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1.
Studies were carried out in the glass house using sand culture to find out the specific ion effect on the accumulation of abscisic acid in wheat. Seeds were sown in sixteen different solutions of chloride, sulphate, nitrate, carbonate salts of sodium, potassium, calcium and magnesium used each at ‐2 bar osmotic potential. The leaf samples taken after 25 days of sowing indicated that osmotic as well as salt stress increased significantly the accumulation of abscisic acid. The accumulation of abscisic acid was significantly less under potassium and calcium salt ions as compared to that under sodium and magnesium salts ions. Overall effect of anions showed that accumulation of abscisic acid was more under PEG (osmotic stress and chloride salts but it was less under sulphate and nitrate salts and was the least under carbonate salts. The accumulation of abscisic acid was exceptionally high under potassium dihydrogen phosphate. In general, the accumulation of abscisic acid‐a growth inhibitor varied not only with the type of the cation but also depended on the accompanying anion indicating differential growth response of plants under different types of saline conditions having dominance of different salt ion(s).  相似文献   

2.
Abstract

The interactions of major cations (K,Ca,Mg) are studied in Sorghum (Sorghum dochna F.); the nutritive solutions are deficient or not, in magnesium. The mineral contents of the plants grown on the reference solution are compared to those of two solutions, in which magnesium is replaced by calcium or potassium. The limit threshold of deficiency does not affect the yield of plants, but reduces strongly the content of magnesium. On the other hand, no variation of calcium is observed since the magnesium substitution is effected by potassium. The experiments do not clearly show a Mg/Ca interaction in Sorghum.  相似文献   

3.
It has been shown that the distribution features of the hydrophilic and hydrophobic fractions of humic substances (HSs) in the upper genetic horizons of undisturbed podzolic soils and litho-barrier podzols are similar. The concentrations of the separate HS fractions in the mineral horizons are largely determined by the soil mineralogy. In forest litters of secondary phytocenoses developed after the cutting of spruce forests, an increase in the content of hydrophilic compounds has been observed on loamy deposits at a decrease in the portion of lignin-like organic compounds. An increase in the portion of Al-Fe-humus compounds has been revealed in the mineral soil horizons of secondary phytocenoses. It has been proposed to use the degree of hydrophilicity (D H ) for characterizing the features of the organic matter in taiga soils. An increase in the content of the fractions of occluded organic matter and that bound to minerals (density of 1.6–2.2 g/cm3) has been observed in the eluvial horizons of a young cutover area.  相似文献   

4.
Xylem sap plays a major role in long‐distance transport of water, nutrients, and metabolites. However, there is little information on the behavior of metabolites in mineral‐deficient xylem sap. For this reason, the time‐dependent changes in selected metabolites (amino acids, organic acids, and soluble sugars) from tomato xylem sap in response to nitrogen (N), phosphorus (P), or potassium (K)‐deficient condition were investigated. Tomato plants (Solanum lycopersicum L.) were grown hydroponically in liquid culture under three different mineral regimes: N‐deficient [0.5 mM Ca(NO3)2 and 0.5 mM KNO3], P‐deficient (0.05 mM KH2PO4), and K‐deficient (0.5 mM KNO3), respectively. Xylem sap was collected at 10:00 am after 1, 5, 15, and 30 d, and the selected metabolites were analyzed with liquid chromatography. All N, P, or K deficiencies led to a substantial increase in metabolites in the xylem sap. The predominant amino acid in the xylem sap was glutamine and, interestingly, all mineral deficiencies resulted in a substantial amount of γ‐aminobutyric acid (GABA). Additionally, organic acids (citrate and malate) and soluble sugars were strongly increased in all mineral deficiencies, and, in particular, the level of shikimate was greatly affected by N deficiency. Based on these data, it is necessary to clearly elucidate an unknown event taking place in xylem loading in a variety of environmental impacts, and we are now studying to expand our knowledge on metabolic and proteomic responses using GC‐MS and LC‐MS.  相似文献   

5.
长期施肥下红壤有机碳及其颗粒组分对不同施肥模式的响应   总被引：15，自引：3，他引：12  
采集不同施肥24年的红壤,采用物理分组的方法,观测了长期不同施肥下红壤有机碳及其组分变化,并结合历史资料分析了不同施肥模式对红壤有机碳及其颗粒组分的影响。结果表明,化肥配施有机肥（NPKM）处理下红壤总有机碳含量（10.33 g/kg）,砂粒（2000～53 m）、细粉粒（5～2 m）和粘粒（2 m）组分中的有机碳含量显著高于其他处理。与不施肥（CK）相比,施用化肥（NPK、2NPK）和有机肥（NPKM、M）显著地提高了红壤有机碳在砂粒和粘粒中的分配比例,而降低了其在粗粉粒和细粉粒的分配比例。施化肥（NPK、2NPK）、单施有机肥（M）、化肥配施有机肥（NPKM）处理,土壤有机碳的平均固定速率分别为0.05 t/(hm2?a)、0.18 t/(hm2?a)、0.26 t/(hm2?a)。相关分析表明,不同施肥模式下红壤有机碳的固定量与碳投入量之间存在着极显著的线性相关关系（R2=0.909, P0.01）,土壤的固碳效率为8.1%;随着碳投入的增加,粗粉粒和细粉粒有机碳储量逐渐下降,而砂粒和粘粒中碳储量逐渐增加,并且粘粒增加速率要远远高于砂粒。以上结果说明,红壤中有机碳还没有达到饱和,还具有一定的固碳潜力,增加的有机碳主要固持在粘粒中,粘粒是红壤有机碳的主要固持组分。  相似文献   

6.
The previous work (1) with bleeding sap from taro plants grown in solution culture at varying ammonium sulphate application under aerobic condition revealed that a potassium deficiency led to a contradictory relationship of the variation in amino-N content in bleeding sap to the exudation rhythm; in the earlier period of bleeding experiment a deficient K-application decreased the amino-N content but accelerated the exudation rate. In this connection, there are good reasons for believing that the passage of water and salts into the xylem ducts is largely controlled by the metabolic conditions in adjacent living cells, especially their rate of aerobic respiration (2). Therefore, the effects of potassium nutrition on the exudation phenomenon were reexamined with taro plants grown in solution culture under nitrate nutrition and correlated with information about the effect of aeration through culture medium during bleeding experiment on the rate of exudation and contents of nitrogenous constituents of bleeding sap. Arsenite- or DNP-treatment was also carried out in vivo with the roots in order to elucidate a possible relationship between the respiration in roots and the exudation process of xylem sap.  相似文献   

7.
Abstract

A second rotation forest sand (Mt Burr sand) was separated by a combination of dry sieving and winnowing into different particle sizes rich in either soil or organic matter. These fractions were analysed for % loss on ignition, % organic carbon, total organic nitrogen and mineral nitrogen. Mineralization of soil organic nitrogen and nitrification of ammonium sulphate added to these fractions were studied. Amongst the heavier fractions obtained by sieving, the <125 μm fraction (the finest) contained the highest concentration of organic and exchangeable nitrogen and was the most active in nitrogen transformations. Amongst the lighter fractions obtained by winnowing, the 125 to 500 μm fraction had the highest organic nitrogen content but mineralization of nitrogen was greatest in the 500 to 2000 μm. Nitrification of native and applied ammonium nitrogen was similar in both the 125 to 500 μm and 500 go 2000 μm organic matter fractions.  相似文献   

8.
Pot culture experiments are described which attempt to identify the organic fractions of soil sulphur that decompose during the growing season to provide plant-available sulphur.Soil organic matter was labelled with 35S by incubating soil with labelled sulphate and several organic sulphur fractions were determined before and after the growth of Sorghum vulgare and following a fallow treatment. The effect of moisture stress on the uptake of sulphur by plants was also investigated; this treatment had little effect.Changes occurred in both hydriodic acid-reducible and carbon-bonded sulphur fractions, 60 per cent of the sulphur taken up by the plants being derived from the latter. The changes in carbon-bonded sulphur involved changes in both Raney nickel-reducible and non-reducible sulphur fractions. All of the sulphur fractions investigated thus contributed available sulphur for plant uptake, and none of them are likely to be of any value for predicting the sulphur requirements of plants.  相似文献   

9.
Plant cell adjustments in water and osmotic status in response to heat, cold, and osmotic stress were investigated using microcultured plants from four assessions of Lycopersicon. Changes in plant water potentials were determined with an osmometer solution method, and osmolarity by a cell sap extraction method. Heat stress decreased water potential (raised osmolarity) and cold stress increased water potential (depressed osmolarity) for all species, but the magnitude of the adjustment was significantly greater for L. peruvianum (a drought resistant genotype). Microcultures produced on growth medium with elevated levels of osmotic agents (sorbitol, dextran, or glucose) developed correspondingly higher cell sap osmolarity. Plant water potential shifted in the same direction, but not to the same degree, as osmotic potential in response to stress. Since osmotic adjustment is a reported mechanism of stress (salt, temperature, and water deficit) tolerance, these tests suggest a method for prescreening of germplasm at the microculture plant level.  相似文献   

10.
Eight organic and either inorganic magnesium (Mg) compounds (sulphate, acetate, caproate, laurate, glycine salt, L‐valine salt, L‐phenylalanine salt, and ethylene‐diaminetetraacetic acid magnesium disodium salt) were tested for Mg resorption from the leaf surface of oats (Avena sativa L. cv. Zlat'ák) and for biological availability. The plants were grown on Mg‐deficient Hoagland nutrient solution. Significant differences among the alternatives studied were found through one‐way ANOVA in all parameters of plants (top and root dry weight, Mg content in tops and roots, chlorophyll a and b content and top height). A very significant decrease of Mg content in plants and aggravation of the plant health status with increasing molar weight value (Mr) of anhydrous compound used in corresponding experimental alternative was observed. The best results were obtained in the case of magnesium sulphate (MgSO4.7H2O) (the lowest Mr value) while the worst were observed in the case of Mg laurate. A different diameter of the biggest particle necessary to be absorbed with Mg (Mg complex molecule/anion, salt anion) resulting in different mobility of this particle in water solution was proposed to be the main reason of this effect. This diameter is closely related to the Mr value of the particular compound in this case. Surprisingly, no effect of fertilizer polarity on Mg penetration was observed. The effect of complex stability of some Mg compounds on Mg penetration was also investigated. The biological availability significantly decreased with the increase of the complex strength.  相似文献   

11.
Soil organic carbon(SOC) and nitrogen(N) mineralization are important biogeochemical processes associated with soil fertility. These processes are influenced by physically, chemically, and biologically stabilized SOC fractions, the mechanisms of which are not well known. The present study was conducted to evaluate the combined effect of manure and mineral fertilizers on the contents of SOC fractions to promote the mineralization of SOC and N.Treatments included: i) no fertilizer control(CK); ii)...  相似文献   

12.
Abstract

This article describes a modified compulsive exchange method suitable for the determination of cation exchange capacity (CEC) over a pH range on solid, separated organic‐matter fractions. The method is demonstrated to be a reproducible and relatively simple means of measuring CEC on fractions separated by physical means in conjunction with hydrofluoric acid (HF) treatment. By including a modification for measuring the residual magnesium (Mg2+) content by dilution and conductivity, the method is simplified to measure CEC versus pH using a single sample; the only laboratory instruments required are pH and conductivity meters and a balance. The lack of agreement between this method and the silver thiourea (AgTU) method for some fractions at low pH is attributed to the uncontrolled variation in solution ionic strength when acid is introduced to effect solution pH changes in the AgTU method.  相似文献   

13.
The effect of liming on organic matter in sandy loamy soddy-podzolic soil was studied. The study was performed on samples taken from the 50-year-long experiment established by Prof. Kornilov in 1957. It was shown that liming had almost no effect on the total humus content in the soil. The humus composition was studied using two fractionation methods of the humus substances by the Ponomareva-Plotnikova procedure. The regrouping of the humus fractions occurred due to the changes in the mobility of soil mineral components, which involved a regular increase in the content of the Ca-bound fraction of humic acids (HA-2) at the expense of the HA-1 fraction bound to the mobile forms of R2O3 reliable at the lime rates equivalent to the total acidity and higher. The levels of the stabilization of the different HA fractions were considered, as well as the stability of the changes in the humus composition during 50 years.  相似文献   

14.
Climate change is predicted to reduce or delay annual wintertime snow pack formation in the forests of the northeastern US. Any delay in snowpack formation could increase soil freezing in winter and, thereby, alter soil characteristics and processes. We examined the hypothesis that delayed snowpack would disrupt soil structure and change organic matter bioavailability in an experimental snow removal study at the Hubbard Brook Experimental Forest (HBEF), NH, USA. Pairs of reference and snow removal treatment plots were studied in four different sites at HBEF. Snow was removed from November–January of two winters, inducing soil freezing throughout both winters. Size class distribution and organic matter concentration and content of aggregates, and carbon and nitrogen mineralization potential of size fractions were quantified for surface mineral soils in the spring of both years immediately after snowmelt. In the first year of sampling, the only significant effect of snow removal was an increase in the smallest (<53 μm) size fraction of mineral soil. In the second year, snow removal increased organic matter concentrations of macroaggregate (250–2,000 μm) and microaggregate (53–250 μm) size fractions. This change corresponded to an increase in net N mineralization potential and the ratio of N to C mineralized in the macroaggregate fraction, but there were no effects of snow removal on C mineralization. We propose that soil freezing increases the movement of organic matter from organic to mineral soil horizons and increases the N content of mineralizable substrates in mineral soil following years with delayed snowpack formation.  相似文献   

15.
The effects of the commonly used processing techniques of soaking (at different pH values) and cooking on the digestive and nutritive utilization of calcium, phosphorus, and magnesium from common beans (Phaseolus vulgaris L.) were studied. Before the cooking step, the beans were soaked in solutions of acid (2.6 and 5.3) or basic (8.4) pH. Chemical and biological methods were used to determine nutritional parameters in growing rats, and the fiber content of the beans was established. As the pH of the soaking solution increased, so did mineral absorption and the apparent digestibility coefficient, which reached suitable values for growing rats, due to the reduced losses of soluble minerals and the increased food intake. Metabolic utilization also improved with increased pH of the soaking solution, although the values were, in general, low as a result of urinary losses under the experimental conditions. For the experimental period of 10 days, the femur and the muscle seem to be good metabolic indicators for calcium, but not for phosphorus or magnesium. The increased amount of cellulose in the soaked seed did not have a negative effect on the digestive utilization of minerals.  相似文献   

16.
Dissolved organic matter is important in translocation and export of nutrients from forest ecosystems. Its mobility in soil is restricted by sorption to mineral surfaces which depends on its chemical properties. Carboxyl and hydroxyl groups form strong bondings to mineral surfaces, whereas the role of N‐containing functional groups in the sorption process is less well understood. We examined in laboratory experiments the binding of dissolved organic matter from the forest floor to amorphous Al(OH)3, goethite, kaolinite, and illite and to subsoils in order to compare the sorption and desorption of dissolved organic C with that of dissolved organic N. The mineral samples were equilibrated with acidic solutions of organic matter at pH 4. In the equilibrium solutions organic C and N and their contribution to two operationally defined fractions, namely the so‐called hydrophilic and hydrophobic fractions, were determined. We measured neutral and acidic amino sugars to discover the nature of the binding of organic N. Within the hydrophilic and hydrophobic fractions, the sorption and desorption of organic C and N did not differ, indicating that there was no preferential binding of N‐containing compounds. The hydrophilic fraction contained more N and sorbed less than the hydrophobic fraction, and so the overall retention of organic N by the mineral phases and subsoils was smaller than that of organic C. Among the amino sugar compounds, muramic acid was preferentially removed from the solution, whereas the neutral amino sugars were sorbed similar to organic C. The results suggest that the sorption of N‐containing compounds is favoured by acidic groups and not by amino groups.  相似文献   

17.
In agricultural systems with low S inputs, soil organic matter is a major source of S and the transformations between organic and inorganic S pools are important for the supply of S to plants. This study was conducted to determine the effect of S fertilizer on the size and activity of organic S pools. For 5 years S fertilizer with a known composition of stable S isotopes was applied to a rotation on a loamy soil and a coarse sandy soil at rates higher than the plant demand. Total organic S in soil organic matter was not affected by sulphur application, but a small increase occurred in the sulphate ester fractions (P<0.05). Inorganic sulphate concentrations in the soil reflected the S application in the year of sampling, whereas S applied in earlier years was not recognized. Organic matter below the plough layer in both soils was enriched with S, possibly as a result or organic matter leaching or an increased clay content in the subsoils. At 0–20 cm, the C:S ratio in organic matter was ca. 100 for both soils, decreasing to 73 and 46 at 60–80 cm for the coarse sandy soil and the loamy soils, respectively. In both soils, isotope data showed that ca. 30% of organic-bonded S at 0–20 cm originated from fertilizer S applied during the last 5 years, irrespective of the S application rate. At 20–40 cm the rate of incorporations was lower and at 40–60 cm no incorporation of fertilizer S into organic matter was recognized. The fertilizer application did not induce net changes in the total organic S fraction, but isotope data indicated that a considerable part of the organic S pool was involved in S cycling in the field.  相似文献   

18.
The quality of mulberry leaf supports good growth and development of silkworm larvae. Mulberry leaves are hampered by the various detrimental diseases and pests. The mealy bug is one of the important insect pests of mulberry; its sap sucking nature may alter nutritive levels. An attempt was made to evaluate the macro and micro nutritive elemental levels in the infested leaves. There was a large variation of nitrogen, phosphorus, potassium, magnesium, manganese and molybdenum in almost all the varieties. There was a small difference in calcium, sulphur, iron, copper, boron and chloride. However, there was no change in zinc content in all the varieties of infested leaves. Disparity shown in majority of the macro nutrients in almost all the mulberry cultivars leads to variation in their quality. This feature of the leaves may hinder the good growth and development of silkworm, in turns producing low quality and poor yield of silk.  相似文献   

19.
Given their organic matter (OM) depletion, agricultural soils can act as carbon (C) sinks if adequate management practices are implemented. OM stabilisation in highly OM‐depleted agricultural soils may depend upon the allocation of OM inputs among particle size fractions that differ in their capacity to stabilise OM. In a set of vegetable garden fields, we determined the magnitude of the differences in soil C and N content between organically and conventionally managed fields and the incorporation of the increased C and N pools to the fine fractions as an indication of the stability of the soil OM accrual. It was carried out in a stockless scenario in which exogenous OM was only used in organically managed fields for the last 20 years (as opposed to conventional management only using mineral fertilisers). Organic fertilisation caused a notable increase in soil organic C and N stocks compared with mineral‐fertilised soils. Such increase remained significant below the plough depth. C and N content increased at all fractions, but the relative contribution of the fine‐silt‐plus‐clay fraction to total C and N decreased at all depths. We concluded that organic management increases soil OM storage, but overall, the stability of the increased OM stocks decreases slightly. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

20.
Isotopic fractionation of dissolved organic carbon percolating through the soil is often interpreted as due to microbial transformation. We investigated the potential effects of sorption on the δ13C of dissolved organic C in field and laboratory experiments. We sampled the organic C in soil water at two forested sites and measured sorption with intact mineral soil and individual minerals (dolomite, ferrihydrite, goethite, and quartz). The dissolved organic C was separated into hydrophilic and hydrophobic fractions using a resin approach. The δ13C values of bulk soils, alkaline‐extractable organic C, and dissolved organic C and its fractions were measured. Hydrophilic and hydrophobic fractions in forest floor seepage water were characterized by 13C‐NMR spectroscopy. At both sites, δ13C of dissolved organic C increased with increasing depth, suggesting that decomposition contributes to the loss of the dissolved organic C. However, there was an enrichment of hydrophilic organic C in the soil solution as the water moved down the soil. The δ13C values of hydrophilic fractions were less negative than those of hydrophobic fractions. The smaller δ13C in the hydrophobic fraction was due to the large contribution of compounds derived from lignin that are depleted in 13C. As the isotope composition of both fractions of dissolved organic C did not change throughout the profile, changes in δ13C of total organic C reflected changes in the relative proportions of its hydrophilic and hydrophobic fractions. The sorption experiments with minerals and soil cores gave similar results. When dissolved organic C came into contact with mineral material, the δ13C of that remaining in solution increased due to preferential sorption of the 13C‐depleted hydrophobic fractions. Moreover, the soils released hydrophilic organic C with large δ13C values, increasing the δ13C of organic C in effluents from soil compared with that in the inflow. Thus, selective sorption of organic C fractions changes δ13C in a way that mimics metabolic transformation and decomposition.  相似文献   

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