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1.
The relationship between root-hair growth, acid exudation and phosphorus (P) uptake as well as the quantitative trait loci (QTLs) associated with these traits were determined for a recombinant inbred line (RIL) population derived from the cross of two contrasting common bean (Phaseolus vulgaris L.) genotypes, DOR364 and G19833, which were grown in solution culture and under field conditions with low-P availability. In the solution-culture study, root-hair density, root-hair length, H+ exudation and total acid exudation were measured. Substantial genotypic variability was observed for these traits and their response to P availability. The P-efficient parent G19833 had greater root-hair density, longer root-hair length, and greater exudation of H+ and total acid than the P-inefficient genotype DOR364. These traits segregated continuously in the RIL population, with obvious tendency of trait transgression. Genetic analysis revealed that the root traits measured had various heritabilities, with h b 2 ranging from 43.24 to 86.70%. Using an integrated genetic map developed for the population, a total of 19 QTLs associated with root hair, acid exudation and P-uptake traits were detected on 8 linkage groups. P uptake in the field was positively correlated with total acid exudation, basal root-hair length, and basal root-hair density. Acid-exudation traits were intercorrelated, as were root-hair traits. Total acid exudation was positively correlated with basal root-hair density and length. Linkage analysis revealed that some of the root-trait QTLs were closely linked with QTLs for P uptake in the field. We propose that marker-assisted selection (MAS) might be a feasible alternative to conventional screening of phenotypic root traits.  相似文献   

2.
Effect of phosphorus availability on basal root shallowness in common bean   总被引:25,自引:2,他引:25  
Liao  Hong  Rubio  Gerardo  Yan  Xiaolong  Cao  Aiqin  Brown  Kathleen M.  Lynch  Jonathan P. 《Plant and Soil》2001,232(1-2):69-79
Root gravitropism may be an important element of plant response to phosphorus availability because it determines root foraging in fertile topsoil horizons, and thereby phosphorus acquisition. In this study we seek to test this hypothesis in both two dimensional paper growth pouch and three-dimensional solid media of sand and soil cultures. Five common bean (Phaseolus vulgaris L.) genotypes with contrasting adaptation to low phosphorus availability were evaluated in growth pouches over 6 days of growth, and in sand culture and soil culture over 4 weeks of growth. In all three media, phosphorus availability regulated the gravitropic response of basal roots in a genotype-dependent manner. In pouches, sand, and soil, the phosphorus-inefficient genotype DOR 364 had deeper roots with phosphorus stress, whereas the phosphorus-efficient genotype G19833 responded to phosphorus stress by producing shallower roots. Genotypes were most responsive to phosphorus stress in sand culture, where relative root allocation to the 0–3- and 3–6-cm horizons increased 50% with phosphorus stress, and varied 300% (3–6 cm) to 500% (0–3 cm) among genotypes. Our results indicate that (1) phosphorus availability regulates root gravitropic growth in both paper and solid media, (2) responses observed in young seedlings continue throughout vegetative growth, (3) the response of root gravitropism to phosphorus availability varies among genotypes, and (4) genotypic adaptation to low phosphorus availability is correlated with the ability to allocate roots to shallow soil horizons under phosphorus stress.  相似文献   

3.
Vale FR  Jackson WA  Volk RJ 《Plant physiology》1987,84(4):1416-1420
Potassium influx into roots of dark-grown decapitated maize seedling (Zea mays L., cv Pioneer 3369A) was examined in presence and absence of ambient ammonium and at various root potassium concentrations. Six-day old seedlings which were dependent on the endosperm reserves for their energy source were exposed to KCl (labeled with 86Rb) ranging from 5 to 200 micromolar. At both low (13 micromoles per gram fresh weight) and high (100 micromoles per gram fresh weight) root potassium concentration, isotherms indicated two potassium influx systems, one approaching saturation at 50 to 100 micromolar potassium and an additional one tentatively considered to be linear. A mixed-type inhibition by ammonium for the low-concentration saturable system was indicated by a concomitant decrease in Vmax and increase in Km. High root potassium concentration decreased Vmax but had little effect on Km of this system. The rate constant for the second quasilinear system was decreased by ambient ammonium and by high root potassium status. Transfer of high potassium roots to potassium-free solutions resulted in an increase in influx within 2 hours; by 24 hours influx significantly exceeded that of roots not previously exposed to potassium. In roots of both low and high root potassium concentrations, potassium influx was restricted progressively as ambient ammonium increased to about 100 micromolar, but there was little further inhibition as ammonium concentrations increased beyond that to 500 micromolar. The data imply that potassium influx has two components, one subject to inhibition by ambient ammonium and one relatively resistant.  相似文献   

4.
Interspecific root/rhizosphere interactions affect phosphorus (P) uptake and the productivity of maize/faba bean and maize/wheat intercropping systems. The aim of these experiments was to determine whether manipulation of maize root growth could improve the productivity of the two intercropping systems. Two near isogenic maize hybrids (the larger-rooted T149 and smaller-rooted T222) were intercropped with faba bean and wheat, under conditions of high- and low-P availability. The larger-rooted T149 showed greater competitive ability than the smaller-rooted T222 in both maize/faba bean and maize/wheat intercropping systems. The higher competitive ability of T149 improved the productivity of the maize/faba bean intercropping system in P-sufficient conditions. In maize/wheat intercropping systems, root growth, shoot biomass, and P uptake of maize were inhibited by wheat, regardless of the P-supply. Compared with T222, the larger-rooted T149 suffered less in the intercropping systems. The total biomass of the maize/wheat intercropping system was higher for wheat/T149 than for wheat/T222 under low-P conditions. These data suggested that genetic improvement of maize root size could enhance maize growth and its ability to compete for P resources in maize/faba bean and maize/wheat intercropping systems. In addition, depending on the P availability, larger maize roots could increase the productivity of intercropping systems.  相似文献   

5.
Nielsen  Kai L.  Miller  Carter R.  Beck  Douglas  Lynch  Jonathan P. 《Plant and Soil》1999,206(2):181-190
Root growth and architecture are important for phosphorus acquisition due to the relative immobility of P in the soil. Fractal geometry is a potential new approach to the analysis of root architecture. Substantial genetic variation in root growth and architecture has been observed in common bean. Common bean (Phaseolus vulgaris L.) genotypes with contrasting root architecture were grown under moderate and low P conditions in a field experiment. Linear and planar fractal dimension were measured by tracing root intercepts with vertical planes. Linear fractal dimension increased over time in efficient genotypes, but remained fairly constant over time in inefficient genotypes. Planar fractal dimension increased over time for all genotypes, but was higher in efficient than inefficient genotypes at the end of the experiment. Planar fractal dimension of medium P plants was found to correlate with shoot P content indicating fractal dimension to be a possible indicator for root P uptake. The increasing fractal dimension over time indicates that fractal analysis is a sensitive measure of root branching intensity. A less destructive method for acquisition of data that allows for continuous analysis of fractal geometry and thereby screening for more P efficient genotypes in the field is suggested. This method will allow the researcher to conduct fractal analysis and still complete field trials with final yield evaluation.  相似文献   

6.
An obstacle to the study of root architecture is the difficulty of measuring and quantifying the three-dimensional configuration of roots in soil. The objective of this work was to determine if fractal geometry might be useful in estimating the three-dimensional complexity of root architecture from more accessible measurements. A set of results called projection theorems predict that the fractal dimension (FD) of a projection of a root system should be identical to the FD of roots in three-dimensional space (three-dimensional FD). To test this prediction we employed SimRoot, an explicit geometric simulation model of root growth derived from empirical measurements of common bean (Phaseolus vulgaris L.). We computed the three-dimensional FD, FD of horizontal plane intercepts (planar FD), FD of vertical line intercepts (linear FD), and FD of orthogonal projections onto planes (projected FD). Three-dimensional FD was found to differ from corresponding projected FD, suggesting that the analysis of roots grown in a narrow space or excavated and flattened prior to analysis is problematic. A log-linear relationship was found between FD of roots and spatial dimension. This log-linear relationship suggests that the three-dimensional FD of root systems may be accurately estimated from excavations and tracing of root intersections on exposed planes.  相似文献   

7.
When the roots of Vicia faba L. beans were subjected to hypoxic stress, the activity of H+-ATPase on the peribacteroid membrane, as well as the transport of dicarboxylates (malate and succinate) mediated by this enzyme, decreased. Since malate and succinate are the main carbon-containing metabolites involved in the energy supply to bacteroids, this caused a change of the relation type from mutualism to commensalism, and the domination of the eukaryotes over the prokaryotes consequently increased.  相似文献   

8.
The use of kinetic equations of NO3- transport systems in oilseed rape (Brassica napus), determined by 15NO3- labeling under controlled conditions, combined with experimental field data from the INRA-Chalons rape database were used to model NO3- uptake during the plant growth cycle. The quantitative effects of different factors such as day/night cycle, ontogenetic stages, root temperature, photosynthetically active radiation, and soil nitrate availability on different components of the constitutive high-affinity transport systems, constitutive low-affinity transport systems, inducible low-affinity transport systems, and inducible high-affinity transport systems of nitrate were then determined to improve the model's predictions. Simulated uptake correlated well with measured values of nitrogen (N) uptake under field conditions for all N fertilization rates tested. Model outputs showed that the high-affinity transport system accounted for about 89% of total NO3- uptake (18% and 71% for constitutive high-affinity transport systems and inducible high-affinity transport systems, respectively) when no fertilizer was applied. The low-affinity transport system accounted for a minor proportion of total N uptake, and its activity was restricted to the early phase of the growth cycle. However, N fertilization in spring increased the duration of its contribution to total N uptake. Overall, data show that this mechanistic and environmentally regulated approach is a powerful means to simulate total N uptake in the field with the advantage of taking both physiologically regulated processes at the overall plant level and specific nitrate transport system characteristics into account.  相似文献   

9.
10.
The influence of varied supply of phosphorus (10 and 250 mmolP m–3) potassium (50 and 2010 mmol K m–3) and magnesium(20 and 1000 mmol Mg m–3) on the partitioning of dry matterand carbohydrates (reducing sugars, sucrose and starch) betweenshoots and roots was studied in bean (Phaseolus vulgaris) plantsgrown in nutrient solution over a 12 d period. Shoot and rootgrowth were quite differently affected by low supply of P, K,and Mg. The shoot/root dry weight ratios were 4.9 in the control(sufficient plants), 1.8 in P-deficient, 6.9 in K-deficientand 10.2 in Mg-deficient plants. In primary (source) leaves,but not in trifoliate leaves, concentrations of reducing sugars,sucrose and starch were also differently affected by low nutrientsupply. In primary leaves under K deficiency and, particularlyMg deficiency, the concentrations of sucrose and reducing sugarswere much higher than in control and P-deficient plants. Magnesiumdeficiency also distinctly increased the starch concentrationin the primary leaves. In contrast, in roots, the lowest concenfrationsof sucrose, reducing sugars and starch were found in Mg-deficientplants, whereas the concentrations of sucrose and starch wereparticularly high in P-deficient plants. There was a close relationshipbetween shoot/root dry weight ratios and relative distributionof total carbohydrates (sugars and starch) in shoot and roots.Of the total amounts of carbohyd rates per plant, the followingproportions were parti tioned to the roots: 22.7% in P-deficient,15.7% in control, 3.4% in K-deficient and 0.8% in Mg-deficientplants. The results indicate a distinct role of Mg and K in the exportof photosynthates from leaves to roots and suggest that alterationin photosynthate partitioning plays a major role in the differencesin dry matter distribution between shoots and roots of plantssuffering from mineral nutrient deficiency. Key words: Bean, carbohydrates, magnesium nutrition, phosphorus nutrition, potassium nutrition, shoot/root growth  相似文献   

11.
12.
13.
14.

Background

Native starch accumulates as granules containing two glucose polymers: amylose and amylopectin. Phosphate (0.2–0.5%) and proteins (0.1–0.7%) are also present in some starches. Phosphate groups play a major role in starch metabolism while granule-bound starch synthase 1 (GBSS1) which represents up to 95% of the proteins bound to the granule is responsible for amylose biosynthesis.

Methods

Synchrotron micro-X-ray fluorescence (μXRF) was used for the first time for high-resolution mapping of GBSS1 and phosphate groups based on the XRF signal of sulfur (S) and phosphorus (P), respectively. Wild-type starches were studied as well as their related mutants lacking GBSS1 or starch-phosphorylating enzyme.

Results

Wild-type potato and maize starch exhibited high level of phosphorylation and high content of sulfur respectively when compared to mutant potato starch lacking glucan water dikinase (GWD) and mutant maize starch lacking GBSS1. Phosphate groups are mostly present at the periphery of wild-type potato starch granules, and spread all over the granule in the amylose-free mutant. P and S XRF were also measured within single small starch granules from Arabidopsis or Chlamydomonas not exceeding 3–5 μm in diameter.

Conclusions

Imaging GBSS1 (by S mapping) in potato starch sections showed that the antisense technique suppresses the expression of GBSS1 during biosynthesis. P mapping confirmed that amylose is mostly present in the center of the granule, which had been suggested before.

General significance

μXRF is a potentially powerful technique to analyze the minor constituents of starch and understand starch structure/properties or biosynthesis by the use of selected genetic backgrounds.  相似文献   

15.
16.
Summary This paper provides some quantitative data on the relationship between the rate of uptake of phosphorus and potassium from soil and the amount of root, root density and rate of root growth. Three experiments were conducted with winter wheat, all grown in the same soil. Root growth and density were manipulated in three ways: (1) by root pruning; (2) by a split-root technique; (3) by growing plants in different soil volumes. Root lengths as well as weights were determined.Potassium uptake per unit amount of root was generally lower the higher the root density, suggesting that roots were competing with each other for potassium even at the lowest density. In contrast, phosphorus uptake showed a good correlation with root growth irrespective of root density or plant age. Phosphorus uptake during a period was more closely and consistently correlated with root growth during that period than with the total amount of root on the plant. The results can be explained in terms of ion supply to the root surface, taking into account the diffusion coefficients of the ions and the approximate distances between neighbouring roots.Now Mrs. Watkins; address 39 Leach Heath Lane, Rubery, Birmingham.Now Mrs. Watkins; address 39 Leach Heath Lane, Rubery, Birmingham.  相似文献   

17.
Promotion of root elongation by phosphorus deficiency   总被引:12,自引:0,他引:12  
Decrease of culture solution pH and increase in cation/anion ratio in the plant were observed when horsegram (Macrotyloma uniflorum (Lam.) Verdc.) was grown in solution culture deficient in phosphorus. The effux of H+ from the roots of –P plants was observed in bromocresol purple agar. The length of root cells was considerably increased by –P treatment. Thus a close correlation between H+ excretion, length of the root cells and root elongation in response to P deficiency was established.  相似文献   

18.
The initial response of plants to aluminium (Al) is an inhibition of root elongation. In the present study, short and medium-term effects of Al treatment (20 muM) on root growth and Al accumulation of two common bean (Phaseolus vulgaris L.) genotypes, VAX-1 (Al-sensitive) and Quimbaya (Al-resistant), were studied. Root elongation of both genotypes was severely inhibited during the first 3-4 h of Al treatment. Thereafter, both genotypes showed gradual recovery. However, this recovery continued in genotype Quimbaya until the root elongation rate reached the level of the control (without Al) while the genotype VAX-1 was increasingly damaged by Al after 12 h of Al treatment. Short-term Al treatment (90 microM Al) to different zones of the root apex using agarose blocks corroborated the importance of the transition zone (TZ, 1-2 mm) as a main target of Al. However, Al applied to the elongation zone (EZ) also contributed to the overall inhibition of root elongation. Enhanced inhibition of root elongation during the initial 4 h of Al treatment was related to high Al accumulation in root apices in both genotypes (Quimbaya>VAX-1). Recovery from Al stress was reflected by decreasing Al contents especially in the TZ, but also in the EZ. After 24 h of Al treatment the high Al resistance of Quimbaya was reflected by much lower Al contents in the entire root apex. The results confirmed that genotypic differences in Al resistance in common bean are built up during medium-term exposure of the roots to Al. For this acquisition of Al resistance, the activation and maintenance of an Al exclusion mechanism, especially in the TZ but also in the EZ, appears to be decisive.  相似文献   

19.
20.
Changes in penguin abundance and distribution can be used to understand the response of species to climate change and fisheries pressures, and as a gauge of ecosystem health. Traditionally, population estimates have involved direct counts, but remote sensing and digital mapping methodologies can provide us with alternative techniques for assessing the size and distribution of penguin populations. Here, we demonstrate the use of a field-based digital mapping system (DMS), combining a handheld geographic information system with integrated geographical positioning system as a method for: (a) assessing penguin colony area and (b) ground-truthing colony area as derived from satellite imagery. Work took place at Signy Island, South Orkneys, where colonies of the three congeneric pygoscelid penguins: Adélie Pygoscelis adeliae, chinstrap P. antarctica and gentoo P. papua were surveyed. Colony areas were derived by mapping colony boundaries using the DMS with visual counts of the number of nesting birds made concurrently. Area was found to be a good predictor for number of nests for all three species of penguin. Using a maximum likelihood multivariate classification of remotely sensed satellite imagery (QuickBird2, 18 January 2010; Digital Globe ID: 01001000B90AD00), we were able to identify penguin colonies from the spectral signature of guano and differentiate between colonies of Adélie and chinstrap penguins. The area classified (all species combined) from satellite imagery versus area from DMS data was closely related (R 2 = 0.88). Combining these techniques gives a simple and transferrable methodology for examining penguin distribution and abundance at local and regional scales.  相似文献   

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