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1.
Lichen phenolics that are known to leach out from lichen thalli during rainfall episodes are considered to be allelopathic or antimicrobial agents. On the other hand, small organic molecules originating from aboveground vegetation generally constitute an important C source for the soil microbial community. We studied the effects of leaching lichen acids on soil microbial processes by chemically removing usnic (UA) and perlatolic acid (PA) from the extracellular space of mat-forming lichen, Cladina stellaris, a dominant component of the ground vegetation in boreal oligotrophic forests. Removal of UA and PA did not affect the intracellular contents of the lichen. We hypothesized that if lichen acids have an adverse effect on soil biota, microbial respiration would increase underneath chemically manipulated lichen mats. In turn, if these substances provide energy source for the microorganisms, microbial respiration would decline under lichens from which PA and UA has been removed. Microbial metabolic activity, qCO2 was significantly lower under the lichens from which UA and PA had been removed, thus supporting the latter hypothesis. Removing UA and PA did not affect the amount of microbial C, N and P, or soil nutrient concentrations. Our results suggest that the microbial community in the soil under a lichen carpet is adapted to the presence of these lichen secondary metabolites and can utilize them as a C source. The approach of removing lichen substances from the system could be used as an effective research tool as it can overcome several problems that are often common in the studies on allelopathic interactions. 相似文献
2.
The role of the lichens in the breakdown of some tuscan rocks In the natural tuscan environment the rocks breakdown by means of the lichens results in the dissolution of primary minerals and not in the formation of neogenesis minerals. Large amounts of Ca-oxalate were found in the weathered sheets of calcareous rocks, while in the ferromagnesian ones the soluble iron oxalate is easily washed away, thus facilitating further weathering. In the lichen sheets the Fe++: Fe+++ ratio is almost constant in contrast with the values found in the rock. 相似文献
3.
采用随机区组和裂区设计,通过盆栽和根箱模拟试验研究了石灰性土壤,在水分充足的条件下施磷及磷、铁对柠条生长发育及根际土壤养分有效性的影响。盆栽试验结果表明,柠条的生物产量随着施磷水平的增加而增加;在低磷或磷胁迫条件下,柠条的地上部生长受到抑制,根冠比增大,土壤pH值迅速降低。根箱模拟试验发现,不同的铁、磷施肥配比对柠条生物产量的影响不同,当磷和铁的施用量分别为P2O50.15 g kg-1 和FeSO4·7H2O0.03g kg-1时能明显提高柠条的生物量。不同铁、磷配比对柠条根际土壤有效磷含量影响的根际范围是0-6 mm之间,在此范围内供试土壤有效磷含量随距离快速下降,并与根际土壤pH值呈反比。柠条对根际土壤pH的调控主要受磷水平的影响,而施铁水平对根际和根外土壤pH值的影响比较小。 相似文献
4.
Phosphate sorption was studied in samples (0 - 20 cm depth) of five soils from Egypt (pH 7.4 - 8.7), four soils from Ethiopia (pH 3.9 - 5.3) and six soils from Germany (pH 3.3 - 7.2). Sorption parameters were calculated according to Pagel and Van Huay (1976) and according to Langmuir (Syers et al., 1973). Phosphate sorption parameters and oxalate extractable Fe and Al (Feox, Alox) were related to the phosphate uptake by young rye plants in Neubauer pot experiments. P sorption parameter after Pagel and Van Huay (A) correlated significantly positively with the Feox and Alox content in acid (r = 0.73) as well as in calcareous soils (r = 0.89) if the whole equilibrium concentration range (0 - 14 mg P/L) was considered. The relations calculated after Langmuir (B) were similar. P uptake by rye in acid soils was negatively correlated with the affinity constant n (r = ?0.76, (A)). In calcareous soils, a negative correlation between P uptake and affinity constant was calculated in the lower P equilibrium range (0 - 2.8 mg P/L) only for (B). Thus, P uptake decreased with increasing strength of P bonding to soil. From these results it is concluded that phosphate sorbed to Fe/Al oxides is an important P source for plants in acid and calcareous soils. 相似文献
5.
William J. Zimmerman 《Biology and Fertility of Soils》1992,13(3):192-194
Summary The processes of NH
4
+
uptake and induced NH
4
+
excretion in the Azolla-Anabaena symbiosis were studied. Uptake rates in accessions of Azolla microphylla and A. mexicana were similar. No pH optimum for NH
4
+
uptake was observed. Rates of N excretion induced by methionine sulfoximine were also similar. When A. caroliniana was subjected to the herbicide Ignite (Hoechst-Roussel), more NH
4
+
was initially released than with methionine sulfoximine treatment. Glutamine synthetase was not completely suppressed. 相似文献
6.
In our previous studies, pigeonpea (Cajanus cajan L.), groundnut (Arachis hypogaea L.), and rice (Oryza sativa L.) were found to have a higher ability to take up Fe- or Al-bound phosphorus (P) than soybean (Glycine max L.) and sorghum (Sorghum bicolor L.). Phosphorus absorption characteristics like I max, K m, C min, and FeIII reduction activity of roots, and root exudates in various crops were examined with a view to analyzing the mechanisms of P uptake. Phosphorus uptake ability was largely unrelated to variations in I max, K m, C min, and FeIII reduction activity of roots. Phosphorus-solubilizing activity in anionic fractions of root exudates was detected in pigeonpea but not in rice or groundnut. Malonic acid was the major component followed by oxalic and piscidic acid. These organic acids were able to release P from FePO4 and A1PO4. The higher P uptake ability of pigeonpea in soils with low P fertility presumably depends on the secretion of such organic acids from roots. 相似文献
7.
In this batch type parametric study the influence of phosphate concentrations on the extent of its removal by constant amount of FeCl3 at different pH, temperature and aging time is evaluated. The efficiency of FeCl3 in removing the phosphate is strongly dependent on the pH of the precipitation. At P/Fe molar ratios of higher than 0.5 the pH of maximum phosphate removal is found to be at pH 2.5 and is followed by pH 4, 6 and 9. The optimum pH for maximal phosphate removal greatly varies with the amount of phosphate present relative to that of iron present. It is also observed that maximal phosphate removal by FeCl3-solution is achieved at P/Fe ratios of more than 1, 0 suggesting that in removal process not only Fe3+ but also colloidal hydroxide particles could play an important role. The samples of non-aged synthesized precipitates obtained at P/Fe ratios of 8, 4 and 2 at pH 2.5 are found to have characteristic lines of strengite. The formation of strengite at room temperature from fresh solutions has not previously been reported. Thermally treated precipitates with the characteristic lines of strengite transform into a quartz-like phase which suggests that the loss of the coordinated water leads to a compound like ABO4 where A and B both are in tetrahedral coordination. Upon heat treatment, the amorphous precipitates, having P/Fe ratios > 0.5, obtained between pH 2.5 and 6 result in a quartzlike phase. However, the characteristic lines of the quartz phase are not of the same intensity. In contrast, the precipitates having P/Fe ratios < 0.5 transform into hematite after heat treatment. The thermally treated products of precipitates obtained at pH 9 are found to have η-Fe2O3 phase which indicates that basic phosphates formed at this pH are structurally similar to that of basic sulfates. 相似文献
8.
《Communications in Soil Science and Plant Analysis》2012,43(1-2):139-158
Abstract Extracting sludge‐amended soil with DTPA does not always give a reliable measure of plant‐available heavy metals. The major purpose of this greenhouse pot study was to help explain why. Two anaerobically digested sludges from sewages treated with either Ca(OH)2or FeCl3were applied to 3‐kg samples of a Mollic Albaqualf previously limed with Ca(OH)2rates of 0, 2.5, and 10g/pot that resulted in pHs in the check pots of 5.4, 6.2, or 7.7 after the first harvest. Sludge rates provided 0, 200, 40, 800, and 1600 mg Zn kg‐1of soil. Two consecutive crops of soybeans (Glycine MaxL.) were grown for 42 d each in the greenhouse. DTPA‐extractable, soil‐solution, and plant concentrations of Cu2+, Ni2+, and Zn2+were measured. Dry matter yields were depressed due to salt toxicity, while DTPA‐extracted Cu2+correlated with plant uptake of Cu2+for both sludges. DTPA‐extracted Ni2+also correlated with plant Ni2+from the Ca(OH)2‐sludge‐amended soil, although DTPA‐extracted Ni2+did not correlate with plant uptake of Ni2+from the FeCl3‐sludge‐amended soil, DTPA‐extracted Zn did not correlate with plant uptake of Zn2+from any sludge‐amended soil. Soil‐solution composition correlated with plant uptake of Cu2+and Ni2+in both sludges; it also correlated with plant uptake of Zn2+from FeCl3‐sludge‐amended soil but not from Ca(OH)2‐sludge‐amended soil. DTPA extraction probably failed with Ni2+and Zn2+because of (i) its ineffectiveness at low pH, (ii) the inability of DTPA to buffer each soil extract near pH 7.3, and (iii) increased amounts of soluble chelated micronutrients at higher sludge rates and higher soil pHs. Soil‐solution composition seemed to fail only where micronutrient cations in solution probably were present largely as organic chelates 相似文献
9.
Abstract Iron‐inefficient TAM 0–312 and Fe‐efficient Coker 227 oats (Strategy II plants) differ in their release of phytosiderophore in response to iron‐deficiency stress—the Fe‐efficient Coker 227 releases a phytosiderophore whereas the Fe‐inefficient TAM 0–312 does not. The phytosiderophore released by Coker 227 oats in response to Fe‐deficiency stress does not appear to transport Fe into the plant as Fe phytosiderophore. When the Fe‐inefficient TAM 0–312 and Fe‐efficient Coker 227 oats were subjected to Fe supplied as Fe2+(BPDS)3, Fe3+HEDTA, as Fe3+EDDHA, Coker 227 utilized the Fe more efficiently than TAM 0–312 in every case. Both cultivars reduced Fe3+ as FeCl3 to form Fe2+(BPOS)3 and responded better to this form of Fe than Fe supplied as the ferric chelate. Reduction of Fe3+ at the root appears to be a factor that facilitates iron uptake by Coker 227 oats and the release of a phytosiderophore appears to make more Fe available at the root that can be reduced and transported to plant tops. 相似文献
10.
Mary M. Peet C. David Raper Jr. Leslie C. Tolley Wayne P. Robarge 《Journal of plant nutrition》2013,36(9):787-798
Tomato (Lycopersicon esculentum L. Mill. ‘Vendor') plants were grown for 21 days in flowing solution culture with N supplied as either 1.0 mM NO3 ‐ or 1.0 mM NH4 +. Acidity in the solutions was automatically maintained at pH 6.0. Accumulation and distribution of dry matter and total N and net photosynthetic rate were not affected by source of N. Thus, when rhizosphere acidity was controlled at pH 6.0 during uptake, either NO3 ‐ or NH4 + can be used efficiently by tomato. Uptake of K+ and Ca2+ were not altered by N source, but uptake of Mg2+ was reduced in NH4 +‐fed plants. This indicates that uptake of Mg2+ was regulated at least partially by ionic balance within the plant. 相似文献
11.
Lichens are prominent components of many biological soil crusts. Owing to their persistence, lichen thalli create microhabitats for other microbes. Here, the structure of bacterial communities at the thallus–soil interface in lichen soil crusts was studied by using fluorescence in situ hybridization (FISH), confocal laser scanning microscopy (CLSM) and 3D image reconstruction. Terricolous lichen thalli above the tree-line in open habitats of the Austrian Alps were sampled. We selected six lichen species associated with green algal photobionts: Arthrorhaphis citrinella, Baeomyces placophyllus, B. rufus, Icmadophila ericetorum, Psora decipiens and Trapeliopsis granulosa. Alphaproteobacteria and Acidobacteria are predominant in these soil crust lichens, where the latter are frequently present in the lower part of lichen thalli and in the hypothallosphere. In the inconspicuous thallus structures of Arthrorhaphis citrinella, Baeomyces rufus, Icmadophila ericetorum and Trapeliopsis granulosa we observed association of bacteria with algal cells in soil particles and on the outer surface of the mycobiont–photobiont aggregates. We found bacterial cells intermixed with photobiont cells in the lower part of the lichen thalli and as small colonies on the surface of the squamules of Baeomyces placophyllus and Psora decipiens. Moreover, technical issues of performing FISH and confocal microscopy with biological soil crusts are discussed. 相似文献
12.
Nutrient uptake by snapdragon (Antirrhinum majus L. ‘Peoria') was compared at five root‐zone temperatures: 8, 15, 22, 29, and 36°C. Uptake of nitrate (NO3 ‐‐N), ammonium (NH4 +‐N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), boron (B), iron (Fe), manganese (Mn), and zinc (Zn) responded quadratically to increasing root‐zone temperature. Greatest nutrient uptake temperature varied with nutrient but ranged from 15 to 29°C. Uptake of copper (Cu) and molybdenum (Mo) were unaffected by root‐zone temperature. Dry weight gain and stem length also responded quadratically to increasing root‐zone temperature. Optimal temperatures for nutrient uptake and growth were similar, averaging 22°C. These results indicate increasing or maintaining root‐zone temperatures near 22°C maximizes growth and nutrient uptake of snapdragons. 相似文献
13.
Uptake of NO3 ‐, NH4 +, P, K++, Ca++ and Mg++, as influenced by the stage of plant development and three NO3 ‐: NH4 + ratios (1: 0, 1: 1, and 0: 1), was determined for sweet pepper (Capsicum annuum L. cv. ‘California Wonder'). Uptake was highest during fruit development and immediately after fruit harvest, indicating that fruit removal promotes nutrient uptake. When NO3 ‐ and NH4 + were supplied in equal concentrations, NO3 ‐ was absorbed more readily. Each increment in NH4 + decreased the uptake of K+, Ca++, and Mg++ by fruit tissue, while no significant effect on the N and P content of the fruit was observed. Ammonium nutrition reduced plant dry weight and fruit yield in comparison to NO3 ‐. Results from this study suggest that NO3 ‐ is the preferred N form, and that fertilizer application should be scheduled according to specific physiological stages to maximize nutrient uptake. Nutrient content of vegetative tissue was not indicative of potential yield. 相似文献
14.
Donald F. Perkins 《Water, air, and soil pollution》1992,64(3-4):503-510
The relationship between F contents and damage to previously unpolluted saxicolous lichens (Ramalina sp) was examined in the vicinity of an Al works on the island of Anglesey, North Wales. Damage was greatest <2 km from the works, where 41% of Ramalina thalli showed >50% chlorosis and necrosis. Loss of lichens (measured by changes in percent cover in 58 permanent quadrats) decreased with increasing distance from the works. Lichens well-exposed to emissions had the largest F content and 20 to 30% more losses than those less-exposed. Well-exposed lichens had rates of loss of cover of 4.9% km?1 yr?1, whereas more sheltered thalli had losses of 3.7% km?1 yr?1. In contrast, relatively uncontaminated lichens increased in % cover. Content of F reflected both distance from the works and exposure to emissions; losses, and F content, were closely related (r2=0.90). Lichens containing 300, 100 and 50 μg F g?1 dry weight lost 46, 15 and 10% of cover yr?1, respectively. 相似文献
15.
Root-induced changes in the rhizosphere may affect mineral nutrition of plants in various ways. Examples for this are changes in rhizosphere pH in response to the source of nitrogen (NH4-N versus NO3-N), and iron and phosphorus deficiency. These pH changes can readily be demonstrated by infiltration of the soil with agar containing a pH indicator. The rhizosphere pH may be as much as 2 units higher or lower than the pH of the bulk soil. Also along the roots distinct differences in rhizosphere pH exist. In response to iron deficiency most plant species in their apical root zones increase the rate of H+ net excretion (acidification), the reducing capacity, the rate of FeIII reduction and iron uptake. Also manganese reduction and uptake is increased several-fold, leading to high manganese concentrations in iron deficient plants. Low-molecular-weight root exudates may enhance mobilization of mineral nutrients in the rhizosphere. In response to iron deficiency, roots of grass species release non-proteinogenic amino acids (?phytosiderophores”?) which dissolve inorganic iron compounds by chelation of FeIII and also mediate the plasma membrane transport of this chelated iron into the roots. A particular mechanism of mobilization of phosphorus in the rhizosphere exists in white lupin (Lupinus albus L.). In this species, phosphorus deficiency induces the formation of so-called proteoid roots. In these root zones sparingly soluble iron and aluminium phosphates are mobilized by the exudation of chelating substances (probably citrate), net excretion of H+ and increase in the reducing capacity. In mixed culture with white lupin, phosphorus uptake per unit root length of wheat (Triticum aestivum L.) plants from a soil low in available P is increased, indicating that wheat can take up phosphorus mobilized in the proteoid root zones of lupin. At the rhizoplane and in the root (root homogenates) of several plant species grown in different soils, of the total number of bacteria less than 1 % are N2-fixing (diazotrophe) bacteria, mainly Enterobacter and Klebsiella. The proportion of the diazotroph bacteria is higher in the rhizosphere soil. This discrimination of diazotroph bacteria in the rhizosphere is increased with foliar application of combined nitrogen. Inoculation with the diazotroph bacteria Azospirillum increases root length and enhances formation of lateral roots and root hairs similarly as does application of auxin (IAA). Thus rhizosphere bacteria such as Azospirillum may affect mineral nutrition and plant growth indirectly rather than by supply of nitrogen. 相似文献
16.
Márcia G. Ventura Maria Do Carmo Freitas Adriano M. G. Pacheco 《Water, air, and soil pollution》2005,166(1-4):167-179
Selenium contents in the Portuguese (mainland) territory, resulting from a few environmental studies held since 1990 using lichens, vascular plants, soils and air particulate matter (APM), are presented and discussed herein. Values for Se in soils, epiphytic lichens and higher plants are within the typical ranges found in the literature. Compared to vascular plants, lichens display higher contents at the same locations. In what concerns Se in airborne particulates, all surveyed sites show values that are typical of urban areas. In two of such sites – Monchique and Carregado – Se concentrations in transplanted lichen thalli of the Parmelia genus (mostly, Parmelia sulcata Taylor) were compared to the results obtained from airborne matter, and a good correlation was found for the corresponding data-sets at either location. Other than the degree of association, it is especially noteworthy that the lichen transplants appear to accumulate much more Se at Monchique (a remote, rather clean site) than at Carregado (in the immediate vicinity of an oil-fired, power plant), even if its amount in the atmosphere is lower at the former location. 相似文献
17.
W. Hfner 《植物养料与土壤学杂志》1972,131(2):130-138
Uptake and adsorption of ferrous and ferric iron by sunflower plants The uptake of iron by 13 day-old sunflower seedlings in water culture experiments was studied using FeCl3, Fe-citrate and ferroammoniumsulfat (Mohr'sches Salz) in the-nutrient solution. By raising the N-, K- and Ca-content and lowering the P-content of the nutrient solution at the same time the iron content of the exudate in the FeCl3-treatment was increased up to 200 %. In the case of Fe-citrate, similar values were obtained only under aeration conditions of the nutrient medium. Application of iron as ferrous sulfate led to an increase of the iron content in the exudate and in the aerial plant parts amounting to about 200 and 400 %. respectively over that of the FeCl3 treatment. After 15 hr-uptake, most of the iron, taken up by the seedlings was in an unexchangeable form in the root system. The results give a further evidence for the peferential uptake of iron in the ferrous form. 相似文献
18.
Growth, development, and uptake of essential nutrients as influenced by nitrogen (N) form and growth stage was evaluated for ‘Freedom’ poinsettias (Euphorbia pulcherrima Willd. Ex Klotz.). Treatments consisted of five nitrate (NH4 +):ammonium (NO3 ‐) ratios (% NH4 +:% NO3 ‐) of 100:0, 75:25, 50:50, 25:75, and 0:100 with a total N concentration of 150 mg L‐1. Plants were grown in solution culture for ten weeks under greenhouse conditions. Nutrient uptake data was combined into three physiological growth stages. Growth stage I (GSI) included early vegetative growth (long days). Growth stage II (GSII) began at floral induction and leaf and bract expansion (short days). Growth stage III (GSIII) was from visible bud through anthesis and harvest. Dry weights for all plant parts and height increased as the ratio of NO3 ‐ increased. Leaf area and bract area were maximized with 25:75 and 50:50 N treatments, respectively. Nitrogen treatments significantly affected foliar nutrient concentrations with calcium (Ca++) and magnesium (Mg++) being highest when NO3 ‐ was the predominant N form. Uptake of each macronutrient was averaged across all treatments and divided into physiological growth stages (GS) to identify peak demand periods during the growth cycle. The greatest uptake of NH4 + and NO3 ‐ was from the early vegetative stage to floral induction (GSI). Phosphorus (P), potassium (K+), and Mg++ uptake were greatest from floral induction to visible bud (GSII) and Ca++ uptake remained relatively unchanged through GSI and GSII. Uptake was lowest for all nutrients from visible bud to anthesis (GSIII). Results from this study clearly indicate that peak demand periods for macronutrient uptake existed during the growth cycle of poinsettia. 相似文献
19.
Direct and residual effects of organic treatments and in combination with inorganic fertilizers applied to acid soils were studied in the okra–rice system. Among the treatments studied, vermicompost (V.C) and poultry manure improved soil pH and exhibited liming effect, whereas inorganic fertilizer decreased soil pH. Inorganic fertilizer contributed to 78% of net return in okra but the residual effect was observed in inorganic and V.C combination. Soil available nitrogen and potassium had increased at 100% recommended dose, compensated crop uptake at 75%, but depletion was observed at 50%. Uptake of nitrogen was higher for okra from inorganic fertilizer but higher phosphorus and potassium uptake from V.C was observed for rice. Organic treatments showed better correlation between soil pH and zinc (Zn) uptake by okra and significant residual effect on rice. But it reduced the solubility of iron (Fe) and its uptake by okra and indicated a negative correlation between pH and diethylene triamine penta acetic acid-extractable Fe2+. 相似文献
20.
Arshad Javaid 《Journal of plant nutrition》2013,36(10):1595-1618
ABSTRACT Arbuscular mycorrhizae (AM) are the symbiotic fungi that predominate in the roots and soils of agricultural crop plants. The most recognized beneficial effect of these fungi is to enhance host plant uptake of relatively immobile nutrients, in particular phosphorus (P), and several micronutrients. The AM fungi absorb inorganic P either from the soluble P pools in the soil, or from insoluble forms such as rock phosphates as well as from insoluble organic sources. Recent studies show that mycorrhizal fungi would have access to rock phosphate through localized alterations of pH and/or by the production of organic acid anions that may act as chelating agents. The AM colonization also improves plant N nutrition. Generally mycorrhizal symbiosis more influences on nitrogen (N) uptake and translocation if ammonium (NH4 +) rather than nitrate (NO3 ?) is the nitrogen source. However, under drought stress the role of mycorrhizae in NO3 ? transport to the root surface may be significant as the NO3 ? mobility is severely restricted due to its low concentration and diffusion rate under such circumstances. However, as yet little is known about the mechanism of N uptake by the AM fungi. Uptake of micronutrients is also influenced by mycorrhizal colonization. 相似文献