Distribution of Carboxylates and Acid Phosphatase and Depletion of Different Phosphorus Fractions in the Rhizosphere of a Cereal and Three Grain Legumes

This study investigates the distribution of carboxylates and acid phosphatases as well as the depletion of different phosphorus (P) fractions in the rhizosphere of three legume crop species and a cereal, grown in a soil with two different levels of residual P. White lupin (Lupinus albus L.), field pea (Pisum sativum L.), faba bean (Vicia faba L.) and spring wheat (Triticum aestivum L.) were grown in small sand-filled PVC tubes to create a dense root mat against a 38-μm mesh nylon cloth at the bottom, where it was in contact with the soil of interest contained in another tube. The soil had either not been fertilised (P0) or fertilised with 15 (P15) kg P ha⁻¹ in previous years. The mesh size did not allow roots to grow into the soil, but penetration of root hairs and diffusion of nutrients and root exudates was possible, and a rhizosphere was established. At harvest, thin (1 mm) slices of this rhizosphere soil were cut, down to a 10-mm distance from the mesh surface. The rhizosphere of white lupin, particularly in the P0 treatment, contained citrate, mostly in the first 3 mm, with concentrations decreasing with distance from the root. Acid phosphatase activity was enhanced in the rhizosphere of all species, as compared with bulk soil, up to a distance of 4 mm. Phosphatase activity was highest in the rhizosphere of white lupin, followed by faba bean, field pea and wheat. Both citrate concentrations and phosphatase activities were higher in P0 compared with P15. The depletion of both inorganic (P_i) and organic (P_o) phosphorus fractions was greatest at the root surface, and decreased gradually with distance from the root. The soil P fractions that were most depleted as a result of root activity were the bicarbonate-extractable (0.5 M) and sodium hydroxide-extractable (0.1 M) pools, irrespective of plant species. This study suggests that differences among the studied species in use of different P pools and in the width of the rhizosphere are relatively small.     

Residual nitrogen contribution from grain legumes to succeeding wheat and rape and related microbial process

The residual N contribution from faba bean (Vicia faba L.), pea (Pisum sativum L.) and white lupin (Lupinus albus L.) to microbial biomass and subsequent wheat (Triticum aestivum L.) and oilseed rape (Brassica napus L.) was studied in a greenhouse experiment. The grain legumes were ¹⁵N labelled in situ with a stem feeding method before incorporated into the soil, which enables the determination of N rhizodeposition. Wheat and rape were subsequently grown on the soil containing the grain legume residues (incl. ¹⁵N-labelled rhizodeposits) and were harvested either twice at flowering and at maturity or once at maturity, respectively. The average total N uptake of the subsequent crops was influenced by the legume used as precrop and was determined by the residue N input and the N₂-fixation capacity of the legume species. The succeeding crops recovered 8.6–12.1% of the residue N at maturity. Similar patterns were found for the microbial biomass, which recovered 8.2–10.6% of the residue N. Wheat and rape recovered about the same amount of residue N. The absolute contribution of soil derived N to the subsequent crops was similar in all treatments and averaged 149 mg N pot^–1 at maturity. At flowering 17–23% of the residue derived N was recovered in the subsequent wheat and in the microbial biomass; 70% of the residue N was recovered in the microbial biomass in the flowering stage and decreased to about 50% at maturity. In contrast, the recovery in wheat and rape constituted only 30% at flowering and increased to 50% at maturity in all treatments, indicating that the residual N uptake by the subsequent wheat was apparently supplied by mobilisation of residue N temporarily immobilised in the microbial biomass.     

Wheat, canola and grain legume access to soil phosphorus fractions differs in soils with contrasting phosphorus dynamics

Despite the high phosphorus (P) mobilizing capacity of many legumes, recent studies have found that, at least in calcareous soils, wheat is also able to access insoluble P fractions through yet unknown mechanism(s). We hypothesized that insoluble P fractions may be more available to non-legume plants in alkaline soils due to increased dissolution of the dominant calcium(Ca)-P pool into depleted labile P pools, whereas non-legumes may have limited access to insoluble P fractions in iron(Fe)- and aluminium(Al)-P dominated acid soils. Four crop species (faba bean, chickpea, wheat and canola) were grown on two acid and one alkaline soil under glasshouse conditions to examine rhizosphere processes and soil P fractions accessed. While all species generally depleted the H₂O-soluble inorganic P (water Pi) pool in all soils, there was no net depletion of the labile NaHCO₃-extractable inorganic P fraction (NaHCO₃ Pi) by any species in any soil. The NaOH-extractable P fraction (NaOH Pi) in the alkaline soil was the only non-labile Pi fraction depleted by all crops (particularly canola), possibly due to increases in rhizosphere pH. Chickpea mobilized the insoluble HCl Pi and residual P fractions; however, rhizosphere pH and carboxylate exudation could not fully explain all of the observed Pi depletion in each soil. All organic P fractions appeared highly recalcitrant, with the exception of some depletion of the NaHCO₃ Po fraction by faba bean in the acid soils. Chickpea and faba bean did not show a higher capacity than wheat or canola to mobilize insoluble P pools across all soil types, and the availability of various P fractions to legume and non-legume crops differed in soils with contrasting P dynamics.     

The Development of Desiccation-tolerance and Maximum Seed Quality During Seed Maturation in Six Grain Legumes

‘Physiological maturity’, i.e. the time when seedsreach their maximum dry weight during development, occurredwhen maturation drying on the parent plant in the field hadreduced seed moisture content to approximately 60 per cent infaba bean (Vicia faba L.), lentil (Lens culinaris Medic.), chickpea(Cicer arietinum L.), white lupin (Lupinus albus L.), soya bean(Glycine max [L.] Merr.) and pea (Pisum sativum L.) The onsetof desiccation-tolerance, i.e. the ability of seeds to germinatefollowing harvest and rapid artificial drying, coincided withphysiological maturity, except in pea where it occurred a littleearlier at about 70 per cent moisture content. Maximum seedquality as determined by maximum viability, minimum seedlingabnormalities and maximum seedling size occurred in pea, chickpeaand lupin when seeds were harvested for rapid drying at physiologicalmaturity; but for maximum seed quality in the other speciesmaturation drying had to proceed further - to about 45 per centmoisture content in soya bean and to about 30 per cent moisturecontent in lentil and faba bean seed crops. Much of this variationamongst the six species, however, was due to differences inthe variation in maturity within each seed crop. Results forindividual pods showed that peak maturity, i.e. maximum seedquality following harvest and rapid artificial drying, was achievedin all six species once maturation drying had reduced the moisturecontent of the seeds to 45–50 per cent. In pea, faba beanand soya bean there was a substantial decline in viability andan increase in seedling abnormalities when harvest was delayedbeyond the optimal moisture content for harvest.     

Phosphorus pools and other soil properties in the rhizosphere of wheat and legumes growing in three soils in monoculture or as a mixture of wheat and legume

Background and aims

Phosphorus and nitrogen availability and forms are affected by soil properties as well as by plant species and further modulated by soil microbes. Additionally, close contact of the roots of two plant species may affect concentrations and forms of N and P. The aim of this study was to assess properties related to N and P cycling in the rhizosphere of wheat and legumes grown in monoculture or in wheat/legume mixtures in three soils differing in pH.

Methods

Faba bean, white lupin and wheat were grown in three soils differing in pH (4.8, 7.5 and 8.8) in monoculture or in mixed culture of wheat and legumes. Rhizosphere soil was collected at flowering and analyzed for P pools by sequential fractionation, available N as well as community structure of bacteria, fungi, ammonia oxidizers, N₂-fixers and P mobilizers by polymerase chain reaction (PCR)—denaturing gradient gel electrophoresis (DGGE).

Results

Soil type was the major factor determining plant growth, rhizosphere nutrient dynamics and microbial community structure. Among the crop species, only faba bean had a significant effect on nitrification potential activity (PNA) in all three soils with lower activity compared to the unplanted soil. Soil type and plant spieces affected the community composition of ammonia-oxidizing archaea (AOB), ammonia-oxidizing archaea (AOA), N₂-fixers (nifH), P mobilizers (ALP gene) and fungi, but not that of bacteria. Among the microbial groups, the AOA and nifH community composition were most strongly affected by crop species, cropping system and soil type, suggesting that these groups are quite sensitive to environmental conditions. All plants depleted some labile as well as non-labile P pools whereas the less labile organic P pools (NaOH extractable P pools, acid extractable P pools) accumulated in the rhizosphere of legumes. The pattern of depletion and accumulation of some P pools differed between monoculture and mixed culture as well as among soils.

Conclusions

Plant growth and rhizosphere properties were mainly affected by soil type, but also by crop species whereas cropping system had the least effect. Wheat and the legumes depleted less labile inorganic P pools in some soils whereas less labile organic P pools (NaOH extractable P, acid extractable P) accumulated in the rhizosphere of legumes.     

Phosphorus acquisition characteristics of cotton (Gossypium hirsutum L.), wheat (Triticum aestivum L.) and white lupin (Lupinus albus L.) under P deficient conditions

A rhizobox experiment was conducted to examine the P acquisition characteristics of cotton (Gossypium hirsutum L.), wheat (Triticum aestivum L.) and white lupin (Lupinus albus L.) under P-deficient conditions. We aimed to identify whether cotton is physiologically efficient at acquiring P through release of protons, phosphatases or carboxylates. Plants were pre-grown in the upper compartment of rhizoboxes filled with a sand and soil mixture to create a dense root mat against a 53 μm polyester mesh. For each species, two P treatments (0 and 20 mg P kg^?1) were applied to the upper compartment in order to create P-deficient and P-sufficient plants. At harvest, the upper compartment with intact plants was used for collection of root exudates while the lower soil compartment was sliced into thin layers (1 mm) parallel to the rhizoplane. Noticeable carboxylates release was only detected for white lupin. All P-deficient plants showed a capacity to acidify their rhizosphere soil to a distance of 3 mm. The activity of acid phosphatase was significantly enhanced in the soil-root interfaces of P-stressed cotton and wheat. Under P-deficient conditions, the P depletion zone of cotton from the lower soil compartment was narrowest (<2 mm) among the species. Phosphorus fractionation of the rhizosphere soil showed that P utilized by cotton mainly come from NaHCO₃–P_i and NaOH–P_o pools while wheat and white lupin markedly depleted NaHCO₃–P_i and HCl–P pools, and the depletion zone extended to 3 mm. Wheat also depleted NaOH–P_o to a significant level irrespective of P supply. The study suggests that acquisition of soil P is enhanced through P mobilization by root exudates for white lupin, and possibly proton release and extensive roots for wheat under P deficiency. In contrast, the P acquisition of cotton was associated with increased activity of phosphatases in rhizosphere soil.     

Effects of climate and vegetation on soil nutrients and chemistry in the Great Basin studied along a latitudinal-elevational climate gradient

Background and aims

Roots have morphological plasticity to adapt to heterogeneous nutrient distribution in soil, but little is known about crop differences in root plasticity. The objective of this study was to evaluate root morphological strategies of four crop species in response to soil zones enriched with different nutrients.

Methods

Four crop species that are common in intercropping systems [maize (Zea mays L.), wheat (Triticum aestivum L.), faba bean (Vicia faba L.), and chickpea (Cicer arietinum L.)] and have contrasting root morphological traits were grown for 45 days under uniform or localized nitrogen and phosphorus supply.

Results

For each species tested, the nutrient supply patterns had no effect on shoot biomass and specific root length. However, localized supply of ammonium plus phosphorus induced maize and wheat root proliferation in the nutrient-rich zone. Localized supply of ammonium alone suppressed the whole root growth of chickpea and maize, whereas localized phosphorus plus ammonium reversed (maize and chickpea ) the negative effect of ammonium. The localized root proliferation of chickpea in a nutrient-rich zone did not increase the whole root length and root surface area. Faba bean had no significant response to localized nutrient supply.

Conclusions

The root morphological plasticity is influenced by nutrient-specific and species-specific responses, with the greater plasticity in graminaceous (eg. maize) than leguminous species (eg. faba bean and chickpea).     

The Rate of Morphogenesis of Embryos and Seeds in Four Species of Grain Legumes

Comparative embryo development has been studied histologicallyin Lupinus albus, Lupinus mutabilis, Vicia faba, Pisum sativumand Latkyrus latifolius. The detailed histology of the stagesof embryo formation up to the early differentiation of tissuesof the seed is reported. The rate of embryogenesis has beentimed through 15 stages of development from anthesis and comparativerates of tissue formation established between the species. Themain observation was the slow rate of morphogenesis of embryosand seeds in Lupinus albus in comparison with the very rapidrate observed in Pisum sativum. A long period at the globularembryo stage, when embryo morphogenesis was inactive contributedto the extended development time of embryos and seeds in Lupinusalbus. Slow differentiation of reproductive tissues in L. albusdetermines late maturity in seeds and pods. Lupinus albus, white lupin, L. mutabilis, tarwi, Vicia faba, faba bean, Pisum sativum, pea, Lathyrus latifolius, everlasting pea, embryo development     

Nitrogen Fixation of Faba Bean (Vicia faba L.) Interacting with a Non-legume in Two Contrasting Intercropping Systems

A field experiment was carried out to quantify biological nitrogen fixation (BNF) using the ¹⁵N isotope natural abundance method in maize (Zea mays L.)/faba bean (Vicia faba L.) and wheat (Triticum aestivum L.)/faba bean intercropping systems. Faba bean was yielding more in the maize/faba bean intercropping, but not in the wheat/faba bean intercropping. Biomass, grain yield and N acquisition of faba bean were significantly increased when intercropped with maize, and decreased significantly with wheat, irrespective of N-fertilizer application, indicating that the legume could gain or lose productivity in an intercropping situation. There was yield advantage of maize/faba bean intercropping, but no in wheat/faba bean intercropping. The grain yield of the faba bean intercropped with maize was greater than that of faba bean monoculture due to increases of the stems per plant and the pods per stem of faba bean. N fertilization inhibited N fixation of faba bean in maize/faba bean and wheat/faba bean intercropping and faba bean monoculture. The responses of different cropping systems to N-fertilizer application, however, were not identical, with competitive intercropping (wheat/faba bean) being more sensitive than facilitative intercropping (maize/faba bean). Intercropping increased the percentage of N derived from air (%Ndfa) of the wheat/faba bean system, but not that of the maize/faba bean system when no N fertilizer was applied. When receiving 120 kg N/ha, however, intercropping did not significantly increase %Ndfa either in the wheat/faba bean system or in the maize/faba bean system in comparison with faba bean in monoculture. The amount of shoot N derived from air (Ndfa), however, increased significantly when intercropped with maize, irrespective of N-fertilizer application. Ndfa decreased when intercropped with wheat, albeit not significantly at 120 kg N/ha. Ndfa was correlated more closely with dry matter yield, grain yield and competitive ratio, than with %Ndfa. This indicates that that total dry matter yield (sink strength), not %Ndfa, was more critical for the legume to increase Ndfa. The results suggested that N fixation could be improved by yield maximization in an intercropping system.     

An overview of rhizosphere processes related with plant nutrition in major cropping systems in China

Rhizosphere processes of individual plants have been widely investigated since 1904 when the term “rhizosphere” was first put forward. However, little attention has been paid to rhizosphere effects at an agro-ecosystem level. This paper presents recent research on the rhizosphere processes in relation to plant nutrition in main cropping systems in China. In the peanut (Arachis hypogaea L.)/maize (Zea mays L.) intercropping system, maize was found to improve the Fe nutrition of peanut through influencing its rhizosphere processes, suggesting an important role of phytosiderophores released from Fe-deficient maize. Intercropping between maize and faba bean (Vicia faba L.) was found to improve nitrogen and phosphorus uptake in the two crops compared with corresponding sole crop. There was a higher land equivalent ratio (LER) in the intercropping system of maize and faba bean than the treatment of no root interactions between the two crops. The increased yield of maize intercropped with faba bean resulted from an interspecific facilitation in nutrient uptake, depending on interspecific root interactions of the two crops. In the rotation system of rice (Oryza sativa L.)-wheat (Triticum aestivum L.) crops, Mn deficiency in wheat was caused by excessive Mn uptake by rice and Mn leaching from topsoil to subsoil due to periodic cycles of flooding and drying. However, wheat genotypes tolerant to Mn deficiency tended to distribute more roots to deeper soil layer and thus expand their rhizosphere zones in the Mn-deficient soils and utilize Mn from the subsoil. Deep ploughing also helped root penetration into subsoil and was propitious to correcting Mn deficiency in wheat rotated with rice. In comparison, oilseed rape (Brassica napus L.) took up more Mn than wheat through mobilizing sparingly soluble soil Mn due to acidification and reduction processes in the rhizosphere. Thus, oilseed rape was tolerant to the Mn-deficient conditions in the rice-oilseed rape rotation. Oxidation reactions on root surface of rice also resulted in the formation of Fe plaque in the rice rhizosphere. Large amounts of Zn were accumulated on the Fe plaque. Zinc uptake by rice plants increased as Fe plaque formed, but decreased at high amounts of Fe plaque. It is suggested that to fine-tune cropping patterns and optimize nutrient management based on a better understanding of rhizosphere processes at an agro-ecosystem level is crucial for increasing nutrient use efficiency and developing sustainable agriculture in China.     

Crop nitrogen use and soil mineral nitrogen accumulation under different crop combinations and patterns of strip intercropping in northwest China

Increasing crop nitrogen use efficiency while also simultaneously decreasing nitrogen accumulation in the soil would be key steps in controlling nitrogen pollution from agricultural systems. Long-term field experiments were started in 2003 to study the effects of intercropping on crop N use and soil mineral N accumulation in wheat (Triticum aestivum L. cv 2014)/maize (Zea mays L. cv Shendan16), wheat/faba bean (Vicia faba L. cv Lincan No. 5) and maize/faba bean intercropping and monocropping systems. Monocropping was compared with two types of strip intercropping: continuous intercropping (two crops intercropped continuously on the same strips of land every year) and rotational intercropping (two crops grown adjacently and rotated to the other crop??s strip every year). Maize/faba bean intercropping had greater crop N uptake than did wheat/faba bean or wheat/maize. Wheat/maize accumulated more mineral N in the top 140 cm of the soil profile during the co-growth stage from maize emergence to maturity of wheat or faba bean. Continuously intercropped maize substantially decreased soil mineral N accumulation under wheat and faba bean rows (60?C100 cm soil depth) at maize harvest. Soil mineral N accumulation under wheat rows increased with rotational intercropping with faba bean. Rotational intercropping may potentially alleviate the adverse effects of wheat on N use by other crops and increase the nitrogen harvest index of wheat, maize and faba bean. Intercropping using species with different maturity dates may be more effective in increasing crop N use efficiency and decreasing soil mineral N accumulation.     

Characterization of Bacterial Community Structure in Rhizosphere Soil of Grain Legumes

Molecular techniques were used to characterize bacterial community structure, diversity (16S rDNA), and activity (16S rRNA) in rhizospheres of three grain legumes: faba beans (Vicia faba L., cv. Scirocco), peas (Pisum sativum L., cv. Duel) and white lupin (Lupinus albus L., cv. Amiga). All plants were grown in the same soil under controlled conditions in a greenhouse and sampled after fruiting. Amplified 16S rDNA and rRNA products (using universal bacterial primers) were resolved by denaturing gradient gel electrophoresis (DGGE). Distinct profiles were observed for the three legumes with most of the bands derived from RNA being a subset of those derived from DNA. Comparing the total bacterial profiles with actinomycete-specific ones (using actinomycete-specific primers) highlighted the dominance of this group in the three rhizospheres. 16S PCR and RT-PCR products were cloned to construct libraries and 100 clones from each library were sequenced. Actinomycetes and proteobacteria dominated the clone libraries with differences in the groups of proteobacteria. Absence of β-subdivision members in pea and γ-subdivision members of proteobacteria in faba bean rhizosphere was observed. Plant-dependent rhizosphere effects were evident from significant differences in the bacterial community structure of the legume rhizospheres under study. The study gives a detailed picture of both residing and „active” bacterial community in the three rhizospheres. The high abundance of actinomycetes in the rhizospheres of mature legumes indicates their possible role in soil enrichment after the legumes are plowed into the soil as biofertilizers.     

Bioavailability of zinc and phosphorus in calcareous soils as affected by citrate exudation

Aims

Zinc (Zn) and phosphorus (P) deficiency often occurs at the same time and limits crop production in many soils. It has been suggested that citrate root exudation is a response of plants to both deficiencies. We used white lupin (Lupinus albus L.) as a model plant to clarify if citrate exuded by roots could increase the bioavailability of Zn and P in calcareous soils.

Methods

White lupin was grown in nutrient solution and in two calcareous soils in a rhizobox. Rhizosphere soil solution was sampled to determine citrate, metals and P. Based on the measured citrate concentrations, a soil extraction experiment with citrate as extractant was done.

Results

Absence of Zn triggered neither cluster root formation nor citrate exudation of white lupin grown in nutrient solution, whereas low P supply did. The maximum citrate concentration (～1.5?mM) found in the cluster rhizosphere soil solution of one soil mobilized P, but not Zn. In the other soil the highest citrate concentration (～0.5?mM) mobilized both elements.

Conclusions

White lupin does not respond to low Zn bioavailability by increasing citrate exudation. Such a response was observed at low P supply only. Whether Zn and P can be mobilized by citrate is soil-dependent and the possible controlling mechanisms are discussed.     

Triticum aestivum shows a greater biomass response to a supply of aluminium phosphate than Lupinus albus, despite releasing fewer carboxylates into the rhizosphere

The relationship between carboxylate release and the ability of plants to access phosphorus from AlPO4 and to detoxify aluminium was studied by comparing species with a low and high rate of carboxylate release, Triticum aestivum (wheat) and Lupinus albus (white lupin), respectively. Species were supplied with P at 10, 20, 40 or 100 mg P kg-1 sand in the form of sparingly soluble AlPO4 or soluble KH2PO4; control plants did not receive any P. Triticum aestivum was significantly better than L. albus at accessing P from AlPO4, despite accumulating fewer carboxylates in its rhizosphere. Rhizosphere pH of L. albus did not vary with form or level of P supply, while the rhizosphere pH of T. aestivum increased with the level of P supplied. Based on the evidence in the present study, a model is proposed to explain the poor performance of L. albus, whereby the release of carboxylates and associated protons reduces the chelating ability of exuded carboxylates, thus reducing P acquisition and increasing Al toxicity.     

Phloem translocation of gibberellins in three species of higher plants

Phloem sap was collected from white lupin (Lupinus albus L.), cowpea (Vigna unguiculata L.) and castor bean (Ricinus communis L.) and analysed for gibberellins (GAs) using gas chromatography-mass spectrometry (GC-MS). A large number of GAs were found in the phloem exudate of all three species, particularly where the sap was collected from pods (white lupin and cowpea) and in these legumes GAs representing both the early C-13-hydroxylation and non-hydroxylation pathways of biosynthesis were identified. In the sap collected from the vegetative tissues of castor bean the number of GAs identified was fewer than that in the other species, representing mainly the non-hydroxylation pathway. Data from sap collected from the pedicel and stylar ends of pods and by making feeds of radiolabelled GAs to seeds in situ in white lupin indicate that the GAs present in the phloem are derived mainly from the vegetative tissues of the plant. No evidence for metabolism of GAs in the phloem could be found.     

Chickpea and white lupin rhizosphere carboxylates vary with soil properties and enhance phosphorus uptake

Chickpea and white lupin roots are able to exude large amounts of carboxylates, but the resulting concentrations in the rhizosphere vary widely. We grew chickpea in pots in eleven different Western Australian soils, all with low phosphorus concentrations. While final plant mass varied more than two-fold and phosphorus content almost five-fold, there were only minor changes in root morphological traits that potentially enhance phosphorus uptake (e.g., the proportion of plant mass allocated to roots, or the length of roots per unit root mass). In contrast, the concentration of carboxylates (mainly malonate, citrate and malate, extracted using a 0.2 mM CaCl₂ solution) varied ten-fold (averaging 2.3 mol g^–1 dry rhizosphere soil, approximately equivalent to a soil solution concentration of 23 mM). Plant phosphorus uptake was positively correlated with the concentration of carboxylates in the rhizosphere, and it was consistently higher in soils with a smaller capacity to sorb phosphorus. Phosphorus content was not correlated with bicarbonate-extractable phosphorus or any other single soil trait. These results suggest that exuded carboxylates increased the availability of phosphorus to the plant, however, the factors that affected root exudation rates are not known. When grown in the same six soils, three commonly used Western Australian chickpea cultivars had very similar rhizosphere carboxylate concentrations (extracted using a 0.2 mM CaCl₂ solution), suggesting that there is little genetic variation for this trait in chickpea. Variation in the concentration of carboxylates in the rhizosphere of white lupin did not parallel that of chickpea across the six soils. However, in both species the proportion of citrate decreased and that of malate increased at lower soil pH. We conclude that patterns of variation in root exudates need to be understood to optimise the use of this trait in enhancing crop phosphorus uptake.     

蚕豆种质资源、抗病育种和QTL定位及抗逆性研究进展

蚕豆是世界温带和亚热带地区一种重要的食用豆类作物,在中国的栽培历史超过2100年。中国是世界上蚕豆栽培面积最大、总产量最多的国家,蚕豆因其高效生物固氮、土壤改良和环境友好特性,已成为中国现代农业种植结构调整、西部经济欠发达地区和丘陵山区农民脱贫致富的重要经济作物。目前,多种DNA标记已广泛应用于大豆、菜豆、豌豆等豆类作物,并取得了一系列重要进展,但蚕豆分子遗传学的研究进展相对缓慢。本文对蚕豆的起源、分类、国内外蚕豆遗传多样性、遗传图谱构建,以及生长习性、抗病育种和QTL定位、抗逆性研究进行了综述,旨在为国内外蚕豆资源的深入研究和利用提供参考。     

Estimation of residual N effect of faba bean and pea on two succeeding cereals using15N methodology

A field experiment was conducted using¹⁵N methodology to study the effect of cultivation of faba bean (Vicia faba L.), pea (Pisum sativum L.) and barley (Hordeum vulgare L.) on the N status of soil and their residual N effect on two succeeding cereals (sorghum (Sorghum vulgare) followed by barley). Faba bean, pea and barley took up 29.6, 34.5 and 53.0 kg N ha^–1 from the soil, but returned to soil through roots only 11.3, 10.8 and 5.7 kg N ha^–1, respectively. Hence, removal of faba bean, pea and barley straw resulted in a N-balance of about –18, –24, and –47 kg ha^–1 respectively. A soil nitrogen conserving effect was observed following the cultivation of faba bean and pea compared to barley which was of the order of 23 and 18 kg N ha^–1, respectively. Cultivation of legumes resulted in a significantly higher A_N value of the soil compared to barley. However, the A_N of the soil following fallow was significantly higher than following legumes, implying that the cultivation of the legumes had depleted the soil less than barley but had not added to the soil N compared to the fallow. The beneficial effect of legume cropping also was reflected in the N yield and dry matter production of the succeeding crops. Cultivation of legumes led to a greater exploitation of soil N by the succeeding crops. Hence, appreciable yield increases observed in the succeeding crops following legumes compared to cereal were due to a N-conserving effect, carry-over of N from the legume residue and to greater uptake of soil N by the succeeding crops when previously cropped to legumes.     

Proteomic characterization of seeds from yellow lupin (Lupinus luteus L.)

Yellow lupin (Lupinus luteus L.) is a legume crop containing a large amount of protein in its seeds. In this study, we constructed a seed‐protein catalog to provide a foundation for further study of the seeds. A total of 736 proteins were identified in 341 2DE spots by nano‐LC‐MS/MS. Eight storage proteins were found as multiple spots in the 2DE gels. The 736 proteins correspond to 152 unique proteins as shown by UniRef50 clustering. Sixty‐seven of the 152 proteins were associated with KEGG‐defined pathways. Of the remaining proteins, 57 were classified according to a GO term. The functions of the remaining 28 proteins have yet to be determined. This is the first yellow lupin seed–protein catalog, and it contains considerably more data than previously reported for white lupin (L. albus L.).     

Exocellular (glyco)proteins of Lupinus albus plants and suspension-cultured cells

Plant species from genus Lupinus are among the oldest known legumes, and various aspects of their biology are considerably different from those commonly observed within Leguminosae. To study this issue in more detail, a suspension culture of Lupinus albus cells was developed, and the glycosylation patterns of exocellular proteins analysed. N-linked oligosaccharide side-chains were detected with two lectins: concanavalin A (ConA) and wheat germ agglutinin (WGA) used with respective anti-lectin antibodies, while O-linked arabinosylated side-chains of (hydroxy)proline-rich glycoproteins were identified with anti-(42 kDa French bean chitin-binding protein) antibodies. The obtained data were compared with analogous ones for exocellular (glyco)proteins from suspension-cultured Phaseolus vulgaris cells and from various tissues of L. albus plants. Major species-specific differences between exocellular (glyco)proteins from lupin and bean cells were identified. Similarly, developmentally regulated glycosylation changes following transition from organised plant tissue to dedifferentiated suspension-cultured lupin cells were detected and analysed.