首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
A range of 8–25% of fed cinnamic 2-[14C] acid and 9–14% of injected vanillin 5-[14C] were oxidised to 14CO2 at 15 C over 7 and 6 days respectively in an isopod, Oiuscus asellus; a millipede, Pseudopolydesmus serratus; a slug, Deroceras reticulatum; a snail, Oxychilus draparnaldi; and an earthworm, Eisenia foetida. Approximately 2–10% of nonmetabolised and 13–48%, of metabolised vanillin were present in the animal tissues after 6 days. Correspondingly. 1–4% and 22–66% of these materials were found in egesta.A millipede (Oxidus gracilis), O. asellus. D. reticuluttum. O. draparnaldi, and E. foetida were found unable to degrade ring [14C]-, methoxy [14C]- and side chain [14C]-lignin to 14CO2 over 10 days, thus providing very strong evidence that these invertebrates are incapable of degrading liginin.  相似文献   

2.
The termite Nasutitermes exitiosus (Hill) was fed natural and synthetic [14C]labelled lignins and related compounds, and the respired CO2 collected. All the compounds were partially degraded to CO2, from an average of 7% of the added 14C for ring-labelled phenate to 63% for methoxyl-labelled maize lignin and 64% for ring-labelled ferulic acid, during periods of 6–69 days. The breakdown commenced immediately and was linear until the food was consumed. Thereafter a slow release continued for some time. Termite bodies assayed at the end of the experiments contained only a small proportion of the added radioactivity. When live termites were separated from their faeces, it became apparent that most of the decomposition of lignin had taken place in the termites and not externally in the voided faeces. An estimate of respiration rates of N. exitiosus indicates a significant release of C as respired CO2, and this species of termite would appear to return a considerable proportion of the C in litter lignin directly to the atmosphere.  相似文献   

3.
The rate of respiration of radioactive CO2 from fasting Oniscus asellus L. during 7.5 days was qualitatively similar for ring-labeled and carboxyl-labeled benzoic acid. The rate of respiration of ring-labeled benzoic acid during 7 days was quantitatively similar for isopods that were fed throughout, and had received 0.09 μg benzoic 1-14C acid with or without a “load” of 30 μg of unlabeled benzoic acid. The “loaded” animals displayed a qualitative difference in respiring greater quantities of CO2 at night vs day.At 15°C in July, 24.4 per cent of the radioactivity from an injected dose of benzoic l-14C acid was respired over a 7 day period; 1.3 per cent was excreted; 1.9 per cent was present as carbonates; 5.4 per cent was ether-extractable, of which 48 per cent was chromatographically accountable as benzoic acid; and 56.7 per cent of the label was retained in the body.Ring-labeled carbon from benzoic acid was incorporated into the tissues of the isopod. An analysis of a hydrolyzate from the soluble cellular fraction showed at least six identifiable amino acids and four unidentifiable components.  相似文献   

4.
Increased atmospheric CO2 can affect plant growth, so competition among plants may be influenced. Allelopathy is one mechanism involved in plant competition. Experiments were conducted in a controlled-environment chamber to determine if the concentration of atmospheric CO2 altered the dose-response relationship between an allelopathic phenolic acid and tomato seedling biomass. Seeds of Lycopersicon lycopersicum were planted in quartz sand in styrofoam cups and allowed to germinate and grow for 15–17 days. During the next 14 days, seedlings were watered twice daily with nutrient solution amended with p-coumaric acid (4-hydroxycinnamic acid, HOC6H4CH = CHCO2H; ranging 0–0.85 mg mL-1; 5 concentrations in each experiment) and exposed 24 hr day-1 in continuous-stirred tank reactors (CSTRs) to ambient air (335–375 ppm CO2) or ambient air to which 350 ppm CO2 was added (i.e., approximately twice-ambient CO2; two CSTRs per CO2 concentration in each experiment). Dose-response data relating p-coumaric acid concentration and shoot, root, and total biomass were fit to a flexible decay function. In all three experiments, twice-ambient CO2 significantly increased the y-intercept for the dose-response model for the p-coumaric acid effect on shoot biomass by 25–50% but had negligible effects on other aspects of the models. Results suggest that if CO2 affects plant competition, mechanisms involving allelopathic phenolic acids may not be involved.  相似文献   

5.
The fumigation technique for the estimation of microbial biomass-C was applied at different periods after amendment of three agricultural soils with 14C-labelled glucose, cellulose and wheat roots. By daily monitoring of evolved CO2 and 14CO2 it was recognized that the CO2 from the degradation of the amendment had an interfering effect on biomass calculations. Biomass estimations were valid only when CO2 from the degradation of the amendment had slowed, 3 days after glucose amendment, 14 days after addition of cellulose, and 28 days after amendment with wheat roots.Fumigated, reinoculated soils degraded glucose faster than did the corresponding control samples, causing an overestimation of biomass-C. By contrast biomass-C was underestimated in soils amended with cellulose or wheat roots due to lower rates of degradation of the added C-sources in fumigated samples. The reduced capacity for degradation of complex organic materials may be due to smaller decomposer populations in inoculated fumigated soils; populations recovered within 20 days to only 10–20% of their original biomass-C content. Re-establishment of biomass in fumigated samples was tested with inocula in amounts increasing to 10, 50 and 100% of corresponding control samples. The K-factor was not influenced by these treatments. Estimates of biomass in soil during the rapid phase of degradation of wheat roots were influenced by the amount of inoculum.  相似文献   

6.
Wheat plants were grown on two soils of different texture, a sandy soil and a silty clay loam, in an atmosphere containing 14CO2. The 14C and total C content of the shoots, roots, soil rhizosphere CO2 and soil microbial biomass were measured 21, 28, 35 and 42 days after germination. There was a pronounced effect of soil texture on the turnover of root-derived C through the microbial biomass. Turnover was relatively fast and at a constant rate in the sandy soil but slowed down in the clay soil, following an initial high assimilation of root products into the microbial biomass.Four percent of the total fixed 14C was retained in the clay loam after 6 weeks compared with a corresponding value of 1.2% for the sandy soil. The proportion of fixed 14C recovered as rhizosphere CO2 at each of the sampling times was relatively constant for the sandy soil (ca 19%) but decreased from 17% at day 28 to 11% at day 42 in the clay soil. The proportion of total fixed 14C in the soil biomass as measured by a fumigation technique increased to a maximum value of 20% after 6 weeks in the sandy soil but decreased in the clay soil from 86% at day 21 to 26% after 42 days plant growth.  相似文献   

7.
During 1 yr, CO2-C losses from 7 agricultural soils containing 0.5–1.5% organic C ranged from 70 to 243 mg 100 g ? 1 while losses from three allophanic soils containing 4.9–8.9% organic C varied from 92 to 191 mg. Losses as 14CO2 from ring-labeled model and cornstalk lignins averaged about 30% from the agricultural soils compared to about 11% for the allophanic soils. Losses of 2-side chain lignin carbons were about the same as for the ring carbons. Carbon losses from 1-side chain and methoxyl C varied from 42 to 59% in the normal soils while losses from the allophanic soils were a third to a half these values. From 6 to 9% of protein, cysteine, lysine, and glucosamine carbons linked into model humic acid polymers were lost during 1 yr in the allophanic soils compared with 13–24% from the normal soils. Comparable losses from two fungal melanins were 7–15% for the normal soils and 2–4% for the allophanic soils.  相似文献   

8.
Five microbial species (Aspergillus flavus, Trichoderma viride, Streptomyces sp., Arthrobacter sp., Achromobacter liquefaciens) were cultivated in liquid media containing 14C-labelled glucose. The decomposition of these microorganisms was recorded in four different soils after chloroform fumigation by a technique related to that proposed by Jenkinson and Powlson, to determine the mineralization rate of microbial organic matter (Kc coefficient). Three treatments were used: untreated soil, fumigated soil alone and fumigated soil supplied with 14C-labelled cells. Total evolved CO2 and 14CO2 were measured after 7 and 14 days at 28°C.The labelled microorganisms enabled the calculation of mineralization rate Kc (Kc = mineralized microbial carbon/supplied microbial carbon). The extent of mineralization of labelled microbial carbon depended on the type of soil and on the microbial species. Statistical analysis of results at 7 days showed that 58% of the variance is taken in account by the soil effect and 32% by the microorganism effect. Between 35 and 49% of the supplied microbial C was mineralized in 7 days according to the soil type and the species of microorganism. Our results confirmed that the average value for Kc = 0.41 is acceptable, but Kc variability according to soil type must be considered.The priming effect on organic C and native microbial biomass mineralization, due to microbial carbon addition was obtained by comparison between the amount of non-labelled CO2-C produced by fumigated soils with or without added labelled microorganisms: this priming effect was generally negligible.These results indicate that the major portion of the error of microbial biomass measurement comes from the Kc estimation.  相似文献   

9.
The effect of endogeic earthworms (Octolasion tyrtaeum) and the availability of clay (Montmorillonite) on the mobilization and stabilization of uniformly 14C-labelled catechol mixed into arable and forest soil was investigated in a short- and a long-term microcosm experiment. By using arable and forest soil the effect of earthworms and clay in soils differing in the saturation of the mineral matrix with organic matter was investigated. In the short-term experiment microcosms were destructively sampled when the soil had been transformed into casts. In the long-term experiment earthworm casts produced during 7 days and non-processed soil were incubated for three further months. Production of CO2 and 14CO2 were measured at regular intervals. Accumulation of 14C in humic fractions (DOM, fulvic acids, humic acids and humin) of the casts and the non-processed soil and incorporation of 14C into earthworm tissue were determined.Incorporation of 14C into earthworm tissue was low, with 0.1 and 0.44% recovered in the short- and long-term experiment, respectively, suggesting that endogeic earthworms preferentially assimilate non-phenolic soil carbon. Cumulative production of CO2-C was significantly increased in casts produced from the arable soil, but lower in casts produced from the forest soil; generally, the production of CO2-C was higher in forest than in arable soil. Both soils differed in the pattern of 14CO2-C production; initially it was higher in the forest soil than in the arable soil, whereas later the opposite was true. Octolasion tyrtaeum did not affect 14CO2-C production in the forest soil, but increased it in the arable soil early in the experiment; clay counteracted this effect. Clay and O. tyrtaeum did not affect integration of 14C into humic fractions of the forest soil. In contrast, in the arable soil O. tyrtaeum increased the amount of 14C in the labile fractions, whereas clay increased it in the humin fraction.The results indicate that endogeic earthworms increase microbial activity and thus mineralization of phenolic compounds, whereas clay decreases it presumably by binding phenolic compounds to clay particles when passing through the earthworm gut. Endogeic earthworms and clay are only of minor importance for the fate of catechol in soils with high organic matter, clay and microbial biomass concentrations, but in contrast affect the fate of phenolic compounds in low clay soils.  相似文献   

10.
Photosynthesis of higher plants drives carbon (C) allocation below-ground and controls the supply of assimilates to roots and to rhizosphere microorganisms. To investigate the effect of limited photosynthesis on C allocation, redistribution and reutilization in plant and soil microorganisms, perennial grass Lolium perenne and legume Medicago sativa were clipped or shaded. Plants were labelled with three 14C pulses to trace allocation and reutilization of C assimilated before clipping or shading. Five days after the last 14C pulse, plants were clipped or shaded and the total CO2 and 14CO2 efflux from the soil was measured. 14C in above- and below-ground plant biomass and bulk soil, rhizosphere soil and microorganisms was determined 10 days after clipping or shading.After clipping, 2% of the total assimilated 14C originating mainly from root reserves were detected in the newly grown shoots. This corresponded to a translocation of 5 and 8% of total 14C from reserve organs to new shoots of L. perenne and M. sativa, respectively. The total CO2 efflux from soil decreased after shading of both plant species, whereas after clipping, this was only true for L. perenne. The 14CO2 efflux from soil did not change after clipping of both species. An increased 14CO2 efflux from soil under shading for both plants indicated that lower assimilation was compensated by higher utilization of the reserve C for root and rhizomicrobial respiration.We conclude that C stored in roots is an important factor for plant recovery after limiting photosynthesis. This stored C is important for shoot regrowth after clipping, whereas after shading, it is utilized mainly for maintenance of root respiration. Based on these results as well as on a review of several studies on C reutilization for regrowth after clipping, we conclude that because of the high energy demand for nitrogen fixation, legumes use a higher portion (9–10%) of stored C for regrowth compared to grasses (5–7%). The effects of limited photosynthesis were of minor importance for the exudation of the reserve C and thus, have no effect on the uptake of this C by microorganisms.  相似文献   

11.
A fungus, Fusarium solani, isolated from the soil, degraded ioxynil (3,5-diiodo-4-hydroxyben-zonitrile) in pure culture into at least eight products. Five products were detected in the organic fractions extracted from a culture grown in [14C]cyano-labeled ioxynil. Three additional products were separated by ion-exchange chromatography of the acidified aqueous phase. Cultures grown in the presence of [14C]ring-labeled ioxynil produced the same products in the organic extract and four to five products in the aqueous phase. The cyano-carbon of ioxynil was released as CO2 at a faster rate than that of ring-carbons and was released after the initial ring cleavage. Two of the metabolites were identified as 3,5-diiodo-4-hydroxybenzamide and 3,5-diiodo-4-hydroxybenzoic acid.  相似文献   

12.
Arable soil containing 10 ppm of dieldrin-14C uniformly labelled in its chlorinated ring released 0·30 and 1.86 per cent of the activity as 14CO2 from sterile and non-sterile samples respectively during 7 weeks incubation. In a second experiment with percolated or aerated soil samples containing 50 ppm dieldrin-14C with or without glucose about 0·30 per cent was lost as 14CO2. The different experimental conditions only influenced the time pattern of 14CO2 evolution. About half of 177 bacterial strains isolated from the same soil produced water-soluble dieldrin metabolites in culture. From 14 selected strains the three most active strains (Nocardia, Corynebacterium and aMicrococcus sp.) were incubated for 5 weeks with 0·4 ppm dieldrin-14C and released 0·06–0·11 per cent recoverable as BaCO3 in aerated culture and 0·14–0·2 per cent in stationary culture.  相似文献   

13.
Rising levels of atmospheric CO2 have often been found to increase above and belowground biomass production of C3 plants. The additional translocation of organic matter into soils by increased root mass and exudates are supposed to possibly increase C pools in terrestrial ecosystems. Corresponding investigations were mostly conducted under more or less artificial indoor conditions with disturbed soils. To overcome these limitations, we conducted a 14CO2 pulse-labelling experiment within the German FACE project to elucidate the role of an arable crop system in carbon sequestration under elevated CO2. We cultivated spring wheat cv. “Minaret” with usual fertilisation and ample water supply in stainless steel cylinders forced into the soil of a control and a FACE plot. Between stem elongation and beginning of ripening the plants were repeatedly pulse-labelled with 14CO2 in the field. Soil born total CO2 and 14CO2 was monitored daily till harvest. Thereafter, the distribution of 14C was analysed in all plant parts, soil, soil mineral fractions and soil microbial biomass. Due to the small number of grown wheat plants (40) in each ring and the inherent low statistical power, no significant above and belowground growth effect of elevated CO2 was detected at harvest. But in comparison to ambient conditions, 28% more 14CO2 and 12% more total CO2 was evolved from soil under elevated CO2 (550 μmol CO2 mol−1). In the root-free soil 27% more residual 14C was found in the FACE soil than in the soil from the ambient ring. In soil samples from both treatments about 80% of residual 14C was found in the clay fraction and 7% in the silt fraction. Very low 14C contents in the CFE extracts of microbial biomass in the soil from both CO2 treatments did not allow assessing their influence on this parameter. Since the calculated specific radioactivity of soil born 14CO2 gave no indication of an accelerated priming effect in the FACE soil, we conclude that wheat plants grown under elevated CO2 can contribute to an additional net carbon gain in soils.  相似文献   

14.
利用开放式空气CO2浓度升高(Free Air Carbon-dioxide Enrichment, FACE)平台, 研究了低氮(LN)和常氮(NN)水平下, 大气CO2浓度升高对冬小麦叶片酚酸类物质代谢的影响.结果表明, CO2浓度升高对小麦叶片水杨酸、对羟基苯甲酸、肉桂酸、阿魏酸和香草酸含量的影响随供氮水平的不同而有所差异.低氮下小麦通过提高叶片苯丙氨酸解氨酶(PAL)活性(30.1%)而使其含量均显著增加, 增幅分别达33.7%、119.6%、26.7%、39.9%和28.6%; 而常氮下PAL活性和酚酸类含量变化均未达显著水平.可见, 大气CO2浓度升高对冬小麦酚酸类物质代谢的影响受氮水平的调控, 在未来CO2浓度升高条件下, 选择适宜的施肥水平将显得更为重要.此外, 总酚含量与水杨酸、对羟基苯甲酸、肉桂酸、阿魏酸和香草酸等含量变化趋势基本一致, 且总酚含量变化的79.6%～151.4%是由这几种酚酸含量变化引起的, 说明CO2浓度升高使水杨酸、对羟基苯甲酸、肉桂酸、阿魏酸和香草酸等含量增加是总酚含量增加的直接原因.低氮条件下大气CO2浓度升高将通过改变酚酸类物质代谢而间接影响小麦与伴生杂草的关系.  相似文献   

15.
The 14C‐labeled substrates glucose, fructose, alanine, glycine, oxalic acid, acetic acid, and catechol were incubated at 20 °C in a model system that consisted of sand mixed with lignin or peat (3 % Corg). Each substrate was added at either 80 or 400 μg C (g sand)—1. During 26 days of incubation with an inoculum extracted from forest soil, the amount of CO2 evolved was measured hourly. The amount of 14CO2 was determined after 4, 6, 12, 19, and 26 days. After 26 days of incubation, each substrate showed priming effects, but not in all examined treatments. Most substrates stimulated the degradation of the model substances (positive priming effects). Negative priming effects only were found in the lignin system with oxalic acid and catechol addition at both concentrations. The strongest positive priming occurred in the peat system with the oxalic acid addition of 80 μg C g—1 where 1.8 % of the peat were mineralized after 26 days, compared to 0.7 % in the control. The addition of 400 μg alanine‐C g—1 caused the strongest increase in lignin mineralization, amounting to 3.9 % compared to 2.8 % in the control. During the incubation the extent of priming changed with time. Most substrates caused the strongest effects during the first 4 to 10 days of incubation. The extent of priming depended on substrate type, substrate concentration, and organic model substance. Possibly this is due to the activation of different microorganisms.  相似文献   

16.
Labelled 14C-acetate and 15N-(NH4)2SO4 were added to a clay soil in the laboratory to follow transformations of microbial C and N, A fungal population developed initially, reaching a maximum by day 5, then rapidly declined and was replaced by a population dominated by bacteria and actinomycetes. Soil samples containing doubly-labelled microorganisms and their metabolites were extracted by Na4P2O7, and the extracted material further separated with phenol.The highly labelled acid-soluble (fulvic acid) fraction of the Na4P2O7 extract contained extracellular metabolites of low molecular weight which were rapidly attacked and converted to new microbial biomass, metabolites, mineral N or CO2. Na4P2O7 also removed an acid-insoluble (humic acid) fraction of which up to 70 per cent of the labelled C and N could be removed by phenol. Attack of these recently synthesized extracellular materials was indicated by a rapid decline of Na4P2O7 extractable C and N during the growth of bacteria and actinomycetes.Following Na4P2O7 extraction, the residue was sonicated and peptized in water and the components of the microbial biomass were partitioned into sedimentation fractions by centrifugation. The components concentrated in the > 0.2 μm fraction, which were hypothesized as being cell wall components, were more resistant to attack than materials in the < 0.04 μm fraction. The materials in the latter fraction were thought to originate from cytoplasmic constituents. The labelled materials in the < 0.04 μm sized fraction, which accumulated as the fungal population developed, were utilized less rapidly by the developing bacterial population.Decomposition of the microbial population resulted in transfer of C and N through various sediment fractions. The organic fraction (considered to be cytoplasmic material and adsorbed extracellular metabolites) which became labelled as the bacterial population developed, was utilized less rapidly by the developing bacterial population than components removable by Na4P2O7. Evolution of 14CO2, production of microbial material and immobilization of N closely paralleled the incorporation and release of these elements from the fractions. The similarity of the behavior patterns of these elements suggested they were intimately associated within the soil microbial system studied. This demonstrated that N transformations were highly dependent on C transformations.  相似文献   

17.
14C, supplied continuously to plant tops as 14CO2, was recovered in water-soluble organic material when pots with wheat, clover or ryegrass growing in a podzolic sand were leached with distilled water at weekly intervals. Leachates and root-free soil contained, respectively, 0·15–0·3 and 2·7–5·4% of the total 14C activity recovered after 8 weeks growth. Plant derived C represented 0·8–1·3% of the total organic C in root-free soils.Water-soluble organic C decreased in successive leachings to reach a steady value, approximately 20 μgC/ml for all treatments. Labelled C represented 14·4–19·5% of this value. Total organic C recovered in the leachates accounted for ca. 0·5% of the soil C, for all treatments. Approximately 15% of the labelled material in the final leachates behaved as neutral sugar, the remainder occurring in a charged complex. A membrane filter (M.Wt. cut-off ~ 103) retained >60% of the radioactivity.  相似文献   

18.
When phosphatidyl [N-methyl-14CO]choline or phosphatidyl choline di[l-14C]palmitoyl were incubated in a low phosphorus status soil there was an early and rapid release of CO2 and a concurrent increase in NaHCO3-extractable inorganic phosphorus, indicating mineralization of the added organic phosphorus. Mineraiization slowed dramatically and by 20 days only 50% of the carbon from the molecule was accounted for as microbial biomass or respiration. The rates of release of 14CO2 from the two labelled substrates indicated that 14CO2 measured as respiration initially arose more swiftly from the carbon portion of the molecules with easiest access to enzymic degradation.  相似文献   

19.
Plant response to increasing atmospheric CO2 partial pressure (pCO2) depends on several factors, one of which is mineral nitrogen availability facilitated by the mineralisation of organic N. Gross rates of N mineralisation were examined in grassland soils exposed to ambient (36 Pa) and elevated (60 Pa) atmospheric pCO2 for 7 years in the Swiss Free Air Carbon dioxide Enrichment experiment. It was hypothesized that increased below-ground translocation of photoassimilates at elevated pCO2 would lead to an increase in immobilisation of N due to an excess supply of energy to the roots and rhizosphere. Intact soil cores were sampled from Lolium perenne and Trifolium repens swards in May and September, 2000. The rates of gross N mineralisation (m) and NH4+ consumption (c) were determined using 15N isotopic dilution during a 51-h period of incubation. The rates of N immobilisation were estimated either as the difference between m and the net N mineralisation rate or as the amount of 15N released from the microbial biomass after chloroform fumigation. Soil samples from both swards showed that the rates of gross N mineralisation and NH4+ consumption did not change significantly under elevated pCO2. The lack of a significant effect of elevated pCO2 on organic N turnover was consistent with the similar size of the microbial biomass and similar immobilisation of applied 15N in the microbial N pool under ambient and elevated pCO2. Rates of m and c, and microbial 15N did not differ significantly between the two sward types although a weak (p<0.1) pCO2 by sward interaction occurred. A significantly larger amount of NO3− was recovered at the end of the incubation in soil taken from T. repens swards compared to that from L. perenne swards. Eleven percent of the added 15N were recovered in the roots in the cores sampled under L. perenne, while only 5% were recovered in roots of T. repens. These results demonstrate that roots remained a considerable sink despite the shoots being cut at ground level prior to incubation and suggest that the calculation of N immobilisation from gross and net rates of mineralisation in soils with a high root biomass does not reflect the actual immobilisation of N in the microbial biomass. The results of this study did not support the initial hypothesis and indicate that below-ground turnover of N, as well as N availability, measured in short-term experiments are not strongly affected by long-term exposure to elevated pCO2. It is suggested that differences in plant N demand, rather than major changes in soil N mineralisation/immobilisation, are the long-term driving factors for N dynamics in these grassland systems.  相似文献   

20.
Wheat plants were grown in an atmosphere containing 14CO2 at temperatures of 10°C or 18°C for periods from 3–8 weeks. The plant roots were maintained under sterile or non-sterile conditions in soil contained in sealed pots which were flushed to displace respired 14CO2. The 14C content of the shoots, roots and soil was measured at harvest. The loss of 14C from the roots, expressed either in terms of total 14C recovered from the pots or 14C translocated to the roots, ranged from 14.3–22.6%, mean 17.3% or 29.2–44.4%, mean 39.2%, respectively. The presence of soil microorganisms significantly increased 14CO2 release from the rhizosphere but had no effect on the 14C content of the soil. Fractionation of 6 m HC1 hydrolysates from sterile and non-sterile soils showed the presence in all soils of material behaving as neutral sugars and amino acids, in quantities representing 5.9–9.2% and 13.4–17.2% of the soil 14C content for the sugar and amino acid fractions respectively. It is proposed that a major loss of root carbon resulted from autolysis of the root cortex. Root lysis was increased by soil microorganisms, apparently without penetration of the plant cell walls.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号