable genetic marker for eDNA analysis by using common carp (Cyprinus carpio). We measured the copy numbers of cytochrome b (CytB) gene region of mtDNA and internal transcribed spacer 1 (ITS1) region of ribosomal DNA of ncDNA in various carp tissues and then compared the detectability of these markers in eDNA samples. In the DNA extracted from the brain and gill tissues and intestinal contents, CytB was detected at 95.1 ± 10.7 (mean ± 1 standard error), 29.7 ± 1.59 and 24.0 ± 4.33 copies per cell, respectively, and ITS1 was detected at 1760 ± 343, 2880 ± 503 and 1910 ± 352 copies per cell, respectively. In the eDNA samples from mesocosm, pond and lake water, the copy numbers of ITS1 were about 160, 300 and 150 times higher than those of CytB, respectively. The minimum volume of pond water required for quantification was 33 and 100 mL for ITS1 and CytB, respectively. These results suggested that ITS1 is a more sensitive genetic marker for eDNA studies of C. carpio.     

Post‐fire carbon dynamics in the tropical peat swamp forests of Brunei reveal long‐term elevated CH4 flux

Tropical peatlands hold about 15%–19% of the global peat carbon (C) pool of which 77% is stored in the peat swamp forests (PSFs) of Southeast Asia. Nonetheless, these PSFs have been drained, exploited for timber and land for agriculture, leading to frequent fires in the region. The physico‐chemical characteristics of peat, as well as the hydrology of PSFs are affected after a fire, during which the ecosystem can act as a C source for decades, as C emissions to the atmosphere exceed photosynthesis. In this work, we studied the longer‐term impact of fires on C cycling in tropical PSFs, hence we quantified the magnitude and patterns of C loss (CO₂, CH₄ and dissolved organic carbon) and soil‐water quality characteristics in an intact and a degraded burnt PSF in Brunei Darussalam affected by seven fires over the last 40 years. We used natural tracers such as ¹⁴C to investigate the age and sources of C contributing to ecosystem respiration (R_eco) and CH₄, while we continuously monitored soil temperature and water table (WT) level from June 2017 to January 2019. Our results showed a major difference in the physico‐chemical parameters, which in turn affected C dynamics, especially CH₄. Methane effluxes were higher in fire‐affected areas (7.8 ± 2.2 mg CH₄ m^?2 hr^?1) compared to the intact PSF (4.0 ± 2.0 mg CH₄ m^?2 hr^?1) due to prolonged higher WT and more optimal methanogenesis conditions. On the other hand, we did not find significant differences in R_eco between burnt (432 ± 83 mg CO₂ m^?2 hr^?1) and intact PSF (359 ± 76 mg CO₂ m^?2 hr^?1). Radiocarbon analysis showed overall no significant difference between intact and burnt PSF with a modern signature for both CO₂ and CH₄ fluxes implying a microbial preference for the more labile C fraction in the peat matrix.     

Comparison of Methanotrophic Community and Methane Oxidation between Rhizospheric and Non-Rhizospheric Soils

Using particulate methane monooxygenase (pMMO) encoding gene, pmoA-based terminal-restrict fragment length polymorphism (T-RFLP), the methanotrophic communities between rhizospheric soils (RSs) and non-rhizospheric soil (NRSs) of landfill cover (LC), riparian wetland (RW) and rice paddy (RP) were compared before and after pre-incubation of 90 days. The ultimate potential of methane oxidation rate (UPMOR) and gene copy number of pmoA were evaluated in the soil samples after pre-incubation. Compared to the methanotrophic community in the soil samples before pre-incubation, type II methanotrophs, the Methylocystis-Methylosinus group, was mostly increased after pre-incubation, regardless of the soil type. The UPMOR (11.82 ± 0.27 μmol-CH₄· g^?1 _soil-DW·h^?1) in the LC-RS was significantly higher than that (9.57 ± 0.14 μmol-CH₄· g^?1 _soil-DW·h^?1) in the LC-NRS. However, no significant difference was found between RSs and NRSs in the RW (15.28 ± 0.91 and 13.23 ± 0.69 μmol-CH₄· g^?1 _soil-DW·h^?1, respectively) and RP (13.81 ± 1.04 and 12.81 ± 2.40 μmol-CH₄· g^?1 _soil-DW·h^?1, respectively) soils. There was no significantly difference in the gene copy numbers of pmoA in the RSs compared with those in the NRSs at all of the sampling sites. This study provides basic metagenomic information about both rhizospheric and non-rhizospheric methanotrophs, which will be helpful in developing a better strategy of biological methane removal from both natural and anthropogenic major methane sources.     

Nitrogen Translocation to Fresh Litter in Northern Hardwood Forest

Nitrogen immobilization in fresh litter represents a significant N flux in forest ecosystems, and changes in this process resulting from atmospheric N deposition could have important implications for ecosystem responses. We conducted two leaf decay experiments, using ¹⁵N-labeled sugar maple leaf litter, to quantify N transport from old litter and soil to fresh litter during early stages of decomposition, and we examined the influence of litter N concentration and soil N availability on upward N transfer in a northern hardwood forest. After one year of decay, the average N transfer from soil to fresh litter (2.63 mg N g^?1 litter) was much higher than the N transfer from older litter (1- to 2-years-old) to fresh litter (0.37 mg N g^?1 litter). We calculated the ratio of annual N transfer per unit of excess ¹⁵N pool for these two N sources. The ratio was not significantly different between old litter and soil, suggesting that fungi utilize N in the old litter and mineral soil pools for transport to decaying fresh litter with similar efficiency. Initial litter N concentration had a significant effect on upward N flux into decaying leaf litter, whereas no effect of soil N fertilization was observed. Reduction in the flux from soil to fresh litter owing to anthropogenic N inputs probably contributes significantly to changing soil N dynamics. Future work is needed on fungal N acquisition and transport as well as the fungal taxa involved in this process and their responses to changing environments.