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1.
Soil P availability has been identified as one of the key factors controlling wetland productivity, structure, and function. Soil P fractions at different depths in newly formed wetlands along a salinity gradient in Yellow River Delta (China) were studied using a modified Hedley fraction method. The total P (Pt) content ranged from 471.1 to 694.9 mg kg–1, and diluted HCl‐extractable inorganic P (Dil‐HCl‐Pi) ranged from 324 to 524.2 mg kg–1. The Dil‐HCl‐Pi is the predominant P form in all profiles, with on average 70% of the Pt extracted as Pi. Organic P (Po) comprised (4.2 ± 2.0)% (mean ± SD) of the Pt, due to low organic‐matter content in coastal salt marsh ecosystems. The labile P (resin‐P, NaHCO3‐Pi, and NaHCO3‐Po) and moderately labile P (NaOH‐Pi and NaOH‐Po) concentrations were both low, ranged from 11.6 to 38.1 and 2.8 to 21.3 mg kg–1, respectively, constituting (3.7 ± 1.1)% and (2.0 ± 0.7)%, respectively, of Pt, suggesting low availability of P to plants in these soils. Our results suggested that vegetation cover significantly influenced soil P dynamics and availability. In particular, the labile P content under Tamarix chinensis increased significantly by 23.2%–145.5% compared with adjacent soils. These findings have important implications for wetland conservation or restoration and long‐term sustainable management of newly formed wetland ecosystems in the Yellow River Delta.  相似文献   

2.
We have tested to see if the generic set of NICA‐Donnan model parameters, used to describe isolated humic substances, can also describe soil humic substances in situ. A potentiometric back‐titration technique was used to determine the variable surface charge of two organic peat soils at three different ionic strengths. The non‐ideal, competitive‐adsorption NICA‐Donnan model was used to simulate the surface charge, by assuming a bimodal distribution of H+ affinity on the soil solid phase. The model provided an excellent fit to the experimental data. The Donnan volume, VD, varied slightly with ionic strength, although the variation was less than for humic substances in solution. The values obtained for the parameters that define the affinity distributions, the intrinsic proton binding constant (log Kiint) and the heterogeneity of the site (mi), were similar to those observed for isolated soil humic acids. The abundance of carboxylic groups in the whole soil represented 30% of the typical value for isolated soil humic acids. The composition of the organic matter of the whole soils, obtained by 13C CPMAS NMR, was comparable to the characteristic composition of soil humic acids.  相似文献   

3.
Abstract

Relatively insoluble sources of phosphorus (P) may require solubilization, and organic P (Po) may require hydrolysis to inorganic P (Pi) before P can be readily absorbed by plants roots. The mechanisms for these processes, however, are unknown. Root phosphatase (Pase) activity was measured to assess its relationships to P uptake by seven sorghum [Sorghum bicolor (L.) Moench] genotypes grown with Po (ethylammonium phosphate, glycerophosphate, and phenylphosphate) and Pi (KH2PO4, calcium tribasic phosphate, calcium pyrophosphate, aluminum phosphate, and ferric phosphate) in nutrient solutions in a greenhouse.

Plants grown with Po had lower root Pase activities than plants grown with Pi NB9040 and SC369–3–1JB (tolerant to low levels of P) had lower root Pase activities than CK60‐Korgi and SC33–9–8‐E4 (sensitive to low levels of P), with the other genotypes having intermediate root Pase activities. Higher root Pase activity was associated with lower root P concentrations, but Pase activity was not related to dry matter yield of roots. In experiments where genotypes were grown three weeks with KH2PO4 before being transferred to other sources of P, within four days root Pase activity patterns were similar to those for plants grown initially in the particular Po or Pi compound. Root Pase activity of sorghum plants appeared to be an indicator of P status or P deficiency stress in the plants, and not associated with making Po or Pi compounds more available for plant use.  相似文献   

4.
Some formulations of phosphite (Phi) have been recommended as a source of P nutrition for several crops including citrus even though there are known negative effects of Phi on plant growth. Changes in plant growth and metabolism after Phi application should be reflected in altered nutrient‐use efficiency and leaf photosynthesis. We carried out a greenhouse study using seedlings of two contrasting citrus (Citrus spp.) rootstocks, Carrizo citrange (CC) and Smooth Flat Seville (SFS), growing in either aerated hydroponic culture or sterilized native sandy soil. Plants were subjected to four P treatments: No P (control, P0); 0.5 mM Pi (PO4‐P); 0.25 mM Pi + 0.25 mM Phi (Pi + Phi), or 0.5 mM Phi (Phi). Photosynthetic characteristics, concentrations of total P (Pt) and soluble PO4‐P or PO3‐P in leaves and roots, and plant growth were evaluated after 80–83 d P treatments. Overall, the Pi plants had the highest Pt (total P) and total plant dry weight while the P0 plants had the lowest Pt but highest total root length and root‐to‐shoot ratio. Leaf chlorophyll (SPAD readings) and net assimilation of CO2 (ACO2) of the P0 and Phi plants were similarly lower than those of Pi and Pi + Phi plants. Growth responses of the Pi + Phi treatment were intermediate between the Pi and Phi treatments. Although Phi increased Pt and soluble‐PO4‐P concentration in leaves and roots above the P0 treatment, this did not translate into increased plant growth. In fact, the Phi treatment had some phytotoxic symptoms, impaired P‐ and N‐utilization efficiency for biomass production as well as lower nutrient‐use efficiency in the photosynthetic process. Thus, these two rootstocks could not use Phi as a nutritional source of P.  相似文献   

5.
Humic substances improve the efficiency of different iron (Fe) sources overcoming Fe deficiency chlorosis of plants. However, applied at high rates, they can promote negative effects on plants. The main objective of this work was to study the potential adverse effect of three humic acids from different origin when they were applied with two effective Fe sources for plants: Fe- ethylenediaminedihydroxyphenylacetic acid (EDDHA) and Vivianite. To this end, an experiment with lupin (Lupinus albus L.) was performed involving two factors: (i) Fe source, and (ii) humic substances from three different origin (composted cork, leonardite, and compost obtained from a mixture of olive husk with cotton gin trash) applied at 0, 0.1, and 0.5 g organic carbon (C) kg?1 of growing media. At the rates used, humic substances promoted adverse effects on plant development, chlorophyll meter readings, and Fe content in lupin grown in calcareous media. Overall, the effect on dry matter and Fe content in plants was more relevant when Fe was supplied with Vivianite, the effect on chlorophyll meter readings being more significant when Fe was applied as Fe-EDDHA. Differences were also observed depending on the source of humic substances, those from leonardite promoting the greatest decrease in dry matter in roots and shoots. These humic substances possessed the highest values of spectroscopy index for aromaticity (A254 ). On the other hand, the application of humic substances from olive husk compost, which exhibited the lower aromaticity index, resulted in the smallest decrease in dry matter production and chlorophyll meter readings. Dry matter in roots decreased logarithmically with increased values of the estimates of the amounts of aromatic compounds accumulated in the growing media (R2 = 0.92; P < 0.01) with Vivianite as Fe source. Thus, the effects decreasing dry matter production, particularly in roots, and chlorophyll meter readings can be ascribed at least partially to the presence of phytotoxic aromatic compounds in humic substances.  相似文献   

6.
Although the fungicidal properties of phosphite have been recognized, its potential as a fertilizer is still being debated. The information on how phosphite affects the growth and quality of plants in relation to phosphate (Pi) also remains unknown. This study was conducted to investigate the effect of phosphite in relation to Pi on growth and quality parameters of lettuce (Lactuca sativa L.). The results showed that addition of phosphite to the nutrient solution at different rates ranging from 0.05 to 2 mM significantly increased total P, water‐extractable Pi, and phosphite in both shoots and roots, but did not improve plant growth under various Pi supplies (0.05, 0.1, 0.15, and 0.3 mM as Pi levels for approximately 50%, 80%, 90%, and 100% of the maximum plant growth, respectively), indicating that phosphite was well absorbed by roots and mobile inside the plants, but did not provide any P nutrition. Also, no stimulating effect of any Pi–phosphite combination was observed. The effect of phosphite on plant growth was strongly dependent on the level of Pi supply. In general, application of phosphite up to 2 mM did not influence the growth of Pi‐sufficient plants. However, plants fertilized with Pi for about 90% of maximum growth were still vulnerable to phosphite at 2 mM. The negative effect of phosphite was found even at concentrations as low as 0.2 mM, when plants were supplied with Pi adequate for about 80% of maximum growth or less. At 0.05 mM, phosphite had marginal effects on plant growth under all the Pi levels. Although phosphite itself had little influence on the ascorbate and mineral concentrations of lettuce, its application to Pi‐deficient plants may decrease the mineral concentrations of plants brought about by the inhibitory effect of phosphite on root growth and hence nutrient uptake. Since phosphite is an effective fungicide for lettuce, care should be taken on Pi supplies prior to application of phosphite products to minimize the harmful effects.  相似文献   

7.
The kinetic parameters of nitrate uptake (Imax, Km and Cmin) were evaluated in young seedlings of Triticum durum L., cv. Appulo, exposed to nitrate and/or to soil‐extracted humic acids (HAs) of different molecular weight. The uptake was enhanced after induction at low levels of nitrate (50 μM KNO3), while it was inhibited after induction at higher concentrations (2000 μM). The kinetic parameters of uptake were selectively influenced by pre‐treatment with HAs: total (TE) and, at a greater extent, low (LMS, < 3500 Da) molecular size humic fraction increased either the nitrate uptake rate (Imax) and the efficiency of the whole transport system (low Km and Cmin), while an opposite result was evidenced in high molecular size (HMS, > 3500 Da)‐treated plants. An additive effect was shown when nitrate and humic substances were provided simultaneously: the uptake rate was enhanced in TE‐ and LMS‐treated plants, but was strongly delayed in HMS‐treated plants. Removal of nitrate and/or humic fractions de‐induced the system and NO3 uptake rate decreased. Exposure to HAs was not able to induce nitrate reductase activity in root and leaf tissues. Inhibitors of protein synthesis p‐fluorophenylalanine and cycloheximide reversed the positive effect of LMS fraction on nitrate uptake. This would support the hypothesis of a promoting effect of HAs on the molecular expression of proteins of the nitrate transport system.  相似文献   

8.
The aim of this study was to determine how phosphorus (P) concentration affects growth, concentration and distribution of nutrients in Leucospermum cordifolium ‘Flame Spike’ (Proteaceae). The trials were performed at the School of Agriculture (ETSIA) of the University of La Laguna (28° 28′ 43′′ N, 16° 19′ 7′′ W) with 64 plants (1-year-old) grown for 12 months in silica sand, fed with nutrient solutions containing different levels of Pi (5, 10, 15 and 20 mg L?1). At 6, 9, and 12 months, whole plants were taken from each experimental unit and divided into root, stem (main, first, second, and third growth) and leaves (adult, first, second, and third growth), which were measured, weighed, and analyzed. The data enabled a nutritional diagnosis, including the limiting P concentrations and nutrient interactions. P concentrations above 5 mg L?1 caused a reduction in growth, which in the third samples was significant (P < 0.05). Plants treated with 15 and 20 mg L?1 P attained similar dry weights (P > 0.05). Some young leaves showed a certain degree of chlorosis, probably due to iron (Fe) deficiency. Fully developed young leaves (YFEL) were suitable for nutritional diagnosis of P, and the P concentration of the nutrient solution affected the foliar manganese (Mn) concentration. This latter factor was related to the zinc (Zn) concentration in the roots.  相似文献   

9.
The aim of this work was to study the effect of arbuscular mycorrhizal fungus Glomus mosseae on growth and nitrogen (N) metabolism of durum wheat (Tritcum durum) under various P soil contents. The analyses were extended to macro and micronutrient tissue concentrations, nitrate reductase and glutamine synthetase activities, as well as protein, aminoacids, pyridine dinucleotides and adenine nucleotides. Arbuscular mycorrhiza increased wheat growth in soil in which P availability was low and nitrate was the dominant N form. The root colonization occurred at the highest level in plants grown in limiting soil P and was inversely related to soil P content. The micorrhizal wheat plants contained also the highest concentrations of macro (P, K, Ca, N) and micronutrients (Fe, Zn, Mn) as well as free amino acids, protein, NAD, NADP, AMP, ADP, ATP in roots and leaves. In particular, the micronutrient tissue concentrations (Zn, Mn) supported that mycorrhiza actively modulated their uptake limiting interferences and optimizing growth better than the plant roots, like a very efficient “rootstock”. Control plants grown at the highest soil P did not reach the same concentration as the mycorrhizal plants. Nitrate reductase activities in the roots of mycorrhizal plants were higher than in the control ones, while glutamine synthetase activities were highest in the leaves. Protein and amino acids concentrations, as well as AMP, ADP, ATP, NAD(P), and NAD(P)H were also higher than in the control. Among the free amino acids in the roots, the high levels of glutamine, asparagine, arginine, support the view that ammonium was transferred through the arbuscules to the root cells where it was re‐assimilated in the cortical cells, forming high N : C ratio‐amino acids. They were transferred to the leaves where all the other N compounds could be largely synthesized using the carbon skeletons supplied by photosynthesis.  相似文献   

10.
Chinese cabbage plants [Brassica pekinensis (Lour) Rupr. cv. Nagaoka 50] were cultivated experimentally for two years (1993 and 1994) using a semi‐forcing technique of floating rowcovers, polyethylene (T1), polypropylene (T2), versus no floating row‐covers, control (T0). Five samplings were made, taking four plants per each replication and total phosphorus (P) (Ptotal), inorganic P (Pi), and calculated organic P (Porg) were determined as well as foliar acid phosphatase activity (FAPA). The aerial and root temperatures of the treatments T1 and T2 exceeded those of T0. The Ptotal concentration showed no significant variations with treatment, whereas the Pi concentrations increased in Ti and T2 and Porg decreased in both treatments with respect to T0. The FAPA was influenced a similar way as Pi, raising with temperature. The contents (mg plant‐1) of Ptolal, Pi, and Porg were greater in T1 and T2 than in T0, and this could be due to the fact that the highest temperatures (root and aerial zone) generated by the plastic rowcovers favored the absorption of P, thereby boosting FAPA and the fresh and dry weights, and yield.  相似文献   

11.
ABSTRACT

In vitro grown kiwifruit (Actinidia deliciosa, Liang and Ferguson) plantlets were treated with two humic fractions distinguished by two different relative molecular mass and characterized through their elemental composition and 13Carbon (C) nuclear magnetic resonance. The effects exerted on plant growth, root morphology, and nutrition were evidenced by means of leaves and roots mineral content, root respiration, and nitrate reductase activity. The two humic substances differentially influenced the studied parameters. The lower molecular fraction humic substance, endowed with a higher content of phenolic and carboxylic groups, caused an enhanced content of micro- and macro-elements, together with a higher root respiration at lower concentrations (0.5–1 mg C L? 1). The high molecular fraction humic substance, needed higher concentrations (> 5 mg C L? 1) in order to achieve similar effects. This fraction also caused major changes on root morphology. The ability to improve micronutrient assimilation, in particular iron, confirmed the agronomic importance of humic substances on soil fertility.  相似文献   

12.
Abstract

Humic substances from two different types of peat ‐ Sphagnum and Carex ‐ were obtained by using either alkali extractants, O.IM NaOH, O.IM KOH, and 0.25M KOH, or solvents containing sodium pyrophosphate (O.IM Na4P2O7, or O.IM NaOH/Na4P2O7). The alkalis released considerably greater amounts of humic substances from the Sphagnum peat than the extractants containing pyrophosphate, whereas the opposite occurred in the Carex peat, the two greatest yields being obtained with 0.25M KOH in Sphagnum peat and with O.IM NaOH/Na4P2O7 in Carex. As shown by the spectroscopic and chemical analyses, humic acids released from both peats by extractants containing Na4P2O7 are generally more oxidized than those obtained by any of the alkali solutions. Also, humic acids extracted from the Sphagnum peat by any of the solvents generally exhibit lower molecular sizes, more pronounced aliphatic characteristics, and a higher degree of oxidation than those extracted from the Carex peat.

Results of gel permeation chromatography indicate that humic acids obtained from Sphagnum peat by either O.IM NaOH or O.IM KOH extraction show a similar distribution of molecular sizes with a predominance of compounds with a molecular weight greater than 50,000, whereas the use of 0.25M KOH enhances the release of partially degraded humic substances. Also, humic acids extracted from the same peat with 0.1M Na4P2O7 show a considerable amount of molecules of low molecular weight, but much fewer of these compounds are obtained when 0.1M NaOH/Na4P2O7 extraction is employed. In Car ex peat, molecular size distribution does not seem to depend on the type of extractant used for solubilization of their humic acids.  相似文献   

13.
Purpose

The present study was designed to assess the potential effects of low-molecular-weight organic acids on the activation of inorganic phosphorus, obtain exact information on the acidity effect of proton and complex effect of organic anion in P availability, and determine the components among phosphorus fractions that contributed the most to inorganic phosphorus activation in black soil.

Materials and methods

Both oxalic and citric acids treated with different concentrations and pH values were carefully selected. The activating amounts of total inorganic phosphorus and individual phosphorus fractions were estimated. Path analysis was used to analyze the direct and indirect effects on inorganic phosphorus activation.

Results and discussion

The amount of total activating-Pi increased as the concentrations of oxalic and citric acids increased. When the concentrations were ≤?1.0 mmol L?1, oxalic acid exhibited a lower capability than citric acid in total activating-Pi, but when the concentrations were ≥?1.5 mmol L?1, oxalic acid exhibited a higher capability. The amount of total activating-Pi decreased as pH of LMWOAs increased. LMWOAs-induced Pi activation might be attributed to combine acidity and complex effects.

Conclusions

Correlation analysis showed that the activation of total Pi was significantly correlated with the activation of H2O-Pi, NaHCO3-Pi, NaOH-Pi, and HCl-Pi (p?<?0.05). Path analysis revealed that soil activating-H2O-Pi mainly affected Pi activation through an indirect path. The contribution of activating-NaHCO3-Pi alone was maximal on the total activating-Pi by both the direct and indirect effects, followed by activating-NaOH-Pi and activating-HCl-Pi.

  相似文献   

14.
Tobacco plants (Nicotiana tabacum L. cv NC82) were supplied with (NH4)2SO4, or NH4Cl at root‐zone pH of 6.0 and 4.5 in hydroponic culture for 28 days. Dry matter accumulation, total N and C content, and leaf area and number were not affected by the NH4 + source or root‐zone pH. Plants supplied with NH4C1 accumulated up to 1.2 mM Cl g DW‐1, but accumulated 37% less inorganic H2PO4 and 47% less SO4 2‐ than plants supplied with (NH)2SO4. The large Cl accumulation resulted in NH4C1 –supplied plants having a 31% higher inorganic anion (NO3 , H2, PO4 , SO4 2‐, and Cl) charge. This higher inorganic anion charge in the NH4C1‐supplied plants was balanced by a similar increase in K+ charge. Plants supplied with NH4Cl accumulated greater concentrations of Cl in leaves (up to 5.1% of DW) than plants supplied with (NH4)2SO4 (less than ‐% DW). Despite the high Cl concentration of leaves in NH4Cl supplied plants, these plants showed no symptoms of Cl toxicity. This demonstrates that toxicity symptoms are not due solely to an interaction between high Cl concentration in tissue and NH4 + nutrition. The increase in root‐zone acidity to pH 4.5 from 6.0 did not induce toxicity symptoms.  相似文献   

15.
Information concerning sources and sinks of available P in soil is needed to improve soil P management and protect water quality. This study, conducted from 1989 to 1998 on a Sultan silt loam soil (Aquantic Xerochrept), determined the annual P removal rate by corn (Zea mays L.) and P transformation as affected by P rate and winter cover cropping. Treatments included two P rates (0 and 44 kg P ha–1) applied to corn at planting each year. All cover crops received 19.6 kg P ha–1 at seeding each fall. Also included was a control without any cover crop and with no P addition. Corn yield and P uptake were affected by P fertilizer additions, but not by cover crops. A fairly constant amount of P was supplied from indigenous soil P when no external P was added. When the amount of P added exceeded that removed by corn, the excess P was converted mainly to NaOH-extractable inorganic P (NaOH-Pi). When the amount of P applied was below that removed by corn, indigenous soil NaOH-Pi acted as a source of available P for the plant. With no reduction of organic P (Po) extractable by NaOH or NaHCO3, the contribution from Po to the available P pool appeared limited. The role of NaOH-Pi in P availability in the soil was substantiated by its significant correlation with labile NH4Cl-extractable P (NH4Cl-P; r2 =0.60, P <0.001) or NaHCO3-Pi (r2 =0.81, P <0.001) pools. The NaOH-Pi for the soil reflected the changes in soil P resulting from past fertilizer P input and P removal by the crops.Scientific Paper Number 0005-34  相似文献   

16.
Beneficial effects of aluminum (Al) on plant growth have been reported for plant species adapted to acid soils. However, mechanisms underlying the stimulatory effect of Al have not been fully elucidated. The aim of this study was to determine the possible contribution of photosynthesis, antioxidative defense, and the metabolism of both nitrogen and phenolics to the Al‐induced growth stimulation in tea (Camellia sinensis [L.] Kuntze) plants. In hydroponics, shoot growth achieved its maximum at 50 μM Al suply (24 μM Al3+ activity). A more than threefold increase of root biomass was observed for plants supplied with 300 μM Al (125 μM Al3+ activity). Total root length was positively related to root Al concentrations (r = 0.98). Chlorophyll a and carotenoid concentrations and net assimilation rates were considerably enhanced by Al supply in the young but not in the old leaves. Activity of nitrate reductase was not influenced by Al. Higher concentrations of soluble nitrogen compounds (nitrate, nitrite, amino acids) and reduction of protein concentrations suggest Al‐induced protein degradation. This occurred concomitantly with enhanced net CO2‐assimilation rates and carbohydrate concentrations. Aluminum treatments activated antioxidant defense enzymes and increased free proline content. Lowering of malondialdehyde concentrations by Al supply indicates that membrane integrity was not impaired by Al. Leaves and roots of Al‐treated plants had considerably lower phenolic and lignin concentrations in the cell walls, but a higher proportion of soluble phenolics. In conclusion, Al‐induced growth stimulation in tea plants was mediated by higher photosynthesis rate and increased antioxidant defense. Additionally, greater root surface area may improve water and nutrient uptake by the plants.  相似文献   

17.
水磷耦合烤烟养分吸收分配规律研究   总被引:2,自引:1,他引:1  
为探究烤烟适宜的水磷耦合模式及其对氮、磷、钾养分吸收积累的影响。采用田间小区试验,试验设置3种灌水水平和施磷水平,分别为低水(W_1:0.50 L/株)、中水(W_2:1.00 L/株)、高水(W_3:2.00 L/株)和低磷(P_1:32 kg/hm^2)、中磷(P_2:64 kg/hm^2)、高磷(P_3:96 kg/hm^2),研究了不同施磷量和灌水量条件下烤烟对氮磷钾养分吸收积累的影响。结果表明:施磷量相同时,灌水处理能够明显增加烟株对氮、磷、钾养分的吸收积累量,表现为:W_3P_i>W_2P_i>W_1P_i>CK_i(其中i=1或2或3);当灌水量相同时,增加施磷量也有利于烟株对氮磷钾养分的吸收积累,且在施磷水平为96 kg/hm^2时表现较好,表现为:W_iP_3>W_iP_2>W_iP_1;高磷水平下,灌水量为1.00,2.00 L/株时,W_3P_3和W_2P_3处理烟株对氮磷钾养分的吸收积累量差异不显著;烟株和根、茎、叶各器官对钾的吸收量高于氮和磷,氮、磷、钾在根、茎、叶器官中的分配顺序呈现叶>茎>根的变化规律;在烟株的不同生育期,对养分的吸收积累量和积累强度存在差异。烟株对养分的吸收积累主要在旺长期,烟叶是养分的主要吸收积累器官;施磷量为96 kg/hm^2,灌水量为1.00~2.00 L/株的水磷耦合处理在促进烟株对氮磷钾养分的吸收积累方面效果较好。烤烟施肥中要注意调整氮磷钾的施用比例和水磷耦合配比。  相似文献   

18.
The effects of different forms and concentrations of N in the rooting medium on the CO2/H2O gas exchange of leaves of the pedunculate oak (Quercus robur L.) were investigated. Two-year-old seedlings were grown in nutrient solutions containing low (1.8 mM) or high (4.8 mM) concentrations of NH4+, 3.6 mM NO3?, or both NH4+ and NO3? (1.8 mM + 1.8 mM). In various sets of plants subjected to these N treatments, the following parameters were determined: biomasses of leaves and fine roots, leaf area-related net photosynthesis at light saturation (A) and leaf conductance (g), foliar concentrations of chlorophylls, N, Ca2+, Mg2+ and K+ and the ash alkalinity of the leaves (as a measure of the carboxylate content). In all treatments, the leaves were equally well supplied with nutrients. Oaks grown in high NH4+ concentrations produced significantly smaller leaf and root biomasses. Compared to oaks cultivated with both N forms or with low NH4+ concentration, oaks grown with high NH4+ supply showed lower values of A and g, but no significant differences in ash alkalinity and leaf area-related chlorophyll concentrations. Oaks fed with NO3? as the only N form had an intermediate biomass production, but low values of A and g. The time courses of A in the different treatments closely followed the patterns of g. In all N treatments, the same linear relationship was found between A and g, indicating that, within a rather wide range, the variation in the form and amount of supplied N does not affect the instantaneous water use efficiency of young pedunculate oaks.  相似文献   

19.
王萍  胡江  冉炜  徐国华 《土壤学报》2008,45(3):503-509
环境和食品中砷标准提高后,砷污染及其有关的食品安全问题更加受到广泛的关注。磷对植物吸收和累积砷的影响及其作用机制仍有很大争论。本文利用水培试验,研究了0.025~1.0 mmol L-1范围内7个供磷水平下50μmol L-1AsO43-胁迫对微型番茄生长、砷和磷的吸收及两个磷酸盐转运体基因(LePT1和LePT2)表达的影响。在0.025~0.4 mmol L-1的缺磷条件下,砷对番茄的生长有明显抑制作用。在缺磷状态下,增加磷供应能显著减少番茄体内砷的浓度。约58%的砷累积在番茄根部,根部砷的浓度较地上部高10倍以上。砷抑制番茄对磷的吸收只出现在严重缺磷(0.025~0.05 mmol L-1)条件下。此外,外界砷的存在对LePT1、LePT2基因的表达影响不显著。从本文的结果来看,番茄吸收过程中的磷砷相互作用在缺磷条件下更明显,提高供磷水平可降低番茄体内砷含量,缓解砷对番茄的胁迫作用。  相似文献   

20.
Abstract

Humic acids have many benefits for plant growth and development, and these effects may be maximized if these materials are combined with micronutrient applications. In the present study, pot experiments were conducted to evaluate the effects of zinc (Zn) humate and ZnSO4 on growth of wheat and soybean in a severely Zn‐deficient calcareous soil (DTPA‐Zn: 0.10 mg kg?1 soil). Plants were grown for 24 (wheat) and 28 days (soybean) with 0 or 5 mg kg?1 of Zn as either ZnSO4 or Zn humate. Zinc humate used in the experiments was obtained from Humintech GmbH, Germany, and contained 5% of Zn. When Zn was not supplied, plants rapidly developed visible symptoms of Zn deficiency (e.g., chlorosis and brown patches on young leaves in soybean and necrotic patches on middle‐aged leaves in wheat). Adding Zn humate eliminated Zn‐deficiency symptoms and enhanced dry matter production by 50% in soybean and 120% in wheat. Zinc‐humate and ZnSO4 were similarly effective in increasing dry matter production in wheat; but Zn humate increased soybean dry matter more than ZnSO4. When Zn was not supplied, Zn concentrations were 6 mg kg?1 for wheat and 8 mg kg?1 for soybean. Application of Zn humate and ZnSO4 increased shoot Zn concentration of plants to 36 and 34 mg kg?1 in wheat and to 13 and 18 mg kg?1 in soybean, respectively. The results indicate that soybean and wheat plants can efficiently utilize Zn chelated to humic acid in calcareous soils, and this utilization is comparable to the utilization of Zn from ZnSO4. Under Zn‐deficient soil conditions, plant growth and yield can be maximized by the combined positive effects of Zn and humic acids.  相似文献   

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