Peat Culture Research Articles

Metabolomics and network pharmacology profiling revealed soilless cultivation reduces the accumulation of harmful compounds in Houttuynia cordata

Houttuynia cordata Thunb (HCT), an important homologous plant, has extensive medicinal and food value. Traditional Chinese medicine may have therapeutic research value for inhibiting COVID-19 toxicity. HeadSpace Solid Phase Micro-Extraction Gas-Chromatography-Mass-Spectrometry (HS-SPME-GC–MS) was used in this study to examine the edible quality, differences in growth indicators, and metabolite differences of HCT under different cultivation media (soil, sand, peat, hydroponics). Additionally, network pharmacology was used to study the active substances and key targets of Houttuynia cordata against COVID-19. The experimental analysis indicated that hydroponics produced the highest HCT yield and that the soil culture produced the highest growth parameters such as dry rate, chlorophyll content, and vitamin C content. The sand culture produced the highest total protein content, and the peat culture resulted in the highest accumulation of total flavonoids. However, compared with the soilless culture, the soil culture's environment produced more benzene and substituted derivatives and more carboxylic acids and derivatives. Hydroponics reduces the accumulation of harmful metabolites and enhances the accumulation of medicinal components in HCT. In summation, HCT is suitable for soilless cultivation and shows demonstrates strong performance in medicinal quality and growing development under hydroponics.

Role of Benzoic Acid and Lettucenin A in the Defense Response of Lettuce against Soil-Borne Pathogens.

Soil-borne pathogens can severely limit plant productivity. Induced defense responses are plant strategies to counteract pathogen-related damage and yield loss. In this study, we hypothesized that benzoic acid and lettucenin A are involved as defense compounds against Rhizoctonia solani and Olpidium virulentus in lettuce. To address this hypothesis, we conducted growth chamber experiments using hydroponics, peat culture substrate and soil culture in pots and minirhizotrons. Benzoic acid was identified as root exudate released from lettuce plants upon pathogen infection, with pre-accumulation of benzoic acid esters in the root tissue. The amounts were sufficient to inhibit hyphal growth of R. solani in vitro (30%), to mitigate growth retardation (51%) and damage of fine roots (130%) in lettuce plants caused by R. solani, but were not able to overcome plant growth suppression induced by Olpidium infection. Additionally, lettucenin A was identified as major phytoalexin, with local accumulation in affected plant tissues upon infection with pathogens or chemical elicitation (CuSO4) and detected in trace amounts in root exudates. The results suggest a two-stage defense mechanism with pathogen-induced benzoic acid exudation initially located in the rhizosphere followed by accumulation of lettucenin A locally restricted to affected root and leaf tissues.

Preliminary investigation on the potential use of two C4 turfgrass species to reduce nutrient release in a Mediterranean drained peatland.

This study compared dry matter production, nutrient uptake and tissue nutrient concentration of two C4 turfgrass species (Cynodon dactylon × Cynodon transvaalensis Burtt Davy and Paspalum vaginatum Swartz) supplied with three different nutrient solutions in a sand and peat culture. The 8-week experiment was performed in mesocosms and simulated the conditions of an open-field phyto-treatment system located in a Mediterranean drained peatland (Tuscany, Italy). Peat was collected on the site, and one of the solutions mimicked drainage water flowing into it. Three hypotheses were tested: (i) the species chosen efficiently removed nutrients from both the solution and the substrate; (ii) peat contributed to the nutrient load; and (iii) the species chosen were suitable in the open-field system. Both species adapted well to the experimental conditions and demonstrated considerable ability to remove nutrients. P. vaginatum took up nitrogen more efficiently, mainly in conditions of high nutrient availability. We observed supplementary nutrient uptake by plants in the peat treatment. Performances of the two C4 turfgrasses extrapolated to the field scale seemed effective from a phyto-treatment perspective.

Application of chlorophyll fluorescence for the diagnosis of salt stress in tomato “ Solanum lycopersicum (variety Rio Grande)”

To study the response of tomato ( Solanum lycopersicum cv. Rio Grande) to salinity, the effect on plant growth, water relations, stomatal conductance and Chlorophyll fluorescence was investigated. Tomato plants were grown in peat culture under controlled conditions and submitted during 28 days to saline stress ranging from 0 to 25, 50, 100, 150 and 200 mM of NaCl. At the end of the experiment period, plant growth was significantly decreased with increasing salinity. During the three weeks following the application of NaCl, stomatal conductance ( g s) and water potential ( ψ w) decreased gradually with the increase of salinity. Indeed, salinity treatment showed no changes in all chlorophyll fluorescence parameters. In the fourth week, the water potential and stomatal conductance decreased significantly. PSII photochemistry in light-adapted leaves was modified in salinity-stressed plants; while in dark-adapted leaves, there were no changes in the maximum quantum efficiency of the PSII photochemistry. The strong correlations between the foliar content of Na + and Chl a fluorescence characteristics (the actual PSII efficiency ( Φ PSII), the photochemical quenching ( q p), the non photochemical quenching (NPQ), and the linear electron transport rate (ETR)) suggest that these parameters can be used to screen genotypes for salt tolerance.

Morphological changes of rhizobia in peat cultures.

Morphological changes that take place in peat cultures of several species of rhizobia were examined. These changes seemed to be associated with enhanced survival of cells in peat and after inoculation onto plastic beads, which were used as a model system for seeds. Cell wall changes, in which the periplasmic space appeared to be occluded with electron-dense material, were observed in Rhizobium sp. strain SU343 and Bradyrhizobium lupini WU425 cells after 7 and 14 days in peat, respectively. Nutrient limitation and low O(2) concentration in peat are suggested to be factors involved in the induction of the morphological changes. Polyhydroxybutyrate reserves, which were present in broth-cultured cells of both species of rhizobia, were mobilized after transfer into peat but did not appear to influence survival after inoculation onto beads. Enhanced expression of an iron-manganese superoxide dismutase was also observed after the cells were transferred into peat. We conclude that cell wall thickening in rhizobia after transfer from broth cultures into peat is an adaptive response for long-term survival under nutrient-limited conditions in peat. Cells with thickened walls may also be more resistant to other types of stress, such as that encountered on a seed surface.

Growth and survival of root-nodule bacteria in legume inoculants stored at high temperatures

The maximum temperatures to which legume inoculants were exposed when despatched to five destinations in Australia (36–39°C) and nine in Indonesia (29–42°C) were used to define experimental storage conditions to study survival of root-nodule bacteria in peat culture. Cultures of three strains of Bradyrhizobium and two strains of Rhizobium were prepared in sterilised peat at a moisture potential of −log 10 4.5 Pa and incubated at 25°C for 14 days. They were then stored at either 25, 30, 35 or 40°C for 28 days. There was no significant effect of temperature in the first 5 days. By day 7, the numbers of the clover strain declined significantly at temperatures between 30 and 40°C and those of the medic, lupin and both soybean strains at 40°C. Numbers of all strains exceeded log 10 8.3 g −1 peat when stored at 35°C for 28 days; the two strains for soybeans exceeded log 10 9.0 g −1. Although when stored at 40°C for 2 weeks, the numbers of the five strains declined, they all multiplied rapidly when returned to 25°C. This response was repeated when the same packets were subjected to this regimen a second time. After a third cycle, recovery when returned to 25°C was slower than before but numbers still exceeded log 10 7.6 g −1 peat. Storage at 40°C for 42 days did not affect the infectivity of the strains. These results indicate that peat-based cultures may be distributed with safety in the tropics from a centralised production centre. Regional reincubation at a favourable temperature (25°C) for growth is recommended when temperatures inside the packaging are likely to have exceeded 35°C for 7 days.

Field persistence of Bradyrhizobium sp. (Lupinus) inoculant for serradella (Ornithopus compressus L.)

Experiments were conducted, in situ in north-western New South Wales and in the laboratory, to evaluate the longevity of Bradyrhizobium sp. (Lupinus) inoculated as a peat culture onto seed of yellow serradella (Ornithopus compressus L.). Observations were made on the field persistence of the inoculant strain over 2 years. Two categories of seed were examined: seed encased in a segment of pod coat (hulled), and seed from which the pod coat had been removed (dehulled). The use of adhesive (methyl cellulose or gum arabic) ensured that the inoculant adhered to the seed. At a constant temperature of l8�C, inoculant applied to hulled seed survived for >8 months without loss of viability. Type of adhesive did not affect survival. At the 2 field sites, inoculated seed was sown into dry soil. Inoculant was sufficiently viable for 77-159 days to colonise the rhizospheres of young serradella and to form nodules on a significant (P<0.05) proportion of the plants. Rhizosphere colonisation and nodulation were better with hulled seed than with dehulled seed but were not affected by type of adhesive. Evidence is presented that the inoculant was able to establish in these soils as a permanent component of the soil microflora and to persist as a reservoir of inoculum for annually regenerating serradella.

Validation of a serial-dilution, plant-infection test for enumerating Rhizobium leguminosarum bv. viciae and its application for counting rhizobia in acid soils

Rhizobium leguminosarum bv. viciae resident in soil cannot be distinguished from other root-nodule bacteria by cultural means so indirect methods of identification and enumeration are used in ecological studies. A dilution-nodulation frequency technique (plant-infection test) is described whereby Vicia hirsuta, a small-seeded species related symbiotically to pea, lentil, faba bean, other vetch and chickling, is grown in test tubes plugged with flexible polyurethane foam for counting R. leguminosarum bv. viciae. This plant-infection test was compared with counting of pure cultures in broth and peat on agar spread-plates. Comparisons were also made between counts of pure cultures in broth and plant-infection counts of soil-rhizobia mixtures prepared from those cultures. Provided that the V. hirsuta test plants were grown in vermiculite, not agar, both the plant-infection test and plate counting gave similar results with broth culture. With peat culture and soil-rhizobia mixtures, the estimates of rhizobial numbers obtained with plant-infection tests were usually higher than those obtained with spread-plates; in about 23% of instances the differences, although small bacteriologically, were significant ( P < 0.05). The discrepancy may be attributable to more efficient dispersion of clumps of cells resulting from the operations used in preparation of serial dilutions for the plant-infection tests. In all other respects the data showed that the plant-infection test, utilizing V. hirsuta as a test plant, was an appropriate and valuable technique for enumeration of R. leguminosarum bv. viciae in the field. The plant-infection test was used in a survey of populations of R. leguminosarum bv. viciae resident in 62 acid soils in New South Wales where inoculated field peas had grown just once. The populations were generally small (geometric mean 23 g −1 soil) and, in 19 soils, undetectable. There was a significant correlation ( P < 0.001) between population size and degree of soil acidity but no relationship between population and time since growth of peas. It is concluded that the number of R. leguminosarum bv. viciae surviving in soil after a pea crop depends on the degree of acidity, not on how recently the crop was grown.

Fungal Keratitis After Radial Keratotomy

Inquiries to Eduardo Alfonso, M.D., Bascom Palmer Eye Institute, P.O. Box 016880, Miami, FL 33101. A 35-year-old woman had a history of Crohn's disease that was treated with sulfasalazine. The patient had six-incisional radial kera­ totomy of both eyes; the right eye in October 1990, and the left eye in January 1991. Postoperatively the right eye had done well. However, two weeks postoperatively, the left eye became red and irritated while on a regimen of antibiot­ ic and corticosteroid drops. The surgeon noted an infiltrate in the central aspect of the 5 o'clock incision. The patient was treated with topical fortified cefazolin, fortified tobramycin, and dexamethasone without improvement. Cul­ tures yielded no growth. On March 6, 1991, the patient was referred to a corneal specialist be­ cause of continued irritation and pain. A diag­ nosis of crystalline keratopathy was made. The wound at the 5 o'clock incision was irrigated with vancomycin (50 mg/ml) . Vancomycin (50 mg) and gentamicin (40 mg) were injected subconjunctivally, and the patient was given topi­ cal fortified cefazolin, fortified tobramycin, Neosporin, and fluorometholone 0.25%. Re­ peat cultures yielded no growth. On March 18,

The effect of moisture potential on growth and survival of root nodule bacteria in peat culture and on seed

Peat from three sources was dried, milled and packed separately in polyethylene bags and sterilized by irradiation. The carrier was impregnated with broth cultures of either Rhizobium leguminosarum bv. trifolii strain WU95, Bradyrhizobium japonicum strain CB1809 or B. lupini strain WU425 and sterile water to provide five moisture potentials in the range > - 1 × 104 - 1 × 106 Pa. The packets were stored at 26°C under conditions which restricted moisture loss. Numbers of root nodule bacteria were counted at intervals up to 12 weeks. No single moisture potential was optimum for all strains in all carriers because of a significant (P < 0.05) interaction between moisture potential × strain × carrier × time. Where direct comparisons could be made, all strains survived best at - 1 × 104 and/or −3.2 × 104 Pa. Seeds of Trifolium subterraneum and polypropylene beads (used to avoid seed coat toxicity), were inoculated with WU95 prepared in two sources of peat and at each of the above moisture potentials and stored at 15°C. Seed coat toxicity significantly effected the log death rate (k) of WU95 on subterraneum clover seed for the period 0–0.25 d (k1.796) compared with k - 0.399 for polypropylene beads. In the first 24 h moisture did not affect survival but by 28 d rhizobia grown in Badenoch peat survived best at −3.2 × 104 Pa. In Millicent peat, survival was equally as good at −3.2 × 104 and −1 × 104 Pa.

The effect of packaging films on growth and survival of rhizobia in peat culture

The growth and survival of two strains of rhizobia (Rhizobium leguminosarum bv. trifolii strain WU95 and R. spp. strain CB3060) injected into finely milled, sterile peat contained in packets of various packaging films were compared after 2, 4 and 8 weeks storage at 26°C. The films were 50 μm and 100 μm low density polyethylene (LDPE), 50 μm high density polyethylene (HDPE) and polyethylene laminated foil and were chosen to provide a range of gas transmission and water permeability properties. Survival of both strains varied directly with the transmission and permeability properties of the film, under controlled storage conditions. These findings provide further evidence that a degree of aeration is necessary for survival of rhizobia in peat‐based legume inoculants. The choice of the most suitable film needs consideration of the moisture characteristic curve of the carrier.

The role of bacteria in pH increase of nettle water

The investigation was designed to elucidate and explain the pH increase observed when a water extract of stinging nettle,Urtica dioica, was supplied to plants grown in sand or peat culture. The pH, bacterial number, organic acid content, and NH4+ and NO3− content were determined in aerated nettle water, sterilised (UV-treated) nettle water and nutrient solution at intervals during 48 h. The pH increase was closely linked to increase in aerobic bacteria and the simultaneous decrease in organic acids and NH4+ concentration in the media. Consequently, the pH rise in nettle water is due to consumption of organic acids by bacteria and the accompanying shift of the acid-base equilibrium towards a more basic state.

Differential tolerances of weed species to aluminum, manganese and salinity

Abstract Seven weed species were screened for tolerance to acid soil factors (Al and Mn toxicities) and to saline soil factors (NaCl and Na2SO4) in greenhouse peat cultures. Species used were: Echinochloa crusgalli (L.) Beauv. var. crusgalli‐barnyard grass; Kochia scoparia (L.) Schrad.‐Kochia‐summer cypress; Setaria viridis (L.) Beauv.‐green foxtail; Amaranthus retroflexus (L.) ‐ redroot pigweed; Chenopodium album (L.) ‐lambsquarters; Convolvulus arvensis (L.) ‐ field bindweed; and Avena fatua (L.) ‐ wild oat. Species showed wide differences in tolerance to both acid and saline soil factors. Kochia scoparia, Setaria viridis, Echinochloa crusgalli and Avena fatua were tolerant or moderately tolerant to both excess Al and Mn. By contrast, Chenopodium album, Amaranthus retroflexus and Convolvulus arvensis were sensitive to Al and Mn. Echinochloa crusgalli was exceptionally tolerant to both NaCl and Na2SO4 salinity, and Chenopodium album and Avena fatua were moderately tolerant to both salinity factors. In contrast, Convolvulus arvensis and Amaranthus retroflexus were sensitive to both to NaCl and Na2SO4. Kochia scoparia appeared more tolerant to Cl‐ than to SO4 2‐ Echinochloa crusgalli and Avena fatua were tolerant to Al and Mn and also to NaCl and Na2SO4 salinity. Convolvulus arvensis and Amaranthus retroflexus were sensitive to both Al and Mn and to NaCl and Na2SO4. These findings may be helpful in weed control or in the use of wild plants for reclamation of saline and acid soils.

A 86Rb BIOASSAY TO DETERMINE THE POTASSIUM STATUS OF TREES

SummaryA bioassay method has been developed to test for potassium deficiency in forest trees; it is based on the metabolic uptake by excised roots of 86Rb from 5 × 10−6 M rubidium chloride solution during a period of 15 min. Betula pubescens Ehrh. seedlings were grown in sand culture supplied with Hewitt's nutrient solution containing K at concentrations between 1 and 200 mg l−1. A negative curvilinear relationship was demonstrated between uptake by the seedlings of 86Rb from the rubidium chloride solution and the concentration of K previously supplied in the growth medium. When roots of intact plants were immersed in 86Rb‐labelled solution for 15 min, less than 1% of 86Rb taken up was translocated to the shoots. A similar response curve, relating 86Rb uptake to K supplied to growing plants, was demonstrated when Picea sitchensis (Bong.) Carr seedlings were grown in peat culture with K added at 0 to 400 mg l−1. In three field trials of the bioassay, roots were excised from P. sitchensis and Pinus contorta Douglas ex Loud, growing on peat or peaty gley plots where different amounts of fertilizer had been added to give a range of degrees of K deficiency or from unfertilized, control plots. The patterns of 86Rb uptake by excised roots indicated that the method is potentially useful for the rapid determination of K deficiency in forest trees.

Population dynamics of Rhizobium japonicum strains used to inoculate three successive crops of soybean

Three closely related strains of Rhizobium japonicum, equally effective in N2 fixation, were used to inoculate each of three successive crops of soybeans [Glycine rnax (L.) Merr. cv. Bragg] grown on the same block of land. The soil was a vertisol previously free of R. japonicum, and inoculant was applied at different rates by spraying a suspension of peat culture into the seed bed at time of sowing the seed. The populations of rhizobia that developed in rhizosphere and soil were counted at intervals during crop growth and in the fallow period between crops. There was usually a substantial decline in recovery of inoculant strains immediately after sowing. In soil initially devoid of R. japonicum, populations in the rhizospheres of young seedlings were related to rates of inoculation, but differences disappeared as the plants aged. Shortly after harvest, the soil contained large populations of rhizobia which increased up to 200 times during the fallow period between crops, probably due to release of bacteria from disintegrating nodules. The size of these populations was maintained up to the time of sowing the following crop. Although strains used for second- and third-year crops were dominated by already established rhizobia in rhizosphere colonization and nodule formation, the magnitude of the domination could be reduced by increased rates of inoculation. In soil already containing R. japonicum, the proportion of nodules formed by inoculant strains was greater than the relative number of inoculant rhizobia in the soil or the rhizosphere; this was ascribed to an advantage of specific placement of the inocula in that zone of the soil where infection foci first formed. The results are explicable in numerical terms and are discussed in relation to an inoculation strategy for maximum nodulation by applied inoculant in competition with rhizobia already established in soil.

The effect of delayed inoculation on nitrogen fixation byPhaseolus vulgarisL. Grown in minesoil

Abstract The influence of delayed inoculation on N2(C2H2)‐fixation by Phaseolus vulgaris L. grown in minesoil is described. Fertilizer treatments included in the study were 0, 25, 50, and 100 kg N/ha applied at 21 days or at seeding. A peat culture of Rhizobium phaseoli was inoculated at 21 days or at seeding. Nitrogenase activity was determined by reduction of C2H2 to C2H4, at 7, 21, 35, and 49 days. Nitrogenase activity was related to N‐fertilizer rate and treatment sequence. Addition of 25 kg N/ha significantly stimulated N2(C2H2)‐ fixation while greater rates of N‐fertilizer decreased the rate of Ng(C2H2)‐fixation. The results of this study suggest that addition of 25 kg N/ha at time of seeding, followed by inoculation with R. phaseoli after legume growth has been established (21 days) results in an initial greater amount of N2(C2H2)‐fixation.

Preliminary experiments into the use of Streptomyces spp. isolated from peat in the biological control of soil and seed-borne diseases in peat culture

Streptomyces spp. isolates obtained from peat effectively inhibited the growth of Alternaria brassicicola Wiltshire, Fusarium culmorum (W. G. Smith) Sacc., F. sulphureum Schlechtendahl, Pythium debaryanum auct. non Hesse and Rhizoctonia solani Kühn on PDA medium, but Streptomyces spp. isolates from fine sand soil were not effective against F. culmorum compared to the strains isolated from peat. Treatment of cauliflower seeds with Streptomyces spp. isolated from peat effectively controlled damping-off caused by A. brassicicola and R. solani when the seedlings were grown on either disinfected or fresh peat. Spraying the seeding layer of the peat substrate with a suspension of Streptomyces reduced the mortality of barley sprouts and foot rot caused by F. culmorum, and damping-off on sugar beet caused by P. debaryanum.

Effects of spray inoculation equipment on the viability of Rhizobium spp. in liquid inoculants for legumes

Pumping equipment designed for seedbed inoculation of legumes with liquid inoculants was set up on a test bed in the laboratory. Experiments, in which liquid inoculant was circulated through the equipment, were conducted to determine the effect on inoculant viability of variables likely to be encountered when farmers used the equipment in the field. Provided that peat cultures of Rhizobium spp. were used to make liquid inoculant, neither pump type, operating pressure up to 173 kPa, water temperature up to 35�C, nor water impurity up to a level equivalent to 170 �S/cm conductivity seriously reduced inoculant populations during the first hour of treatment, although a significant decline in numbers occurred in three out of 16 experiments. When inoculant was exposed to the various treatments for long periods, a significant loss of viability occurred, in 7 out of 13 experiments, between 4-8 h. R. meliloti was least affected by treatment and R. leguminosarum most affected, but this may have been due to strain differences as much as to species differences. Liquid inoculants which were made from broth cultures lost viability very quickly. R.. meliloti liquid inoculant, prepared from a peat culture and introduced by spraying into a dry soil of neutral pH in the absence of any host plant, did not lose viability during a period of four weeks. The spray inoculation equipment was also used successfully in a field experiment to add water to the seedbed to aid in the germination of soybean seed sown into drying soil.

Competitive advantage of bacteriocin and phage-producing strains of Rhizobium trifolii in mixed culture

Bacteriocinogenic and lysogenic strains of Rhizobium trifolii were grown with sensitive strains in sterile broth or peat culture. In broth culture the producing strains strongly suppressed growth of sensitive strains. In peat culture a considerable degree of suppression was also observed, the effect being stronger when the peat was “wet” than when it was “damp”. Apparently, conditions which favour growth in peat also favour dominance by bacteriocinogenic or lysogenic bacteria in cultures of mixed strains. The results are discussed in relation to preparation of mixed-strain legume inoculants and to studies of competition between strains in the field environment.

Survival of Rhizobium trifolii strains on inoculated seed held at 35°C

Fifteen Rhizobium trifolii strains, selected from 62 isolations from naturalized white clover (Trifolium repens) plants on the far north coast of New South Wales, were tested for their tolerance to high temperature. They were compared with TAI (the current commercial strain) and CC275e, when used as peat cultures to inoculate seed held at 35�C. TAI showed the most rapid decline and its death rate was significantly higher than that of all except one of the isolates. CC275e showed good survival, and its death rate was similar to the lowest in two out of the three groups in which it was included. Differences between local isolates were small except for two which showed poorer survival.