Peat Substrate Research Articles

Low UV-B radiation and substrate acidity impact on photosynthetic parameters of Brassica napus

The aim of this study was to assess combined effect of 1 kJm-2d-1 UV-B radiation and substrate acidity (pH 4.8) on photosynthesis and growth of summer rape (Brassica napus) in a controlled environment. Rape were sown in a neutral (pH 6.0-6.5) peat substrate, when 2nd true leaf unfolded, growth substrate was acidified using 0.07 mM H2SO4 concentration solution and UV-B radiation exposure was started. Duration of the experiment: five days. Gas exchange parameters were measured with portable photosynthesis system LI-6400. Content of chlorophyll was evaluated spectrophotometrically. The results showed that the highest inhibition on Brassica napus growth and photosynthetic parameters was under combined effect of 1 kJm-2d-1 UV-B radiation and pH 4.8 substrate acidity. The impact of single 1 kJm-2d-1 UV-B radiation on investigated parameters was low and statistically insignificant, except transpiration rate and water use efficiency. Single substrate acidity affected in 58.6% (p < 0.05) decrease in photosynthetic rate, almost twofold decrease of transpiration rate, and 3.8% (p < 0.05) decrease in intercellular CO2 concentration, and 27.1% (p < 0.05) increase in water use efficiency, compared to the reference treatment. Combined substrate acidity and UV-B radiation effect on photosynthetic rate was the highest, when the decrease was 80.6% (p < 0.05), compared to the reference treatment. The changes of transpiration rate under combined effect of investigated stressors compared to the reference treatment were insignificant (p > 0.05). The increase (by 2%, p < 0.05) of intercellular CO2 concentration of Brassica napus affected by combined impact of investigated stressors shows that higher negative impact was on enzymatic reactions of photosynthesis than on transpiration. The highest negative effect on content of photosynthetic pigments and biomass accumulation also was of combined effect of investigated stressors.

CONSEQUENCES OF ROOT DEVELOPMENT ON THE EVOLUTION OF HYDRAULIC PROPERTIES OF PEAT GROWING MEDIA UNDER A CONSTANT AND OPTIMAL WATER REGIME

ISHS International Symposium on Growing Media, Composting and Substrate Analysis CONSEQUENCES OF ROOT DEVELOPMENT ON THE EVOLUTION OF HYDRAULIC PROPERTIES OF PEAT GROWING MEDIA UNDER A CONSTANT AND OPTIMAL WATER REGIME

In Vitro Propagation of Alexandrian Laurel (Danae racemosa L. Moench), a Valuable Ornamental Plant

To overcome the limitations of traditional propagation, this research was initiated to develop an alternative means for efficient production of Alexandrian laurel (Danae racemosa L. Moench). An in vitro propagation protocol has been developed for Danae racemosa L. Moench using seeds as a source of material for culture initiation. Seedlings were produced after seeds were cultured for 3 month on MS (Murashige and Skoog, 1962) medium. Shoot multiplication occurred on MS medium with or without 6-benzylaminopurine (BAP) with 100% multiplication percentage. However, shoot number was significantly increased from an average of 2.8 to more than six with the addition of 5 or 25 μM BAP. Among two indole-3-butyric acid (IBA) treatments tested for rooting of seedlings, incorporation of 5 μM IBA in MS medium significantly increased rooting percentage to 86.4% compared with 71.2% without IBA. The greatest number of roots (three) was produced by 5-minute IBA pulse. However, both IBA treatments significantly reduced root length. The longest root (12.8 mm) was observed on MS medium without any IBA treatment and the shortest (6.1 mm) was produced by IBA pulse. In vitro-propagated plantlets grew well after transfer to a substrate of peat and pine bark (1:1) in the greenhouse. No morphological variation was observed.

LED irradiance level affects growth and nutritional quality of Brassica microgreens

AbstractThis study examines the effect of irradiance level produced by solid-state light-emitting diodes (LEDs) on the growth, nutritional quality and antioxidant properties of Brassicaceae family microgreens. Kohlrabi (Brassica oleracea var. gongylodes, ‘Delicacy Purple’) mustard (Brassica juncea L., ‘Red Lion’), red pak choi (Brassica rapa var. chinensis, ‘Rubi F1’) and tatsoi (Brassica rapa var. rosularis) were grown using peat substrate in controlled-environment chambers until harvest time (10 days, 21/17°C, 16 h). A system of five lighting modules with 455, 638, 665 and 731 nm LEDs at a total photosynthetic photon flux densities (PPFD) of 545, 440, 330, 220 and 110 µmol m−2s−1 respectively were used. Insufficient levels of photosynthetically active photon flux (110 µmol m−2 s−1) suppressed normal growth and diminished the nutritional value of the Brassica microgreens studied. In general, the most suitable conditions for growth and nutritional quality of the microgreens was 330–440 µmol m−2 s−1 irradiation, which resulted in a larger leaf surface area, lower content of nitrates and higher total anthocyanins, total phenols and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging capacity. High light levels (545 µmol m−2 s−1), which was expected to induce mild photostress, had no significant positive impact for most of investigated parameters.

Manganese in substrate clays—harmful for plants?

AbstractMixtures of peat and substrate clays are commonly used as growth media for horticultural plant production. A quality protocol for substrate clays defines a threshold value of active manganese (Mnact = sum of exchangeable and easily reducible Mn) in substrate clays of < 500 mg kg–1 to prevent toxic reactions of plants. This threshold value was tested in experiments with peat‐clay blends under various growth conditions, and nutrient solution experiments were additionally conducted to investigate the effects of silicic acid and dissolved organic matter on the occurrence of Mn toxicity. Common bean (Phaseolus vulgaris L.) and hydrangea (Hydrangea macrophylla) plants were cultivated in different peat‐clay substrates and in peat under different moisture and pH levels. The clays varied in their Mnact content from 4–2354 mg kg–1. The results of the substrate experiments reveal that a threshold value for Mn in substrate clays is not justified, as plants grown in all peat‐clay substrates did not develop any Mn toxicity even at high substrate moisture or low pH conditions which are known to increase the Mn availability. The extraction of active Mn did not well reflect the Mn concentrations in plant dry matter and substrate solution. As plants tolerated high Mn concentrations in the substrate solution compared to the nutrient solution without toxicity symptoms, the influence of silicic acid and dissolved organic matter (DOM) on Mn toxicity was characterized in a nutrient‐solution experiment. Manganese toxicity was clearly diminished by silicic acid application, but not by DOM. The former effect probably explains the tolerance of bean plants in peat substrates where high silicon concentrations in the substrate solution were observed. Peat‐clay blends even provided up to five times more silicon to plants than pure peat.

Ericaceae stabilize peat and foster Sphagnum majus establishment at pool margins in restored peatlands

Pools are recognized as biodiversity hotspots in natural peatlands, thus creating pools would increase the ecological value of restored peatlands. However, the peaty margins of artificial pools are unstable, as frost heave creates much surface erosion restricting establishment of vascular plant seedlings. This study evaluates the ability of heather shrubs (Ericaceae) to stabilize created pool margins in restored peatlands. Andromeda polifolia var. latifolia and Vaccinium macrocarpon plants were introduced to form a sparse cover (<25%) at pool margins. Sphagnum majus fragments were spread simultaneously between the shrubs over half the surface at a density of 50% in ground cover, and seeds of herbaceous plants typical of pool margins were sown at two distances from the low-water mark (0.5 and 3.5m). We examined the impact of Ericaceae on (1) frost heave intensity, (2) S. majus establishment and (3) herbaceous species establishment. Treatments using ericaceous shrubs or Sphagnum, both alone or in combination, all reduced frost heave by about 50%. After one year, it also increased survival of S. majus (four-fold) on the wettest soil along the banks. However, at a greater distance from the water (2 and 3.5m), the Sphagnum cover was not influenced by the presence of Ericaceae. Establishment and growth of herbaceous plants grown from seeds were not influenced by the presence of Ericaceae. This study demonstrates the potential of Ericaceae for stabilizing the peat substrate close to the water line and improving survival of S. majus introduced at the immediate edge of created pools.

Tolerance of peat-grown Scots pine seedlings to waterlogging and drought: Morphological, physiological, and metabolic responses to stress

Depending on the soil preparation method applied and peat characteristics, Scots pine (Pinus sylvestris L.) seedlings planted in prepared spots on forestry-drained peatlands may become more susceptible to extreme weather events such as drought or flooding. Only by studying its coping strategies can we eventually design methodology better suited for Scots pine regeneration on peat soils. In this study, we evaluated the tolerance of two-year-old seedlings to the two extremes of water-associated stress, drought and waterlogging, in unprocessed peat. Over one growing season in controlled conditions, drought distinctly reduced root and shoot growth in addition to photochemical efficiency (Fv/Fm) particularly in previous-year needles, whilst wet stress had little discernible impact. Drought also influenced polyamine metabolism by increasing free putrescine and spermine concentrations especially in current-year needles, whereas no impact was discerned in the wet treatment. Furthermore, reduced root hydraulic conductance (Kr) was observed in drought-stressed root systems. Apparently, waterlogging does not modify Scots pine seedling growth or vitality immediately, but rather in the longer term. However, no fatalities occurred in either of the stress treatments, this despite water availability in the Sphagnum peat reaching its lower (permanent wilting point) and upper (10% soil air content) limits. Maintenance of rather high photochemical efficiency despite severe drought stress would seem to indicate a potential for seedling recovery if water availability in the peat substrate improved.

The Effect of Ethrel Application on Length of the Juvenile Phase of Apple Seedlings

A 10 year study (1998-2007) was conducted to work out a method that would allow shortening of the juvenile phase of apple seedlings in conventional apple breeding programs. The investigation was based on two separate experiments, each conducted first in high plastic tunnel and then in the field. In both experiments in the first two years, the seedlings were grown on their own roots in plastic containers (cylinders) placed in the high plastic tunnels. At the end of the second year (December), shoot tips from the seedlings were collected and grafted onto dwarfing rootstock M.9 (winter grafting). By the end of March, the grafts were planted in plastic containers and placed in the same high plastic tunnel. They were cultivated there until mid - August and then planted out to the selection field. In the first experiment, seedlings belonging to two families, ‘Ligol’ x ‘Delbard Jubile’ and ‘Linda’ x ‘Golden Delicious’ were investigated. In the second experiment, two seedling populations, ‘Free Redstar’ x ‘Melodie” and ‘Free Redstar’ x ‘Coop 38’ were tested as well. In the first experiment, nine experimental treatments were studied. They involved two growing media (peat substrate and mixture of peat substrate with compost soil 1:1), two mineral fertilizers (Osmocote Plus and Azofoska - the Polish manufactured fertilizer) and two bioregulators (Gibrescol 10 MG containing GA3 and Ethrel). In the second experiment, additionally compost soil was included. It was found that Ethrel applied twice on young apple seedlings grown in high plastic tunnel, in the first and second year of cultivation in both experiments, shortened the juvenile stage of seedlings grafted and grown on M.9 rootstock. In the first year after planting in the selection field (fourth year after seed germination), 25% of the seedlings produced flowers, and in the second year all of them flowered and produced fruits.

Photosensitised heterogeneous oxidation kinetics of biomass burning aerosol surrogates by ozone using an irradiated rectangular channel flow reactor

Abstract. Heterogeneous reaction kinetics involving organic aerosol and atmospheric oxidants such as ozone can be enhanced under visible or UV irradiation in the presence of a photosensitiser, with subsequent implications for the climate, cloud radiative properties, air quality, and source appointment. In this study we report the steady-state reactive uptake coefficient, γ, of O3 by levoglucosan and 5-nitroguaiacol acting as surrogates for biomass burning aerosol particles, with and without the presence of Pahokee peat acting as a photosensitiser. The reactive uptake has been determined in the dark and as a function of visible and UV-A irradiation and ozone concentration. In addition, γ was determined for 1 : 1, 1 : 10, and 1 : 100 by mass mixtures of Pahokee peat and 5-nitroguaiacol, and for a 10 : 1 : 3 mixture of levoglucosan, Pahokee peat, and 5-nitroguaiacol. We developed a novel irradiated rectangular channel flow reactor (I-RCFR) that was operated under low pressures of about 2–4 hPa, and allowed for uniform irradiation of the organic substrates. The I-RCFR was coupled to a chemical ionisation mass spectrometer and has been successfully validated by measuring the kinetics between various organic species and oxidants. γ of O3 and levoglucosan in the dark and under visible and UV-A irradiation was determined to be in the range of (2–11) × 10−6 and did not change in the presence of Pahokee peat. The determined γ of O3 and 5-nitroguaiacol in the dark was 5.7 × 10−6 and was only enhanced under UV-A irradiation, yielding a value of 3.6 × 10−5. γ of the 1 : 1 Pahokee peat/5-nitroguaiacol substrate was enhanced under visible and UV-A irradiation to 2.4 × 10−5 and 2.8 × 10−5, respectively. Decreasing the amount of Pahokee peat in the 5-nitroguaiacol/Pahokee peat substrate resulted in lower values of γ under visible irradiation, however, γ was consistent under UV-A irradiation regardless of the amount of Pahokee peat. The 10 : 1 : 3 mixture by mass of levoglucosan, Pahokee peat, and 5-nitroguaiacol, under both visible and UV-A irradiation yielded γ values of 2.8 × 10−5 and 1.4 × 10−5, respectively. γ was determined as a function of photon flux for O3 with the 1 : 1 Pahokee peat/5-nitroguaiacol substrate, yielding a linear relationship under both visible and UV-A irradiation. γ of O3 with the 1 : 1 Pahokee peat/5-nitroguaiacol substrate was determined as a function of ozone concentration and exhibited an inverse dependence of γ on ozone concentration, commonly interpreted as a Langmuir–Hinshelwood mechanism. The reactive uptake data have been represented by a Langmuir-type isotherm. From the O3 uptake data under visible irradiation, the following fit parameters have been derived: ks = (5.5 ± 2.7) × 10−19 cm2 s−1 molecule−1 and KO3 = (2.3 ± 2.0) × 10−12 cm3 molecule−1; and under UV-A irradiation: ks = (8.1 ± 2.0) × 10−19 cm2 s−1 molecule−1 and KO3 = (1.7 ± 0.7) × 10−12 cm3 molecule−1. The oxidative power, or the product of γ and [O3], was determined for O3 with the 1 : 1 Pahokee peat/5-nitroguaiacol substrate and was in the range of (1.2–26) × 106 molecule cm−3. Atmospheric particle lifetimes were estimated for a 0.4 μm 5-nitroguaiacol particle as a function of visible and UV-A irradiation and ozone concentration.

First Report of Crown Rot of Strawberry Caused by Macrophomina phaseolina in Chile.

In recent years, an increase of collapsed and dead strawberry plants has been observed in several fields in central Chile, specifically in San Pedro, Melipilla, an important area for strawberry cultivation in the country. To determine the causal agent of the disease and the extent of the problem, 25 sample sites of 1 ha each, distributed in different San Pedro zones, were surveyed at the end of the 2011 season (from December 2010 to February 2011). Cross sections of the crowns of symptomatic strawberry plants showed necrotic tissue and brown-red to dark brown areas on the vascular ring. Samples of the affected crowns were superficially disinfested and plated on potato dextrose agar with 200 μg/ml of streptomycin sulfate. Dark gray colonies were observed after 7 days of incubation at 24°C. Pure cultures of the pathogen showed aerial mycelium and abundant dark oblong sclerotia. Fifty sclerotia were measured, averaging 120 × 74 μm. Twenty-one isolates were identified molecularly utilizing the species specific primers MpKFI and MpKRI (2) that yielded a 350-bp fragment. The amplified DNA fragments were sequenced and BLAST analysis showed a 99% nucleotide sequence identity with Macrophomina phaseolina (GeneBank Accession No JX535007.1). Both morphological and molecular analyses confirmed that the isolated species corresponded to M. phaseolina, causal agent of crown and root rot in strawberry. Four representative isolates were selected to conduct pathogenicity tests. Inoculum was prepared by incubating the pathogen for 28 days at 20°C in sterilized oat seeds. Pots of 1.5 liters were filled with a mixed substrate of peat and perlite (2:1), amended with inoculated oats at 9 g per liter of substrate. 'Camarosa' strawberry plants were planted and grown in a glasshouse for 1 month. Six replicated plants per isolate and six plants growing on non-inoculated substrate were left as controls. Ninety-five percent of the inoculated plants showed wilt and collapse symptoms 22 days after transplant, whereas no symptoms were observed in the control plants. M. phaseolina was reisolated from the crowns of symptomatic plants, fulfilling Koch's postulates. The pathogen was isolated from symptomatic strawberry plants in 14 of the 25 sampled sites. Although M. phaseolina was described previously on other crops in Chile, to our knowledge, this is the first report of M. phaseolina causing crown rot of strawberry. The disease has been recently reported in Spain, the United States, and Argentina (1,3,4).

Substrate influences the height of one- and two-year-old seedlings of silver fir and European beech growing in polystyrene containers

Abstract The effectiveness of different peat-based substrates was compared for the propagation of two mountain tree species (silver fir and European beech). The experiment was set up in the spring of 2006, and seedlings were grown in polystyrene multipots for 2 years. Four types of substrate were applied: (1) a newly prepared 1:1 peat-sawdust mixture; (2) a peat-sawdust mixture which had already been used for five production periods; (3) a peat substrate produced in the ‘Nędza’ container nursery (Rudy Raciborskie Forest District), consisting of peat and perlite; (4) a peat substrate, as described for (3), with added mycorrhizal fungus Hebeloma crustuliniforme. After sowing, polystyrene multi-pots were placed in a transparent tent. During the autumns of 2006 and 2007, for both species and each substrate type, 25 seedlings were randomly selected for measurement of their above-ground height, root length, root collar diameter, above- and below-ground fresh weight. Growth of one-year old and two-year-old seedlings of both species differed depending on their substrate. The application of a mycorrhizal inoculum positively affected seedling establishment, since the best height growth and largest seedlings of both species were grown on substrate (4). The growth of one-year-old fir seedlings in the ‘old’ peat and sawdust mixture (2) was similar to those seedlings grown on the turf substrate (3). Root:shoot allocation differed among the substrates. In fir, root:shoot allocation was approximately equivalent at 1:0.9, whereas for beech it was 1:2 in one-year old seedlings and 1:1.5 in two-year old seedlings.

Endophytic Burkholderia fungorum DBT1 can improve phytoremediation efficiency of polycyclic aromatic hydrocarbons

Burkholderia fungorum DBT1 is a bacterial strain isolated from an oil refinery discharge and capable of transforming dibenzothiophene, phenanthrene, naphthalene, and fluorene. In order to evaluate the influence of a policyclic aromatic hydrocarbon (PAH)-transforming bacterial strain on the phytoremediation of organic contaminants, B. fungorum DBT1 was inoculated into hybrid poplar (Populus deltoides×Populus nigra). The poplar plants were grown for 18-wk with or without naphthalene, phenanthrene, fluorene and dibenzothiophene (488mgkg−1 soil each) in non-sterile sand–peat substrate. Evidences were gained that B. fungorum DBT1 was present in high concentration in poplar root tissues (2.9–9.5×103CFUg−1), while the strain was not detected in stem, leaves and rhizosphere. When poplar was planted in uncontaminated substrate, the infection caused negative effects on biomass index, leaves and stem dry weight, without showing however any disease symptoms. On the other hand, plants inoculated with the strain DBT1 resulted in better tolerance against the toxic effects of PAHs, in terms of root dry weight. Although the presence of plants acted as the main effective treatment for PAH dissipation (82–87%), the inoculum with DBT1 strain lead to the highest PAH abatement (up to 99%). In the present study, an environmental isolate with proper metabolic features was demonstrated to be possibly suitable as a poplar endophyte for improving microbe-assisted phytoremediation in PAH contaminated matrices.

The effect of clay amendment on substrate properties and growth of woody plants

This work deals with the effect of two clay products differing in particle size distribution on properties of growing substrate and on growth of containerized woody plants in substrates amended with these clay products. Fine and coarse clay were added to a peat substrate, each at two rates. The peat substrate without clay was used as a control. The substrates were tested in experiments with two woody ornamentals (Thuja occidentalis’Smaragd’andPrunus cistena). Chemical and physical properties of the substrates were measured according to European Standards before planting. Proportion of water categories differing in availability to the plants were calculated from retention curves measured on the sand box. Properties of substrates in containers with and without plants were evaluated in the same way at the end of the culture. Clay addition changed chemical and physical properties of the tested substrates in terms: available nutrients content, particle density, bulk density, total pore volume, easy available water, water buffering capacity, air capacity, and shrinkage. The effect of fine clay was much stronger. In comparison with the clear effect of clay addition on the substrate chemical and physical properties, the effect on the growth and quality of model woody plants was not so explicit.

Growth and development of captiveGeocrinia rosea(Myobatrachidae): A rare species analogue

Using Geocrinia rosea as an analogue of the two threatened frog species, G. alba and G. vitellina, techniques were developed which contribute to an ex situ rearing program. We tested the effect of two levels of enclosure complexity on metamorph growth, and tested the effect of different substrate types on the success of egg clutch hatching and the subsequent development and growth of metamorph frogs. We found that the simplest enclosure was associated with the highest growth rates and better bone density of metamorphs, while a low pH sphagnum peat substrate was the better substrate for egg clutch survival and subsequent growth of metamorphs. Success of the program was highlighted by the rearing of second-generation frogs. These recommendations have now been applied to the captive management of the two endangered Geocrinia species.

First Report of Damping-off Caused by Pythium aphanidermatum on Leaf Beet (Beta vulgaris subsp. vulgaris) in Italy.

During July 2010, symptoms of crown and root rot were observed on leaf beet (Beta vulgaris L. subsp. vulgaris) grown in a commercial field near Torino (northern Italy). The first symptoms developed 25 days after sowing with temperatures ranging from 25 to 30°C, and 20% of plants were affected. Affected plants were stunted and leaves showed chlorosis and suddenly wilted. The collar and young stems were affected first and appeared brown, water-soaked, and were characterized by a soft rot. Eventually, all affected plants collapsed. Thin aerial mycelia were visible on the surface of the infected plants if maintained at a high relative humidity. Tissue fragments of 1 mm2 were excised from the margins of the lesions, dipped in a solution containing 1% sodium hypochlorite, and plated on potato dextrose agar (PDA) and on a medium selective for oomycetes (2). Plates were incubated under constant fluorescent light at 22 ± 1°C for 5 days. Five isolates, grown on V8 medium (vegetable mix 300 g; agar 15 g; CaCO3 1.5 g; distilled water 1 liter) and observed under light microscope showed the morphological characters of Pythium aphanidermatum (3). This result was confirmed by PCR and sequence analysis. The internal transcribed spacer (ITS) region of rDNA of a single isolate (Py 7/10) was amplified using the primers ITS1/ITS4 and sequenced. BLAST analysis (1) of the 815 bp segment showed a 99% homology with the sequence of P. aphanidermatum (GenBank Accession JN695786). The nucleotide sequence has been assigned to the GenBank Accession JX462954. Pathogenicity tests were performed twice on B. vulgaris subsp. vulgaris grown in 2-liter pots, containing a steam disinfested organic peat substrate (70% black peat, 30% white peat, pH 5.5 to 6, N 110 to 190 mg L-1, P2O5 140 to 230 mg L-1, K2O 170 to 280 mg L-1), infested with wheat and hemp kernels colonized with a strain of P. aphanidermatum at a rate of 1 g L-1. Ten seeds per pot were sown in four pots filled with the infested medium, while the same number of seeds were sown in non-infested substrate. Plants were kept in two growth chambers, at 20 and 27°C. The first symptoms developed 7 days after the artificial inoculation. After 20 days, 70% of plants were infected at 27°C, while 10% were affected at 20°C. Control plants remained healthy at both temperatures. P. aphanidermatum was consistently reisolated from the lesions. To our knowledge, this is the first report of damping off of B. vulgaris subsp. vulgaris caused by P. aphanidermatum in Italy. The importance of the disease, at present limited, could increase in areas where leaf beet is intensively grown.

Effectiveness of selected strains of entomopathogenic nematodes in peat substrate in container breeding

Pest control in urban green areas is particularly difficult due to the limitation of pesticide use. Using efficient methods for biological control of herbivores there may be a good solution. Planting plants growing in the forest container breeding have a better growth and better root system comparing to the seedlings produced in traditional forest nurseries. Such plants are not subject to significant shock when replanted, however, they are still exposed to pests living near plantings. Our research assessed using entomopathogenic nematodes to be introduced into the soil used for plantings in order early protect seedlings against their pests. Nematodes isolated from the natural environment as well as, for control samples, from biopreparations were used in the study. The research was conducted on the soil substrate in containers with seedlings. During the experiment were taken the following parameters: insect mortality, nematode invasion extensity, migration time of invasive larvae, number of migrating larvae, and their survival. The results showed that entomopathogenic nematodes isolated from various provinces in Poland were effective, but characterized by a diverse insecticidal activity in a peat substrate.

Effects of various kinds of potassium fertilizers on the yield and quality of greenhouse tomatoes

The effects of KCl, K&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt; and KNO~ on the yields of greenhouse tomatoes variety 'Revermun' cultivated on a peat substrate were examined. On the basis of fruit yield, dry weight content in the fruit and the content of K, Ca, Mg, Cl, S-SO&lt;sub&gt;4&lt;/sub&gt; in the soil and of N, P, K, Ca, Mg, Cl, S-SO&lt;sub&gt;4&lt;/sub&gt;, Fe, Cu, Mn, Zn, Mo in leaf stalks it was found that KCl is the best form foir fertilizing greenhouse tomatoes cultivated on peat. No adverse effects of chlorine at concentrations of 1500 mg Cl/liter peat and 6,0% Cl in the dry mass of tomato leaves were observed.

Controls on bacterial and archaeal community structure and greenhouse gas production in natural, mined, and restored Canadian peatlands

Northern peatlands are important global C reservoirs, largely because of their slow rates of microbial C mineralization. Particularly in sites that are heavily influenced by anthropogenic disturbances, there is scant information about microbial ecology and whether or not microbial community structure influences greenhouse gas production. This work characterized communities of bacteria and archaea using terminal restriction fragment length polymorphism (T-RFLP) and sequence analysis of 16S rRNA and functional genes across eight natural, mined, or restored peatlands in two locations in eastern Canada. Correlations were explored among chemical properties of peat, bacterial and archaeal community structure, and carbon dioxide (CO2) and methane (CH4) production rates under oxic and anoxic conditions. Bacteria and archaea similar to those found in other peat soil environments were detected. In contrast to other reports, methanogen diversity was low in our study, with only 2 groups of known or suspected methanogens. Although mining and restoration affected substrate availability and microbial activity, these land-uses did not consistently affect bacterial or archaeal community composition. In fact, larger differences were observed between the two locations and between oxic and anoxic peat samples than between natural, mined, and restored sites, with anoxic samples characterized by less detectable bacterial diversity and stronger dominance by members of the phylum Acidobacteria. There were also no apparent strong linkages between prokaryote community structure and CH4 or CO2 production, suggesting that different organisms exhibit functional redundancy and/or that the same taxa function at very different rates when exposed to different peat substrates. In contrast to other earlier work focusing on fungal communities across similar mined and restored peatlands, bacterial and archaeal communities appeared to be more resistant or resilient to peat substrate changes brought about by these land uses.

Nitrification in Pine Tree Substrate Is Influenced by Storage Time and Amendments

Pine tree substrate (PTS), for container plant production, is a relatively new alternative to the commonly used pine bark and peat substrates. Fertility management requires knowledge of nitrogen transformations in this new substrate. The objective of this study was to document the occurrence of nitrification in PTS and to determine if nitrification and density of nitrifying microorganisms are affected by substrate storage time and lime and peat amendments. Pine tree substrate was manufactured by hammermilling chips of ≈15-year-old loblolly pine trees (Pinus taeda L.) through two screen sizes, 4.76 mm (PTS) and 15.9 mm amended with peat (3PTS:1 peat, v:v, PTSP). Pine tree substrate and PTSP were amended with lime at five rates and a peat–perlite mix (4 peat:1 perlite, v:v, PL) served as a control treatment for a total of 11 treatments. Substrates were prepared, placed in plastic storage bags, and stored on shelves in an open shed in Blacksburg, VA. Subsamples were taken at 1, 42, 84, 168, 270, and 365 days after storage. At each subsampling day, each substrate was placed into 12 1-L containers. Six of the 12 were left fallow and six were planted with 14-day-old marigold (Tagetes erecta L. ‘Inca Gold’) seedlings; all containers were placed on a greenhouse bench. Substrates were also collected for most probable number (MPN) assays for nitrifying microorganism quantification. Substrate solution pH, electrical conductivity (EC), ammonium-N (NH4-N), and nitrate-N (NO3-N) were measured on fallow treatments. Marigold substrate solution pH, EC, NH4-N, and NO3-N were measured after 3 weeks of marigold growth. Nitrate-N was detected in fallow containers at low concentrations (0.4 to 5.4 mg·L−1) in PTS in all limed treatments at all subsampling days, but in the non-limed treatment, only at Days 270 and 365. Nitrate-N was detected in the fallow containers at low concentrations (0.7 to 13.7 mg·L−1) in PTSP in the 4- and 6-kg·m−3 lime rates at all subsampling days. Nitrite-oxidizing microorganisms were present in PTS at all subsampling days with the highest numbers measured at Day 1. Ammonium-to-nitrate ratios for the marigold substrate solution extracts for both PTS and PTSP decreased as pH increased. This study shows that nitrifying microorganisms are present and nitrification occurs in PTS and PTSP and is positively correlated to substrate pH.

Micropropagation of Vaccinium arctostaphylos L. via lateral-bud culture

The aim of this study was to determine the most suitable growth medium for rapid and efficient micropropagation of Vaccinium arctostaphylos L. (Ericaceae) via lateral-bud cultures. According to preliminary studies, the best explant collection time was late April and May. Accordingly, cuttings were taken from naturally growing V. arctostaphylos populations, and lateral shoot buds were used as explant sources. Anderson's rhododendron medium (AN), McCown's woody plant medium (WPM), and Murashige and Skoog (MS) basal medium, each supplemented with zeatin/indole-3-butyric acid (IBA) (1.0/0.1 mg L^{-1}), were tested to determine the best basal medium for multiple shoot formation; WPM was the most effective basal medium for this purpose. Subsequent shoot multiplication and development studies were carried out with WPM supplemented with an auxin, IBA (0.1 mg L^{-1}), and 2 different cytokinins, zeatin and thidiazuron (TDZ), in various concentrations (0.5, 1.0, and 2.0 mg L^{-1}, respectively). After a 6-week photoperiod (16/8 h, light/ dark) application, zeatin/IBA combinations were found to be the most suitable for shoot multiplication and growth. The highest shoot length (106.53%) was obtained from the medium supplemented with 1.0/0.1 mg L^{-1} zeatin/IBA, while the highest increases in leaf number (141.89%) and multiple shoot proliferation (10.55-fold) were obtained from medium supplemented with 2.0/0.1 mg L^{-1} zeatin/IBA. WPM was also employed as a rooting medium supplemented with different concentrations of IBA (from 0.5 mg L-1 to 8.0 mg L-1) and a 16/8 photoperiod or a completely dark regime. At this stage, the medium supplemented with 0.5 mg L^{-1} IBA was the best rooting growth regulator with 100% rooting success (16/8 photoperiod). Rooted plantlets transplanted into peat and perlite (2:1) substrate were subsequently acclimatized under climate chamber conditions.