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1.
The effect of Zn deficiency in wheat (Triticum aestivum L. cv. Ares) on the release of Zn mobilizing root exudates was studied in nutrient solution. Compared to Zn sufficient plants, Zn deficient plants had higher root and lower shoot dry weights. After visual Zn deficiency symptoms in leaves appeared (15–17 day old plants) there was a severalfold increase in the release of root exudates efficient at mobilizing Zn from either a selective cation exchanger (Zn-chelite) or a calcareous soil. The release of these root exudates by Zn deficient plants followed a distinct diurnal rhythm with a maximum between 2 and 8 h after the onset of light. Re-supply of Zn to deficient plants depressed the release of Zn mobilizing root exudates within 12 h to about 50%-, and after 72 h to the level of the control plants (Zn sufficient plants). The root exudates of Zn deficient wheat plants were equally effective at mobilizing Fe from freshly precipitated FeIII hydroxide as Zn from Zn-chelite. Furthermore, root exudates from Fe deficient wheat plants mobilized Zn from Zn-chelite, as well as Fe from FeIII hydroxide. Purification of the root exudates and identification by HPLC indicated that under Zn as well as under Fe deficiency, wheat roots of the cv. Ares released the phytosiderophore 2′-deoxymugineic acid. Additional experiments with barley (Hordeum vulgare L. cv. Europa) showed that in this species another phytosiderophore (epi-3-hydroxymugineic acid) was released under both Zn and Fe deficiencies. These results demonstrate that the enhanced release of phytosiderophores by roots of grasses is not a response mechanism specific for Fe deficiency, but also occurs under Zn deficiency. The ecological relevance of enhanced release of phytosiderophore also under Zn deficiency is discussed.  相似文献   

2.
Maize was grown for 36 days in solution culture with roots either under axenic conditions or in the presence of rhizosphere organisms. In other experiments with sterile roots the plants were grown with different concentrations of potassium. At the end of the experiments sugars, organic acids and amino acids in the nutrient solutions were determined. Under axenic conditions the exudates consisted of up to 65% sugars, up to 33% organic acids and only up to 2% amino acids. The same substances were detected in non-sterile nutrient solutions. In the presence of microorganisms fructose, arabinose and the predominating glucose decreased to almost one half, while sucrose was not affected. The amounts of organic acids were not changed by microbial growth. The main amino acid, glutamic acid, was nearly doubled by the presence of microorganisms, whereas other amino acids remained unchanged. The lower O2 content of the nutrient solutions of non-sterile roots suggested microbial decomposition of monosaccharides. In another experiment with roots grown under axenic conditions and with different K treatments low K supply significantly increased the total amounts of sugars, organic acids and amino acids exuded g?1 root dry matter. As in the previous experiment glucose, fumaric and oxalacetic acid as well as glutamic and aspartic acid dominated in the respective fractions. Again sugars and organic acids represented the major quantity of exudates, while amino acids amounted to less than 2%. In an additional experiment with another cultivar, with nitrate as N source and a 5-day longer growth period, somewhat different results were obtained. In the exudates sugars were found in lower amounts, probably due to a higher growth rate. Under these conditions organic acids were the prevailing root exudates. Unlike sugars and amino acids, their total quantity was not affected by K nutrition, but the proportion of malic acid increased with increasing K supply, while oxalacetic acid dominated at low K nutrition. Similarly the total amount of organic acids within the root was independent of K nutrition. However malic acid content increased with increasing K application, while the likewise dominating citric and oxalacetic acid decreased.  相似文献   

3.
The effect of zinc nutritional status of the plant on the release of zinc mobilizing root exudates was studied in various dicotyledonous (apple, bean, cotton, sunflower, tomato) and graminaceous (barley, wheat) plant species grown in nutrient solutions. In all species, zinc deficiency increased root exudation of amino acids, sugars and phenolics. However, the root exudates of zinc deficient dicotyledonous species did not enhance zinc mobilization from a synthetic resin (Zn chelite), or a calcareous soil, although mobilization of iron from FeIII hydroxide was increased. By contrast in the graminaceous species, root exudates from zinc deficient plants greatly increased mobilization of both zinc and iron from the various sources. These differences in capability of mobilization of zinc and iron between the plant species are the result of an enhanced release of phytosiderophores with zinc deficiency in the graminaceous species.  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.
Dicotyledons cope with ion (Fe) shortage by releasing low-molecular-weight organic compounds into the rhizosphere to mobilize Fe through reduction and complexation mechanisms. The effects induced by these root exudates on soil mineralogy and the connections between Fe mobilization and mineral weathering processes have not been completely clarified. In a batch experiment, we tested two different kinds of organic compounds commonly exuded by Fe-deficient plants, i.e., three organic acids (citrate, malate, and oxalate) and three flavonoids (rutin, quercetin, and genistein), alone or in combination, for their ability to mobilize Fe from a calcareous soil and modify its mineralogy. The effect of root exudates on soil mineralogy was assessed in vivo by cultivating Fe-deficient and Fe-sufficient cucumber plants (Cucumis sativus L.) in a RHIZOtest device. Mineralogical analyses were performed by X-ray powder diffraction. The batch experiment showed that citrate and, particularly, rutin (alone or combined with organic acids or genistein) promoted Fe mobilization from the soil. The combinations of rutin and organic acids modified the soil mineralogy by dissolving the amorphous fractions and promoting the formation of illite. These mineralogical alterations were significantly correlated with the amount of Fe mobilized from the soil. The RHIZOtest experiment revealed a drastic dissolution of amorphous components in the rhizosphere soil of Fe-deficient plants, possibly caused by the intense release of phenolics, amino acids, and organic acids, but without any formation of illite. Both batch and RHIZOtest experiments proved that exudates released by cucumber under Fe deficiency concurred to the rapid modification (on a day-scale) of the mineralogy of a calcareous soil.  相似文献   

6.
Knowledge of the composition and quantity of organic substances released from roots of different plant species is necessary for understanding the chemical and biological processes in the rhizosphere. The present study was undertaken to quantify low molecular weight organic acids (LMWOAs) released from roots of five cultivars/lines of durum wheat (Triticum turgidum var. durum L.): Kyle, Sceptre, DT618, DT627, and DT637 and four cultivars/ lines of flax (Linum usitatissiumum L.): Somme, Flanders, AC Emerson, and YSED 2. Plants were grown in sterile nutrient solution cultures and amounts of organic acids exuded by roots were analyzed by gas chromatography. The LMWOAs varied significantly among both durum wheat and flax cultivars and oxalic, malonic, fumaric, succinic, acetic, malic, citric and tartaric acids were detected in root exudates of both species. Generally, oxalic and acetic acids were predominant in durum wheat exudates and oxalic, acetic and malic acids were predominant in flax root exudates. High oxalic acid concentrations occurred in root exudates of durum wheat cultivars DT627 and DT637, and flax cultivar YSED 2. Compared with the other durum wheat cultivars, Kyle released the lowest total amount of LMWOAs, whereas among the flax cultivars, YSED 2 had the highest total amount of acids secreted from roots. The data showed that the release of LMWOAs from roots was cultivar dependent. The results provide valuable background information for studying the role of root exudates in soil‐plant relationships.  相似文献   

7.
A previous study demonstrated that cabbage was P efficient compared to carrot and potato. However, calculating plant P uptake by a mechanistic simulation model based on P transport by diffusion and mass flow, P uptake of roots according to the Michaelis‐Menten kinetics, and morphological root characteristics including root hairs, revealed that these parameters could explain only 2/5 of the total P uptake of cabbage, but 4/5 of that of carrot and potato (Dechassa et al., 2003). Therefore, it was hypothesized that a higher root exudation of organic anions may enhance P mobilization and hence P uptake of cabbage. The objective of this research was to determine root exudation of organic anions by the three species, and to investigate the influence of plant age and dark/light period on organic‐anion exudation by cabbage. Experiments were conducted in a growth chamber in nutrient solution with or without P. Organic anions were determined in root exudates and in root tissue. With cabbage and potato, P deficiency induced exudation of citrate and succinate, respectively. Citrate‐exudation rate of P‐deficient cabbage plants was correlated with accumulation of citrate in root tissue. In contrast, high succinate‐exudation rates in potato were not correlated with an increased concentration in root tissue. For carrot, no change was observed in the exudation of any of the organic anions in response to P deficiency. The results also showed that succinate‐ and citrate‐exudation rates of cabbage roots increased with increased plant age. There was also a significant increase in exudation rates of organic anions of cabbage roots during the light period of the day. It was concluded that cabbage had the ability to exude large amounts of citrate in response to P deficiency by which it can additionally enhance its P‐uptake efficiency, whereas carrot and potato showed little evidence of possessing such a mechanism.  相似文献   

8.
The effect of the zinc (Zn) nutritional status on the rate of phyto‐siderophore release was studied in three wild grass species (Hordeum murinum, Agropyron orientale, and Secale cereale) grown in nutrient solution under co‐trolled environmental conditions. These wild grasses are highly “Zn‐efficient”; and grow well on severely Zn‐deficient calcareous soils in Turkey (DTPA‐extractable Zn was 0.12 mg/kg soil and CaCO3 was 37%). In all wild grasses studied, Zn deficiency reduced shoot growth but had no effect on root growth. Low amounts of phytosiderophores were released from roots of all wild grasses adequately supplied with Zn. In plants grown without Zn, release of phytosiderophores progressively increased with the onset of visual Zn deficiency symptoms, such as inhibition of shoot elongation and appearance of chlorotic and necrotic patches on leaves. Compared to Zn‐sufficient plants, phytosiderophore release increased 18–20‐fold in deficient plants. HPLC analysis of root exudates showed that the dominating phytosiderophore in Zn‐deficient Agropyron and Hordeum was 3‐epi‐hydro‐xymugineic acid (epi‐HMA) and was 3‐hydroxy‐mugineic acid (HMA) in Secale. Besides HMA, epi‐HMA and mugineic acid (MA) were also detected in exudates of Zn‐deficient Secale. The results indicate the importance of phytosiderophores in adaptation of wild grasses to Zn‐deficient calcareous soils. Phytosiderophores might enhance mobilization of Zn from sparingly soluble Zn pools and from adsorption sites, both in the rhizosphere and within the plants.  相似文献   

9.
ABSTRACT

Root exudate is derived from plant metabolites and its composition is affected by plant nutrient status. A deficiency of mineral nutrients, such as nitrogen (N) and phosphorus (P), strongly affects the type and amount of plant metabolites. We applied a metabolite profiling technique to investigate root exudates of rice plants under N and P deficiency. Oryza sativa was grown in culture solution containing two N levels (0 and 60 mg N L?1) or two P levels (0 and 8 mg P L?1). Shoot extracts, root extracts, and root exudates were obtained from the rice plants 5 and 15 days after transplanting and their metabolites were determined by capillary electrophoresis/time-of-flight mass spectrometry. Shoot N concentration and dry weight of rice plants grown at ?N level were lower than those of plants grown at +N level. Shoot P concentration and dry weight of rice plants grown at ?P level were lower than those of plants grown at +P level. One hundred and thirty-two, 127, and 98 metabolites were identified in shoot extracts, root extracts, and root exudates, respectively, at the two N levels. One hundred and thirty-two, 128, and 99 metabolites were identified in shoot extracts, root extracts, and root exudates, respectively, at the two P levels. Seventy-seven percent of the metabolites were exuded to the rhizosphere. The concentrations of betaine, gamma-aminobutyric acid, and glutarate in root exudates were higher at both ?N and ?P levels than at their respective high levels. The concentration of spermidine in root exudates was lower at both ?N and ?P levels than at their respective high levels. The concentrations of the other metabolites in root exudates were affected differently by plant N or P status. These results suggest that rice roots actively release many metabolites in response to N and P deficiency.  相似文献   

10.
The effects of nitrogen (N‐) and phosphorus (P‐) deficiency, isolatedly or in combination, on growth, nitrogenous fraction, and inorganic phosphate in xylem exudade, and photosynthesis of common bean (Phaseolus vulgaris L. cv. Negrito) were investigated. Plants were grown in nutrient solution adjusted daily to pH 5.5 and aerated continuously. Ten days after emergence mineral deficiency was imposed. Plants were then supplied with high N (7.5 mol m‐3) or low N (0.5 mol m‐3), and also with high P (0.5 mol m‐3) or low P (0.005 mol m‐3). All sampling and measurements were made 28 days after emergence. N‐ or P‐deprivation brought about large decreases in total leaf area by inhibiting the emergence of new leaves and primarily the expansion of the leaves. The specific leaf area did not change under N‐ but decreased under P‐limitation. The decreased shoot to root ratio in all deficiency treatments was a consequence of a lowering mass of above‐ground organs, especially of leaves.

The content of chlorophylls declined significantly only under N‐deficiency alone; carotenoids declined under both N‐ and combined N‐ and P‐limitation. No alteration in amino acid concentration in xylem exudate occurred in plants experiencing N‐starvation, while ureides increased by 79%, and nitrate and inorganic phosphate decreased greatly. Under P‐deprivation, amino acids and nitrate in xylem sap dropped by about half; ureides were held relatively constant, and phosphate was severely depressed. Total upward translocation of N through xylem was estimated to be about 16% higher in N‐deficient plants than in plants without mineral limitation, but leaf N levels in the former were lower as compared to control plants. The net carbon (C) assimilation decreased similarly regardless of the imposed deficiency treatment. Such a decrease was mainly determined by non‐stomatal factors. In general, no additive effect between N‐ and P‐limitation on any of measured parameters was observed.  相似文献   

11.
Plant root systems mediate ecological processes in the rhizosphere through the exudation of organic compounds. Although exudate composition is thought to depend strongly on plant nutrient status, little is known about the influence of multi‐nutrient stresses. In this study, we examined responses to short‐term (3 d) nutrient limitation in Helianthus annuus (common sunflower), and root exudates were collected for 2, 4, or 6 h with the trap‐solution method. Root exudates, analyzed by means of gas chromatography‐mass spectrometry, consisted of over 60 sugars, sugar alcohols, amino acids, organic acids, and phosphates, with sugars and organic acids generally detected in the highest quantities. Twenty‐five of the detected metabolites, including half of the organic acids, sugars, and sugar alcohols, differed in relative abundance among the three sampling intervals, exhibiting higher abundance in sampling intervals greater than 2 h. Similarly, 24 of the detected metabolites, including half of the amino acids, phosphates, and sugar alcohols, were affected by nutrient supply, with 20 exhibiting higher abundance in the high‐nutrient treatment. Fumaric acid, quinic acid, and glucose were detected at significantly higher levels in the low‐nutrient treatment, potentially representing an adaptive response to nutrient limitation in sunflower. However, as sampling interval exerted a strong influence on the apparent effects of nutrient supply, future studies should consider the potential impacts of sampling‐interval length in comparative analyses of genotypes or treatments.  相似文献   

12.
Previous studies describe the suitability of a new type of phosphorus (P) fertilizer, called “rhizosphere‐controlled fertilizer” (RCF), to supply available P to plants while reducing soil phosphorus fixation. In order to explore the involvement of organic acid root exudation in P uptake from RCF, we investigated the relationship between shoot and root P concentrations, and the concentration of the main polycarboxylic organic acids in roots, shoots, and plant exudates. Plant species with different P‐acquisition efficiency (low: maize; medium: chickpea; high: lupin) were grown in hydroponics with three different P fertilizers: The water‐insoluble P fraction of RCF (RCF); Phospal, a slow‐release source of phosphate composed of calcium and aluminum phosphates (PH); monopotassiumphosphate (KP), and a control treatment without P (P–). RCF was as efficient as KP in supplying P to plants in the case of chickpea and lupin, and slightly less efficient than KP in maize. However, P from PH was not available for maize and less available compared to KP and RCF in chickpea and lupin. This variation reflects the different efficiencies in P acquisition for the three plant species. Except in the case of maize, plants receiving KP presented the lowest concentration of organic acids in roots and exudates, while those plants suffering severe P deficiency (P– and PH) showed the highest organic acid concentration. However, RCF had a high concentration of organic acids in roots and exudates, as well as a high P concentration in the shoot indicating that P uptake from RCF is enhanced due to root release and action of specific organic acids.  相似文献   

13.
The objective of this work was to study the effect of root and foliar application of two commercial products containing amino acids from plant and animal origin on iron (Fe) nutrition of tomato seedlings cultivated in two nutrient media: lime and normal nutrient solutions. In the foliar‐application experiment, each product was sprayed with 0.5 and 0.7 mL L–1 2, 7, 12, and 17 d after transplanting. In the root application experiment, 0.1 and 0.2 mL L–1 of amino acids products were added to the nutrient solutions. In both experiments, untreated control plants were included as well. Foliar and root application of the product containing amino acids from animal origin caused severe plant‐growth depression and nonpositive effects on Fe nutrition were found. In contrast, the application of the product from plant origin stimulated plant growth. Furthermore, significantly enhanced root and leaf FeIII‐chelate reductase activity, chlorophyll concentration, leaf Fe concentration, and FeII : Fe ratio were found in tomato seedlings treated with the product from plant origin, especially when the amino acids were directly applied to the roots. These effects were more evident in plants developed under lime‐induced Fe deficiency. The positive results on Fe uptake may be related to the action of glutamic acid, the most abundant amino acid in the formulation of the product from plant origin.  相似文献   

14.
The composition of root‐derived substances is of great importance for the understanding of processes in the rhizosphere. Therefore, methods allowing a comprehensive collection and chemical analysis of the organic root exudates are necessary. In this study, we compare different methods with regard to their suitability to collect and characterize root exudates. Because the percolation or water logging method failed to quantitatively extract root exudates, a dipping method was developed which allowed an almost complete sampling of coldwater‐soluble root exudates. By 14CO2 labeling of the shoots the composition of root exudates was found to be influenced by plant species and growth stage. In comparison to pea plants maize plants had a higher share of carboxylic acids and a lower share of sugars. Younger maize plants exuded considerably higher amounts of 14C labeled organic substances per g root dry matter than older ones. During plant development the relative amount of sugars decreased at the expense of carboxylic acids. The described methods are well suited for the elucidation of the influence of growth factors on root exudation.  相似文献   

15.
根分泌物与禾本科植物对缺铁胁迫的适应机理   总被引：8，自引：0，他引：8  
本文系统地总结了自然基金重点项目根分泌物在根际微生态系统中的营养机理的研究进展和部分主要成果。研究表明,养分专一性根分泌物是植物营养遗传特性控制基因的标记物,它受某一养分缺乏的诱导,是在植物体内合成并可通过主动分泌作用进入根际的代谢产物。它的合成和分泌只受该养分胁迫的专一诱导和控制,只要改善这一营养状况就能抑制或阻止其合成和分泌。当植物缺乏这一养分时,植物体可通过自身的调节能力,合成专一性物质并自根分泌到根际,促进该养分的活化并提高植物对其吸收利用效率,从而达到克服或缓解该营养胁迫的目的。用单基因突变材料进行的研究表明,植物铁载体的生物合成和吸收利用是受单基因控制的过程。这一发现不仅使人类有可能运用生物学研究技术来解决营养缺乏问题,而且也为有效地利用自然资源、降低生产成本、减少环境污染提供了可能性。麦根酸类(mugineic.acids)植物铁载体(phytosiderophores)在缺铁禾本科植物体内的生物合成,从植物根内向根际的分泌、在根际环境中对铁的活化及植物对F63+植物铁载体螯合体的吸收四个过程组成了禾本科植物对缺铁胁迫的适应机理。植物铁载体只在早晨日出后2～6h内大量分泌的节律性增加了它们在根际土壤中的相对浓度,减少了它们与土壤颗粒的接触和被吸附;分泌部位集中在微生物尚未侵染的根尖避开了微生物的破坏和分解,同时也增加了它们在土壤微区中的相对浓度。分泌作用和螯合作用不受介质pH值和Ca2+离子浓度影响的特性使该机理在经常出现缺铁现象的石灰性土壤上具有特殊意义。研究结果还表明,缺铁可以诱导激活根细胞原生质膜上可能存在的Fe3+植物铁载体复合体的专一性吸收和运载蛋白,高pH值和CaCO3对这一蛋白的载体功能只有很小的抑制作用,即使在pH值和CaCO3含量都较高的石灰性土壤上,也能有效地发挥作用。这一结论揭示了小麦等禾本科植物适应铁胁迫的实质及其生态学意义。  相似文献   

16.
Despite numerous studies on phytosiderophores (PS) there is still an open question whether nickel (Ni) deficiency induces release of PS from graminaceous plant roots. Seedlings of two wheat cultivars (Triticum aestivum L. cvs. Rushan and Kavir) and a triticale cultivar (X. triticosecale) were grown in Ni‐free nutrient solution (Ni‐deficient, Ni–) and with 10 µM NiSO4 (Ni‐sufficient, Ni+, control). Root exudates were collected weekly for 4 weeks and the amount of PS in the root exudates was measured. The response to Ni deficiency on the release of PS differed between species. Roots of Rushan and triticale exuded higher PS in response to Ni‐deficient conditions. Nickel deficiency significantly enhanced shoot Fe and Zn concentrations in wheat, while it decreased shoot Fe and Zn concentrations in triticale. In Kavir, PS exudation was decreased by Ni deficiency at weeks 3 and 4 and the reduced release of PS from roots of Kavir was accompanied by lower concentrations of Fe and Zn in plant roots but higher Fe and Zn concentrations in shoot tissue. The PS release by Kavir was triggered by a Ni‐induced Zn deficiency particularly in the shoots. According to the results, it is suggested that in the studies concerning the phytosiderophore release under Ni deficiency, special attention should be given to different responses among and within cereals and to the plant Zn or Fe nutritional status.  相似文献   

17.
Seedlings of Norway spruce (Picea abies [L.] Karst.), which had been grown under sterile conditions for three months, were treated for one week in a hydroculture system with either 500 μM AlCl3 or 750 μM CaCl2 solutions at pH 4. Organic acids were determined in hot‐water extracts of ground root tissue. Oxalate (3.3—6.6 μmol (g root dry weight)—1) was most abundant. Malate, citrate, formate, acetate, and lactate concentrations ranged between 1—2 μmol (g root dry weight)—1. Organic substances and phosphate found in the treatment solutions at the end of the experimental period were considered to be root exudates. Total root exudation within a 2‐day period ranged from 20—40 μmol C (g root weight)—1. In root exudates, organic acids, and total carbohydrates, total amino acids, and total phenolic substances were quantified. Citrate and malate, although present in hot‐water extracts of root tissue, were not detected in root exudates. Phosphate was released from Ca‐treated plants. In Al treatments, there was indication of Al phosphate precipitation at the root surface. Oxalate and phenolics present in the exudates of Norway spruce seedlings are ligands that can form stable complexes with Al. However, concentrations of these substances in the treatment solutions were at micromolar levels. Their importance for the protection of the sensitive root apex under natural conditions is discussed.  相似文献   

18.
This study assesses the influence of saccharides in the rhizodeposition on the phosphate solubilizing ability of rhizosphere bacteria. Water‐soluble rhizodeposits were analyzed of 14C‐labeled pea plants (Pisum sativum, cv. ‘Grapis’) which were grown at two different levels of P‐nutrition. The sugars produced were fed in vitro either as single compounds or as synthetic mixtures to three bacterial strains and the ability of the bacteria to mobilize Ca3(PO4)2 was measured. The relative glucose proportion of pea exudates decreased under P deficiency while the content of galactose, ribose, xylose and fucose increased. In vitro feeding of single sugars and sugar mixtures showed that the ability of Pseudomonas fluorescens (PsIA12) to dissolve tertiary calcium phosphate was lower with pentoses and the mixed sugars of the P‐deficient plants than with glucose. On the other hand, the shifted sugar pattern observed under P deficiency increased the phosphate mobilization ability of Pantoea agglomerans (D5/23) and Azospirillum sp. (CC 322) considerably. This observation can only partly be explained by the acidification of the nutrient medium. Bacteria also produced different carboxylic anions depending on sugar supply. In addition to low‐molecular mono‐, di‐, and tricarboxylic acids which are known as P‐solubilizing substances, sugar acids also played an important role in cultures D 5/23 and CC 322.  相似文献   

19.
不同青菜品种吸锌能力差异及与根系分泌物的关系   总被引：20，自引：4，他引：20  
青菜 [Brassica campestris var. chinensis(L.)Makino]不同品种对土壤中锌的累积吸收有明显差异[1] ,我们推断根系分泌物在青菜吸收锌的过程中可能起着重要作用。因此在本项研究中 ,对 2个不同锌利用效率的青菜品种的根系分泌物组成、数量及其与锌吸收的关系进行了探讨。结果表明 ,2种锌水平下 ,五月慢根系分泌物中低分子量有机酸及氨基酸的总量均明显高于黑油白菜 ,缺锌时品种间差异达 0.05显著水平 ;缺锌条件下 ,五月慢根系分泌物中草酸、丙氨酸的含量同样显著高于黑油白菜。五月慢在缺锌时有较高的根系分泌物总量及其草酸、丙氨酸含量都显著增加 ,这可能是五月慢具有较高累积吸锌量及锌利用效率的重要原因之一。  相似文献   

20.
Some plants respond to Fe‐deficiency stress by inducing Fe‐solubilizing reactions at or near the root surface. In their ability to solubilize Fe, dicotyledonous plants are more effective than monocotyledonous plants. In this study we determined how representative plants differ in their response when subjected to Fe‐deficiency stress in a calcareous soil and in nutrient solutions. Iron‐inefficient genotypes of tomato, soybean, oats, and corn all developed Fe chlorosis when grown in soil, whereas Fe‐efficient genotypes of these same species remained green. The same genotypes were grown in complete nutrient solutions and then transferred to nutrient solutions containing N (as NO3 ‐) and no Fe.

The T3238 FER tomato (Lycopersican esculentum Mill.) Fe‐efficient) was the only genotype that released significant amounts of H from the roots (the pH was lowered to 3.9) and concomitantly released reductants. Under similar conditions, Hawkeye soyhean [Glycine max (L.) Merr.] released reductants but the solution pH was not lowered. Both Fe‐inefficient and Fe‐efficient genotypes of oats (Avena sativa L.) and corn (Zea mays L.) released insufficient H or reductant from their roots to solubilize Fe; as a result, each of these genotypes developed Fe‐deficiency (chlorosis).

The marked differences observed among these genotypes illustrate the genetic variability inherent within many plant species. A given species or genotype may accordingly not be adapted to a particular soil. Conversely, a given species or genotype may be found (or developed) that is precisely suited for a particular soil. In this event, the need for soil amendments may be reduced or eliminated.  相似文献   

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