Evaluation of the Effective Inactivation of Enteric Bacteria and Viruses From Swine Effluent and Sludge at Tropical Temperatures

The safe recycling of organic wastes such as the nutrients obtained from agriculture activities is a relevant aspect of the “One Health” strategy, a worldwide initiative including all aspects of health care for humans and animals, as well as aspects related to the conservation and development of the environment. It represents an important opportunity to mitigate the potential impact of microbial pathogens likely present in nutrient natural sources, as digestate, when applied to land as fertilizers. The objectives of the current study were to determine the inactivation of enteric microorganisms in swine digestate (effluent and sludge) during storage in anaerobic conditions and at different ambient temperatures of tropical zones (16, 22, and 37 °C). Human adenovirus 2 (HAdV-2), bacteriophage PhiX-174, and Salmonella enterica serovar typhimurium (S. typhimurium) were used as enteric microbial models to determine the minimum storage time required to reduce at least 3log of enteric microorganisms load in both matrices at the mentioned temperatures. The minimum storage time required for S. typhimurium was shorter than those observed for viruses at 37 °C, while reduction of at least 3log for S. typhimurium was observed after just 1 day; 20 and 90 days were needed for similar reductions for HAdV-2 and PhiX-174, respectively. Similar results were also observed at lower temperatures: 30 and 45 days were needed for S. typhimurium at 22 and 16 °C, respectively, but 30 and 90 days were needed at 22 °C for HAdV-2 PhiX-174, respectively, or 90 and 120 days at 16 °C for HAdV-2 PhiX-174, respectively. This is a pioneering study on the evaluation of inactivation of enteric viruses in swine digestate in usual tropical ambient temperatures; it demonstrates that the time for a considerable inactivation is longer than that observed for a enteric microorganisms (S. typhimurium), and shows that the storage of swine digestate at the referred temperatures can be used as a low-cost post-treatment to inactivate enteric microorganisms, allowing a further use as safer fertilizer.     

Effects of acidic meltwater on chemical conditions at nearshore spawning sites

Chemical conditions at lake charr (Salvelinus namaycush) spawning sites were monitored during snowmelt in low alkalinity lakes in Ontario, Canada. Embryos within the interstitial water of the spawning substrate were exposed to abrupt and potentially toxic levels of H⁺ and inorganic Al as acidic runoff water inundated the shallow nearshore sites. Early runoff events, those that occurred while the lake ice was still snow-covered and under-ice water temperatures were <2°C, appeared to be most threatening, because of deep penetration of the runoff water. These highly site-specific events exhibit wide temporal and spatial variability.     

Temperaturansprüche mikroskopischer Bodenpilze aus klimatisch und geographisch verschiedenen Standorten

Temperature demands of microscopic soil fungi from different climatic and geographical sites. . 154 strains of microscopic soil fungi were isolated at 25°C from soils deriving from tropical to alpine climatic zones of the world (SW-Africa, Argentine, Nepal, Canary Islands and W-Germany). Determining their saccharolytic, amylolytic and proteolytic activities on saccharose-, starch- or gelatine-containing agar plates at 5 °C, 15 °C, 25 °C, 35 °C and 43 °C, the activity range as well as the optimal temperature were obtained. The following results were obtained: 1) A clear correlation between the temperature requirements of the fungal flora and the climatic conditions of the site of isolation was observed. 2) The fungal flora of a certain climatic zone was composed of strains of ubiquitously distributed species. Their great adaptability enables them to accomodate themselves to the temperature conditions of each site. 3) A smaller percentage of species was characterised by a small range of temperature variability and therefore depending on a certain climatic zone. Some of these were strict pschychrophilic species, characteristic for alpine and subalpine regions, but others behaved as strict mesophiles observed only in warm regions. 4) Finally from each site of isolation there also could be isolated a certain amount of fungi, whose ecological demands did not or only for a very short time coincide with the bioclimatic conditions of the particular site. Generally, these isolates are able to form resistant spores enabling them to survive unfavourable climatic conditions. .     

Yields nutrient intake and soil fertilizing in 40 years fertilizer trials

The set of twenty long‐term field nutrition trials starting from 1957 at five sites. The sites differed by their altitude (from 180 m to 620 m) with average daily temperatures (from 6,8°C m to 9°C m) and soil type (from chernozem to brown podsolic soil) Provided mainly the following results:

? The geonomic division to the fertile sugarbeet region and less fertile potato region did not strictly differentiate the influence of fertilizer and climatic effects to the crop yields.

? The effect of fertilizing was dependent on the nutrient content and on the conditions of releasing and binding of the nutrients in soil.

? The precipitation regime has a strong influence on the effect of the nitrogen escalated doses.

? The facts concerning the nutrient intake are very precious knowledge. These facts have not been examined yet during the long‐term trials.

? The site effect, particularly its climatic conditions, on the nutrient intake is often more obvious compared to the fertilizing effect.

? Very interesting impulses for further research monitoring during the long‐term trials was contributed by “mapping”; of soil capacity to provide nutrients to plants at various sites and under different climate.     

Effects on Pasting Viscosity of Starch and Flour from Different Operating Conditions for the Rapid Visco Analyser

Three wheat flours, three wheat starches, a regular maize starch and a waxy maize starch were subjected to a number of different RVA profiles. Five different initial temperatures were used, 40, 50, 55, 60, and 65°C, with different initial holding times (0–3 min), heating times (2fl–10 min), holding times at 95°C (0–6 min), cooling times (2–6 min), and final hold times (0–10 min) being applied. A range of final temperatures of 30–60°C was also utilized. Significant variations in viscosity were observed with these conditions, particularly in wheat starch and flour. The most important parameters causing these variations were the initial temperature, the heating rate, and the final holding time. Short initial holding times also resulted in a wider spread of values for peak viscosity although there was little effect on the mean value and no significant effect on the holding strength or final viscosity. The final temperature was also important in that lower temperatures gave more viscous gels. Provided that the desired cooling rate could be achieved, varying the cooling time had no effect on the peak or trough viscosities and only a very minor effect on the final viscosity. If final temperatures of 40°C or lower are to be used, the cooling conditions and final hold time would need to be adjusted so that maximum viscosity could be achieved. A proposal for a standard Rapid Visco Analyser (RVA) procedure is: at least 1 min at 50°C, heat to 95°C over 4 min, hold at 95°C for 4 min, cool to 50°C in 3 min, and hold at 50°C for 4 min. These conditions should minimize variation within samples and should allow a better comparison between samples.     

Soil temperature,mycorrhizal infection and nodulation of Medicago truncatula and Trifolium subterraneum

Establishment of vesicular-arbuscular mycorrhizal fungi in plant roots involves a pre-infection phase of propagule germination, hyphal growth and appressorium formation, followed by growth of the fungus within the root. The effect of soil temperature on the pre-infection stage was examined by counting the numbers of fungal “entry-points” on the main roots of Medicago truncatula and Trifolium subterraneum, grown at soil temperatures of 12°, 16°, 20° and 25°C for periods up to 12 days. Increased root temperature was positively associated with increased numbers of “entry-points”. This effect was more marked between 12° and 16°C than at higher temperatures, as shown by comparing plants at the same stage of development (emergence of spade leaf) and by calculating the results as entry points per cm root.The first root nodules appeared sooner at higher temperatures (20° and 25°), but subsequent development of nodules (measured as nodule number and aggregate volume of nodules per plant, up to 21 days) was best at 16°C for both host Rhizobium combinations in non-sterile and autoclaved soil. There was no evidence that competition between mycorrhizal fungi and Rhizobium for infection sites occurred.A method of obtaining numbers of infective propagules of vesicular-arbuscular mycorrhizal fungi in soil is described.     

A computer simulation model for soil temperatures in Australian cereal cropping

The effect of tillage on soil temperature and the effects of temperature on plant performance have been investigated by various authors, but soil temperature data are not available in many of Australia's cropping areas. A model is therefore needed to simulate suitable temperature data for research and management applications. A suitable computer model using readily available soil and climatic data to calculate hourly soil temperatures is presented for this purpose. The model was identified in the literature and modified for use with a Ug5.2 clay soil under conditions of bare fallow and with a wheat crop. Field data for modifying and validating the model were obtained from a trial site in the Wimmera wheat growing region of Victoria, Australia. Validation results for the modified model (designated the ASTC model) are presented, based on recorded temperatures over a 1-month period on the surface and at 50 mm depth in the soil profile. The model predicted the soil temperature at 50 mm depth under a bare surface with a standard error of estimate (SEE) of 2.4°C during validation. The corresponding value with a wheat crop was 2.1°C. While simulating the entire period of recorded temperatures the ASTC model had average hourly prediction errors of 2.1°C with the bare fallow (4-month period) and 1.1°C with the wheat crop (4-month period) at 50 mm depth. The standard errors of estimate for the predicted temperatures in the extended application of the model varied from 1.9°C at 50 mm depth to 0.2°C at 500 mm depth with the wheat crop. Corresponding SEE values with the bare fallow ranged from 3.0 to 0.4°C.     

Does history matter? Temperature effects on soil microbial biomass and community structure based on the phospholipid fatty acid (PLFA) analysis

Background, aim, and scope

Temperature is an important environmental factor regulating soil microbial biomass, activity, and community. Soils from different climatic regions may have very different dominant soil microbes, which are acclimated to the local conditions like temperature. Changing soil temperature especially warming has been shown to increase the mortality rate of soil microbes. However, little is known about the responses of soil microbes coming from different climatic regions to different incubation temperatures. The objective of this study was to examine the temperature effects on microbial biomass and community of soils collected from cold, intermediate, and hot natural sites.

Materials and methods

Soils were collected from northern (Heilongjiang province), central (Jiangsu province), and southern (Guangxi province) China, these soils having very different temperature histories. The Heilongjiang soil was from the coldest region with a mean annual temperature of 1.2°C, the Jiangsu soil was intermediate with a mean annual temperature of 15.7°C, and Guangxi soil was from the hottest area, with a mean annual temperature of 21.2°C. These three soils were incubated at 4°C, 15°C, 25°C, and 35°C for up to 56 days. Phospholipid fatty acid (PLFA) analyses were conducted on days 0, 3, 7, 14, 28, and 56 to track the dynamics of soil microbes.

Results

Soil microbial biomass indexed by total phospholipid fatty acid concentration decreased with increasing incubation temperature, with that of the Heilongjiang soil decreasing most. At the end of incubation, the biomass at 35°C in the Heilongjiang, Jiangsu, and Guangxi soils had declined to 65%, 72%, and 96% of the initial biomass, respectively. The PLFA patterns shifted with increasing temperatures in all the soils, especially at 35°C; the change was biggest in the Heilongjiang soil.

Discussion

History does have effects on soil microbes responding to environmental stress. Soil microbial biomass and PLFA profiles shifted least in the Guangxi soil with the hottest temperature history and most in the Heilongjiang soil with the coldest temperature, indicating that the distribution of free-living microorganisms is influenced by climatic factors. The majority of soil microorganisms coming from the hot regions are more adapted to high temperature (35°C) compared to those from the cold area. There are some regular changes of PLFA profiles when increasing incubation temperature to 35°C. However, the effect of incubation temperature on soil microbial community structure was inconclusive. As PLFA profile community structure is the phenotypic community structure. Genotype experiments are required to be done in future studies for the better understanding of soil microbes in different climate regions with concerning temperature variation.

Conclusions

With the increasing incubation temperature, soil microbial biomass and PLFA profiles shifted most in the soil with the coldest temperature history and least in the soil with the hottest temperature. History does matter in determining soil microbial dynamics when facing thermal stress.     

Seasonal effects on photoassimilated carbon-14 in the root system of blue grama and associated soil organic matter

Blue grama (Bouteloua gracilis (H.B.K.) Lag.) was grown at day (14 h) and night temperatures of 25° and 15°C, respectively, in a ¹⁴CO₂-atmosphere during the last 31 of the 55 days from germination to seed set (period 1). An air-tight seal separated the shoot and root spheres. This period was followed by 21 days of a 14°C day (10 h) and 38°C night regime, and 29 days of continuous ?5°C (period 2), and 26 days of the original temperature and light conditions (period 3). Distribution of the assimilated ¹⁴C at the end of period 1 was: roots 33%; root-derived organic matter in the soil 23%; and 22% was released as CO₂. The washed root mass to root-derived soil organic matter ratio of the labelled ¹⁴C was 60 to 40. A root mass decrease of 45% over the cool and frost period changed this ratio to 23 to 77. Polysaccharides and 0.1 n NaOH-extractable organic matter decreased while potential dehydrogenase activity and total organic P increased during this same period, thereby confirming field related observations. Measured dehydrogenase activity overwinter may have two different origins. As total C content of the soil did not increase under the conditions of the experiment, it was postulated that a portion of the observed increase in total C in the field overwinter was of inorganic rather than organic origin.     

Field and incubation temperature effects on mobilization of nitrogen,phosphorus and potassium in peat

Calluna-derived, amorphous H-horizon material from a peaty ferric stagnopodzol was incubated at two constant temperatures: 6° and 20°C and at two fluctuating temperatures: alternating days at 6° and 20°C and at field fluctuating temperatures. After 3 weeks, amounts of mobilized N, P and K at 6°, 20°C and field temperatures were higher than before incubation. Incubated peat at temperatures of 6° and 20°C on alternating days for 3 weeks produced smaller amounts of deionized-distilled water-extractable NH₄⁺-N, P and K than before incubation. For N, P and K, incubation at constant high temperature (20°C) produced similar amounts of mobilized nutrients compared to field surface soil temperatures.The magnitude of deionized-distilled water-extractable N and P in experimental treatments followed a similar sequence: 6°C incubation > field temperatures > 20°C incubation > before incubation > imposed fluctuating 6° and 20°C temperatures. For K, the mobilization sequence was slightly different: 6° incubation > 20°C incubation > field temperatures > before incubation > imposed fluctuation 6° and 20°C temperatures.     

Decomposition and nitrogen dynamics of litter in peat soils from two climatic regions under different temperature regimes

Soil temperature is a major factor affecting organic matter decomposition and thus, global warming may accelerate decomposition processes. However, it remains unclear whether the effects will be similar in climatically different regions. The effects of soil temperatures of 5, 10 and 15 °C on the decomposition of Scots pine (Pinus sylvestris L.) needles were assessed in a 1-year (360 days) growth chamber experiment. Intact peat cores from two climatically different peatland sites (southern and northern Finland) were used as the incubation environments. Needles were incubated in litter bags beneath the living moss layer, and mass loss and nitrogen (N) concentration were determined at 60-day intervals. The rate of mass loss from the needles over time was clearly lower in the 5 °C treatment than at the higher temperatures. Mass loss was strongly related to the accumulated soil temperature sum. In temperatures higher than 5 °C, mass losses were higher in the northern peat. Also, the limit value of decomposition (asymptotic maximum mass loss) was slightly higher in the northern peat (92%), than in the southern peat (87%). The N concentration increased up to a mass loss of 50–60%, whereupon it decreased, while the amount of N (as a percentage of the original amount) remained unchanged until a mass loss of 50–60%, whereupon it decreased linearly. It seems that increasing soil temperatures may result in slightly higher rates of needle litter mass loss and consequent N release in northern peat than in southern peat. The faster decomposition in higher temperatures in the northern peat, together with the slightly higher maximum mass loss value, imply that with climatic warming, susceptibility of boreal peatlands for becoming sources of carbon to the atmosphere may increase towards north.     

Effects of warming, wetting and nitrogen addition on substrate-induced respiration and temperature sensitivity of heterotrophic respiration in a temperate forest soil

Soil heterotrophic respiration and its temperature sensitivity are affected by various climatic and environmental factors.However,little is known about the combined effects of concurrent climatic and environmental changes,such as climatic warming,changing precipitation regimes,and increasing nitrogen(N)deposition.Therefore,in this study,we investigated the individual and combined effects of warming,wetting,and N addition on soil heterotrophic respiration and temperature sensitivity.We incubated soils collected from a temperate forest in South Korea for 60 d at two temperature levels(15 and 20℃,representing the annual mean temperature of the study site and 5℃warming,respectively),three moisture levels(10%,28%,and 50%water-filled pore space(WFPS),representing dry,moist,and wet conditions,respectively),and two N levels(without N and with N addition equivalent to 50 kg N ha^-1year^-1).On day 30,soils were distributed across five different temperatures(10,15,20,25,and 30℃)for 24 h to determine short-term changes in temperature sensitivity(Q₁₀,change in respiration with 10℃increase in temperature)of soil heterotrophic respiration.After completing the incubation on day 60,we measured substrate-induced respiration(SIR)by adding six labile substrates to the three types of treatments.Wetting treatment(increase from 28%to 50%WFPS)reduced SIR by 40.8%(3.77 to 2.23μg CO₂-C g^-1h^-1),but warming(increase from 15 to 20℃)and N addition increased SIR by 47.7%(3.77 to 5.57μg CO₂-C g^-1h^-1)and 42.0%(3.77 to 5.35μg CO₂-C g^-1h^-1),respectively.A combination of any two treatments did not affect SIR,but the combination of three treatments reduced SIR by 42.4%(3.70 to 2.20μg CO₂-C g^-1h^-1).Wetting treatment increased Q₁₀by 25.0%(2.4 to 3.0).However,warming and N addition reduced Q₁₀by 37.5%(2.4 to 1.5)and 16.7%(2.4 to 2.0),respectively.Warming coupled with wetting did not significantly change Q₁₀,while warming coupled with N addition reduced Q₁₀by 33.3%(2.4 to 1.6).The combination of three treatments increased Q₁₀by 12.5%(2.4 to 2.7).Our results demonstrated that among the three factors,soil moisture is the most important one controlling SIR and Q₁₀.The results suggest that the effect of warming on SIR and Q₁₀can be modified significantly by rainfall variability and elevated N availability.Therefore,this study emphasizes that concurrent climatic and environmental changes,such as increasing rainfall variability and N deposition,should be considered when predicting changes induced by warming in soil respiration and its temperature sensitivity.     

The influence of temperature on the growth and sulfur uptake of oats (Avena sativa L.)

Abstract

Oats were grown in perlite and nutrient solution at temperatures varying from 10/5°C (day/night) to 36/31°C. The optimum temperature for growth of tops was found to be 27°C day/22°C night over an eight week period. Plant S content showed an inverse relationship with yield.

Uptake of S was low at low temperature (10/5, 15/10°C), but was balanced by retarded growth at this temperature. Hence, uptake did not restrict growth at low temperature.     

Effect of soil solarization on subsequent nitrification activity at elevated temperatures

Soil solarization is a nonchemical method of soil disinfection achieved by covering the soil surface with sheets of vinyl plastic to generate elevated soil temperature, generally over 45°C. Such elevated temperatures may be detrimental to some nitrifying microorganisms and favorable to others. However, little information exists to indicate how nitrification activity in soil is affected after solarization. We performed several experiments to investigate the effects of soil solarization on nitrification activity. We found that: (1) if a soil was subjected to pretreatment of 45 or 50°C for as little as 1 d, nitrification activity in a subsequent incubation at 30°C was less than that of a soil that did not receive any high-temperature pretreatment. However, if a soil received pretreatments of 45 or 50°C for more than 7 d, nitrification activity in a subsequent incubation at 45 or 50°C was greater than that of soil that did not receive high temperature pretreatment. (2) Nitrification activity in three kinds of soil taken from 0–5 cm depth after solarization treatment was greater at 45°C than 30°C. (3) Nitrification activity at 45°C in soil that had received solarization in the preceding year was greater than that in soil that had not been subjected to solarization. This was consistent with the fact that the population densities of ammonia oxidizers were greater in soils that had been subjected to solarization. These results suggest that soil solarization induces nitrifying microorganisms that are more active at 45–50°C than they are at 30°C, and that the effect of solarization on nitrification persists until the next crop season.     

Temperature effects on ammonification and nitrification in a tropical soil

Ammonification of soil organic N and nitrification of ammonium-N was studied in Tindall clay loam over a range of temperatures from 20–60 C. Nitrification rates at each temperature were constant throughout the 28 day incubation, whereas most of the ammonification occurred in the first 7 days. The optimum for nitrification was close to 35 C. exhibiting a sharp peak at this temperature at which the potential rate was 4.8 μg N/g day^?1, compared with 0.5 μg N/g day^?1 at 20°C and 0.25 μg N/g day^?1 at 60°C. The optimum temperature for ammonification was approximately 50°C at which the rate was 2.8 μg N/g day^?1 in the first 7 days but only 0.5 μg N/g day^?1 between 14 and 28 days.The temperature responses could be described mathematically with functions of the type log_oN = k × 1/T.The results are discussed in relation to daily patterns of N mineralization in the field where temperatures show diurnal fluctuation.     

Time-temperature relationships for the inactivation of sclerotia oF Sclerotium oryzae

The viability of sclerotia of Sclerotium oryzae was tested in both wet and dry soil under simulated elevated temperatures in either constant, cyclic or short temperature regimes. In wet soil viability was reduced to zero by a constant temperature of 45°C and above for 1 day or a minimum oven temperature of 55°C for 2 h. Viability of sclerotia were destroyed by either a 10-day constant temperature of 40°C or a 2-h temperature cycle for 3 days at 50°C or 12 days at 45°C. Below 40°C sclerotia were not affected. In dry soil at 60°C, a 3-day constant temperature or a 12 days 2-h temperature cycle eliminated sclerotial viability. Data on time and temperature relationships on loss in viability of sclerotia in soil could thus be used to predict efficacy of soil solarization.     

Influence of temperature on the growth of bermudagrass selections from the Appalachian region

Abstract

The hilly terrain of the Appalachian region creates an environment in which large differences in soil temperature occur over a very short distance on the landscape. The ability of a grass to display adequate growth over a range of temperatures would greatly enhance its adaptability and use as a forage or for soil conservation. A growth chamber experiment was conducted to evaluate the influence of temperature on the growth of six bermudagrass [Cynodon dactylon (L.) Pers.] selections from the Appalachian region. Midland, a cold tolerant bermudagrass, was included in the study for comparison purposes. The grasses were grown under a 14 hour day length with three day/night temperature regimes: 18°C/13°C, 27°C/21°C, and 35^OC/29°C. Two of the selections had significantly higher dry matter production than Midland over the range of temperatures.

This effect was especially pronounced at 35°C where the top growth of Quicksand common and Selection 13 exceeded that of Midland by 206% and 158%, respectively. The higher yielding selections were comparable to the other bermudagrasses when mineral concentrations, neutral detergent fiber, acid detergent fiber and acid detergent lignin levels were considered. Both Quicksand common and Selection 13 seem to have the potential to be particularily useful on south facing slopes where elevated soil temperatures are encountered.     

Environmental Monitoring Using Physiological Telemetry – A Case Study Examining Common Carp Responses to Thermal Pollution in a Coal-Fired Generating Station Effluent

During the winters of 1998 and 1999, the response of common carp (Cyprinus carpio) to fluctuating thermal conditions was studied in the Nanticoke Thermal Generating Station discharge canal on Lake Erie. Locomotory activity of fish in the canal was monitored using electromyogram telemetry of the axial musculature. Carp activity was variable but, in general, they were more active during times of rising and falling temperatures, and were least active during stable periods. The magnitude of water temperature fluctuation was not correlated with activity. Locomotory activity of fish was not generally correlated with absolute water temperature over a wide range of temperatures (～2 to 18 °C) when examined on an hourly basis, but was moderately correlated at a finer temporal resolution (5 min). During a station shutdown, one carp stayed in the canal and experienced a substantial decrease in temperature yet exhibited no significant change in activity. The results of this study suggest that minor temperature changes (～0.1 °C per hour) are sufficient to alter activity, probably through fine scale behavioral thermoregulation. The heightened activity resulting from slight changes in temperature may be energetically costly in environments that change as rapidly as thermal effluents. Physiological telemetry permitted us to study the in situ response of fish to dynamic environmental conditions with more precision than is possible using locational telemetry. We suggest that physiological telemetry can provide insights into the behavioral and physiological responses of fish to a diversity of pollutants and represents a robust environmental monitoring technique.     

Colonization of buried cotton stems by microarthropods

Initial colonization of cotton stems by microarthropods proceeded more rapidly while buried in soil under laboratory conditions (20–23°C) than while buried in the field during the winter months when soil temperatures ranged from 5–10°C in the study area in the San Joaquin Valley of California. While 15 species were found frequently in cotton stems held in the laboratory for 20 weeks, only seven species were found in field buried stems. Arthropods found under both conditions were a species of pyemotid mite; an astigmatid mite, Tyrophagus dimidiatus; two collembolans, Proisotoma minuta and Tullbergia sp.; and a sciarid fly larval stage, Bradysia impatiens. Even though the soils at teh field sites possessed a number of microarthropods in common, the stem colonization at each site was restricted to a single group which differed from each of the other sites. Microenvironments affect stem colonization patterns by microarthropods but microarthropods did not appear to have a significant influence on early cotton stem decomposition rates nor was there evidence that their activities reduced Verticillium microsclerotia populations.     

The uptake and translocation of phosphate by mycelial strands of pine mycorrhizas

Uptake and rapid translocation of ³²P-orthophosphate to Pinus radiata mycorrhizas from soil by mycelial strands of Rhizopogon luteolus was demonstrated. In greenhouse material, translocation occurred from soil for at least 12 mm and some 30–80 per cent of phosphate absorbed from 5 × 10^?6M as KH₂PO₄ was translocated. In the field, translocation occurred for 12 cm. Uptake by excised mycelial strands was metabolically mediated. Translocation occurred more rapidly when the untreated ends of strands were placed in an osmoticum: polarity in translocation was also observed. It was concluded that uptake and translocation by mycelial strands (as distinct from individual hyphae) provide an effective method for mycorrhizal exploitation of large inter-root soil volumes and assist the plants in competition for nutrients.Large differences occurred between strains of the same species in mycelial strand growth in soil. Mycelial strands of R. luteolus grew through the test soil at 1.3-2.9 mm/day and along P. radiata roots at 1.7 mm/day at 25°C day and 16°C night temperatures.