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41.
Summary Inland and sea cliff populations of bothAgrostis stolonifera L. andHolcus lanatus L. were subjected to soil NaCl treatments, of 100 and 200 mol m−3 NaCl, and tolerance examined using plant dry weight data. A parallel experiment subjected them to salt spray treatments of
2.5%, 5% and 10% NaCl in distilled water, and tolerance assessed from leaf damage.
Both populations of each species were equally sensitive to soil NaCl. When subjected to salt spray the sea cliff populations
however showed marked resistance to leaf damage. Soil salinity resistance and salt spray resistance thus appear to be independent
characteristics in these two species. 相似文献
42.
Soil respiration of Alaskan tundra at elevated atmospheric carbon dioxide concentrations 总被引:3,自引:0,他引:3
Summary CO2 efflux from tussock tundra in Alaska that had been exposed to elevated CO2 for 2.5 growing seasons was measured to assess the effect of long- and short-term CO2 enrichment on soil respiration. Long-term treatments were: 348, 514, and 683 μll−1 CO2 and 680 μll−1 CO2+4°C above ambient. Measurements were made at 5 CO2 concentrations between 87 and 680 μll−1 CO2. Neither long- or short-term CO2 enrichment significantly affected soil CO2 efflux. Tundra developed at elevated temperature and 680 μll−1 CO2 had slightly higher, but not statistically different, mean respiration rates compared to untreated tundra and to tundra under
CO2 control alone. 相似文献
43.
Curt Leben 《Plant and Soil》1986,91(1):139-142
Summary Survival ofPseudomonas syringae pv.lachrymans with seedling cucumber roots, root washings, rhizosphere soil, and nonrhizosphere soil was determined 7–8 days after the soil surface was watered with a cell suspension of the bacterium. Plants were in pots in the green-house and soil was not sterilized. Survival was best with roots and root washings, next best in rhizosphere soil, and poor in nonrhizosphere soil. 相似文献
44.
Summary Studies on levels of lead and cadmium of Indian flue-cured tobacco indicated that the leaf contained very low amounts of these
heavy metals as compared to tobacco from other countries. Indian tobacco can therefore be adjudged as ‘safe and clean’ and
least hazardous to the smoker. Of the two heavy metals, lead content of soils is higher than cadmium. But in the leaf, cadmium
content is more than lead indicating that soil cadmium may be more available to tobacco and hence more readily absorbed by
the plant than lead. 相似文献
45.
Summary Our field surveys conducted in 10 Hungarian grape producing areas have revealed that the nutrient contents of vine leaves of different grape varieties were closely correlated with the EUF-nutrient contents of different soil types with different contents of clay. Resulting from these relationships the following EUF-nutrient values are considered as required for optimal nutrition of the vine-stock to attain grape yields of 10–12 t/ha in the areas under investigation: 相似文献
46.
Nature and properties of humic acid prepared from different sources and its effect on nutrient availability 总被引:1,自引:0,他引:1
Summary Effect of sources, moisture levels and extractants on extraction, analytical properties, IR-spectra, macromolecular characteristics, interaction with cations and physiological properties of the extracted material (humic acid) were studied. Among the three variables, extractant influenced the degree of humification, IR-spectra, nature and properties of humic acids to a greater extent though the other two had significant contribution. Sodium pyrophosphate found to be an ideal extractant for humic acid. Reduced viscosity of humic acids increased with dilution particularly below 0.1 g/dl and decreased with increasing H+ concentration between pH 6.5 and 8.5 irrespective of source, moisture level and extractant. The amount of proton released and drop in initial pH of humic acids on addition of different metal ions indicated formation of mono-, di-hydroxy metal-HA complexes which broke down at pH 8.0 and above. HA-Fe2+ and HA-Cu2+ complexes were found to be most stable. Humic acids from different sources varied significantly in their effect on available nutrient status of soils though, the latter is main determining factor particularly for calcium and magnesium. 相似文献
47.
J. Loch 《Plant and Soil》1985,83(1):77-83
Summary On the basis of pot experiments carried out on soils with different Mg contents using ryegrass, it could be established that Mg uptake by ryegrass is closely related to Mg in the EUF extracts. The Mg contents in the EUF extracts are therefore suitable indices of actually and potentially available Mg in soils.The ratio between Mg in the EUF extracts and Mg deposited on the electrode + filter varies. The absolute amount of Mg in the EUF extracts increases with increasing Mg content of the soils. The higher, however, the total desorbable Mg the lower are the Mg contents in the EUF extracts in comparison with the Mg contents deposited on electrode + filter. Besides total desorbable Mg the EUF-Mg fractions are influenced as well by the organic and inorganic CEC and by soil pH. The amount of EUF filtrate flowing through filter and electrode also has an influence on the amount of Mg in the EUF filtrate.Consequently for a proper evaluation of available soil Mg total EUF-Mg (Mg in the EUF filtrate + Mg deposited on electrode + filter) should be used. 相似文献
48.
Summary Root hairs have been shown to enhance P uptake by plants growing in low P soil. Little is known of the factors controlling root hair growth. The objective of this study was to investigate the influence of soil moisture and P level on root hair growth of corn (Zea mays L.). The effect of volumetric soil moistures of 22% (M0), 27% (M1), and 32% (M2) and soil (Raub silt loam, Aquic Argiudoll) P levels of, 0.81 (P0), 12.1 (P1), 21.6 (P2), 48.7 (P3), and 203.3 (P4) mol P L–1 initially in the soil solution, on shoot and root growth, P uptake, and root hair growth of corn was studied in a series of pot experiments in a controlled climate chamber. Root hair growth was affected more by soil moisture than soil P. The percentage of total root length with root hairs and the density and length of root hairs on the root sections having root hairs all increased as soil moisture was reduced from M2 to M0. No relationship was found between root hair length and soil P. Density of root hairs, however, was found to decrease with an increase in soil P. No correlation was found between root hair growth parameters and plant P content, further suggesting P plays a secondary role to moisture in regulating root hair growth in soils. The increase in root hair growth appears to be a response by the plant to stress as yield and P uptake by corn grown at M0 were only 0.47 to 0.82, and 0.34 to 0.74, respectively, of that measured at M1 across the five soil P levels. The increase in root hair growth at M0, which represents an increase of 2.76 to 4.03 in root surface area, could offset, in part, the reduced rate of root growth, which was the primary reason for reduced P uptake under limited soil moisture conditions.Journal Paper No. 10,066 Purdue Univ. Agric. Exp. Stn., W. Lafayette, IN 47907. Contribution from the Dep. of Agron. This paper was supported in part by a grant from the Tennessee Valley Authority. 相似文献
49.
Modelling growth responses of soil nitrifiers to additions of ammonium sulphate and ammonium chloride 总被引:1,自引:0,他引:1
Summary Following the addition of 0–75 mole N g–1 as ammonium chloride or ammonium sulphate to a sandy loam soil the nitrate formed was measured daily for a period of 15–17 days. The nitrate produced as a function of time was described using the Monod equation for microbial growth. An optimisation technique is described for obtaining, from the nitrification time course data, the maximum specific growth rate, the affinity constantant and an index limited by the concentration of ammonium in soil solution. Additions of more than 7.3 moles N g–1 soil as ammonium chloride were found to inhibit nitrification. The inhibition was interpreted as being caused by osmotic pressure or by chloride ion. A similar effect was not found with ammonium sulphate, because the salt concentration in the soil solution was restricted by the precipitation of calcium sulphate. The model developed was capable of accounting for nitrate production in the soil under non-steady state conditions of substrate concentrations and nitrifier biomass. 相似文献
50.
Jack T. Trevors 《Applied microbiology and biotechnology》1985,23(2):152-155
Summary The influence of different O2 concentrations on denitrification was studied in an agricultural soil. In both nitrate and nitrite amended soil, denitrification was not observed until the O2 concentration decreased to 0.20 and 0.21 mol/ml, respectively. Denitrification was not observed in soil samples with O2 concentrations above 0.28 mol/ml in the gas phase. These findings suggest that a completely anoxic environment is not required for denitrification to occur in soil. 相似文献