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1.
Context
In acidic forest soils, aluminium can alter tree health due to its potential toxicity. Aluminium phytotoxicity is mainly influenced by its chemical form and its availability.Methods
As physical-chemical indicators of Al toxicity in soil, Al speciation in soil solutions and in the exchange complex was measured in the rhizosphere and the bulk soil of two tree species (Norway spruce (Picea abies (L.) Karst.) and European Beech (Fagus sylvatica L.) in an acidic soil and in 4 months (November, February, May and August) representing the four seasons in a year.Results
In the bulk soil, Al toxicity was generally higher under Norway spruce than under beech. Furthermore, temporal changes in Al behaviour were identified under Norway spruce but not under beech. The monomeric Al in the soil solutions and the exchangeable Al in the solid soil increased significantly in February under Norway spruce and were positively correlated with nitrate concentration, suggesting that nitrate influence Al speciation and mobility under Norway spruce. In the rhizosphere, Al toxicity was restricted through Al complexation by organic compounds and by nutrient contents independently from the season. The ecological importance of the rhizosphere in Al detoxification is discussed.Conclusions
This study suggests that plant specific differences as well as seasonal changes in plant physiology, microbial activity and microclimatology influence aluminum toxicity in acid forest soils. 相似文献2.
Agnes Rehmus Moritz Bigalke Carlos Valarezo Julio Mora Castillo Wolfgang Wilcke 《Plant and Soil》2014,382(1-2):301-315
Aims
In acid tropical forest soils (pH <5.5) increased mobility of aluminum might limit aboveground productivity. Therefore, we evaluated Al phytotoxicity of three native tree species of tropical montane forests in southern Ecuador.Methods
An hydroponic dose-response experiment was conducted. Seedlings of Cedrela odorata L., Heliocarpus americanus L., and Tabebuia chrysantha (Jacq.) G. Nicholson were treated with 0, 300, 600, 1200, and 2400 μ M Al and an organic layer leachate. Dose-response curves were generated for root and shoot morphologic properties to determine effective concentrations (EC).Results
Shoot biomass and healthy leaf area decreased by 44 % to 83 % at 2400 μ M Al, root biomass did not respond (C. odorata), declined by 51 % (H. americanus), or was stimulated at low Al concentrations of 300 μ M (T. chrysantha). EC10 (i.e. reduction by 10 %) values of Al for total biomass were 315 μ M (C. odorata), 219 μ M (H. americanus), and 368 μ M (T. chrysantha). Helicarpus americanus, a fast growing pioneer tree species, was most sensitive to Al toxicity. Negative effects were strongest if plants grew in organic layer leachate, indicating limitation of plant growth by nutrient scarcity rather than Al toxicity.Conclusions
Al toxicity occurred at Al concentrations far above those in native organic layer leachate. 相似文献3.
Molecular mechanisms of Al tolerance in gramineous plants 总被引:2,自引:0,他引:2
4.
Aluminum tolerance of wheat does not induce changes in dominant bacterial community composition or abundance in an acidic soil 总被引:1,自引:0,他引:1
Chao Wang Xue Qiang Zhao Rong Fu Chen Hai Yan Chu Ren Fang Shen 《Plant and Soil》2013,367(1-2):275-284
Aims
Aluminum-tolerant wheat plants often produce more root exudates such as malate and phosphate than aluminum-sensitive ones under aluminum (Al) stress, which provides environmental differences for microorganism growth in their rhizosphere soils. This study investigated whether soil bacterial community composition and abundance can be affected by wheat plants with different Al tolerance.Methods
Two wheat varieties, Atlas 66 (Al-tolerant) and Scout 66 (Al-sensitive), were grown for 60 days in acidic soils amended with or without CaCO3. Plant growth, soil pH, exchangeable Al content, bacterial community composition and abundance were investigated.Results
Atlas 66 showed better growth and lower rhizosphere soil pH than Scout 66 irrespective of CaCO3 amendment or not, while there was no significant difference in the exchangeable Al content of rhizosphere soil between the two wheat lines. The dominant bacterial community composition and abundance in rhizosphere soils did not differ between Atlas 66 and Scout 66, although the bacterial abundance in rhizosphere soil of both wheat lines was significantly higher than that in bulk soil. Sphingobacteriales, Clostridiales, Burkholderiales and Acidobacteriales were the dominant bacteria phylotypes.Conclusions
The difference in wheat Al tolerance does not induce the changes in the dominant bacterial community composition or abundance in the rhizosphere soils. 相似文献5.
Ageing of zinc in highly-weathered iron-rich soils 总被引:1,自引:0,他引:1
Erica Donner Mike J. McLaughlin Mark E. Hodson Diane Heemsbergen Michael St. J. Warne Stephen Nortcliff Kris Broos 《Plant and Soil》2012,361(1-2):83-95
Background and aims
The reactivity and bioavailability of soluble metal added to soil decreases with time. This process, called ageing, has mainly been investigated in temperate soils. This paper uses isotopic exchangeability to investigate Zn ageing in a range of highly weathered and/or oxide-rich soils.Methods
Changes in lability of soluble added Zn (450?mg Zn/kg soil) over time was measured in six contrasting soils, with pH adjusted to give ten treatments per soil type ranging from pH 4 to 7.Results
Decreasing extractability and isotopic exchangeability (lability) over time revealed substantial fixation of added zinc in six highly weathered/variable charge soils. Strong negative relationships between pH and solubility, and pH and lability were observed. In soils with pH?>?6.5 a significant proportion of the added metal becomes non-isotopically exchangeable within 15?s of addition. Correlations between Mn solubility and Zn lability throughout the incubation demonstrated the role of redox conditions (and pH) in regulating Zn lability.Conclusions
Results showed zinc fixation was strongly related to pH and ageing time, and relatively unaffected by soil type and mineralogy. Very rapid reductions in radiolability immediately (<15?s) after spiking suggest that precipitation plays a role in fixation of added soluble zinc at near neutral pH, however spectroscopic studies are needed to confirm this. Radiolability of added zinc was also affected by changing redox conditions during incubation. 相似文献6.
Distribution and decline of endangered herbaceous heathland species in relation to the chemical composition of the soil 总被引:1,自引:0,他引:1
A. L. F. M. Houdijk P. J. M. Verbeek H. F. G. Van Dijk J. G. M. Roelofs 《Plant and Soil》1993,148(1):137-143
High atmospheric deposition of ammonium affects the physical and chemical status of the soil, increasing nitrogen availability, soil acidity and the mobilization of toxic metal ions. To investigate whether and how the decline of several herbaceous plant species in Dutch heathlands is associated with these processes, the chemical composition of the soil on which these species grow has been compared with the soil on which heathland species such asCalluna vulgaris (L.) Hull,Erica tetralix L. andMolinea caerulea (L.) Moench dominate. The discrimination between both soil types was primarily based on differences in pH (H2O), pH (NaCl) and the aluminium/calcium ratio in the waterextracts. Within the group of endangered herbaceous heathland species these soil parameters also varied. This led to a division into 4 groups of species: Dominating species growing on acid soils Herbaceous species growing together with dominating species on acid soils Herbaceous species growing together with dominating species on moderately acid soils Herbaceous species growing together with dominating species on weakly acid soils. This study indicated that, unlike the decline of heather species, the decline of herbaceous species is not likely to be due to increased competition from grass species as a result of eutrophication. Soil acidification and the changed mineral balance in the soil are most likely to be responsible for the decline of all three groups of herbaceous plant species. ei]R F Huettl 相似文献
u
7.
Background and Aims
Crop residues are important for the redistribution of alkalinity within soils. A net increase in pH following residue addition to soil is typically reported. However, effects are inconsistent in the field due to confounding soil processes and agronomic practises.Methods
A column experiment investigated the effects of canola, chickpea and wheat residues, differing in alkalinity content and C:N ratio, on soil pH changes in a Podosol (Podzol; initial pH 4.5) and Tenosol (Cambisol; initial pH 6.2) under field conditions.Results
Residues (10 g dry matter kg-1 soil; 0–10 cm) increased soil pH, and temporal changes in alkalinity depended on the residue and soil type. Alkalinity was generated via abiotic association reactions between H+ and added organic matter and via ammonification and decarboxylation processes during decomposition. Alkalinity from canola and chickpea residues moved down the soil profile (10–30 cm) and was attributed to nitrate immobilisation and organic anion decomposition by soil microbes.Conclusions
The application of residues to acid and moderately acid soils increased the pH of both topsoil and subsoils, which persisted over 26 months. Maximal increase of pH observed at 3 months was correlated with the concentration of excess cations in the residues. 相似文献8.
Although monomeric Al species are often toxic in acidic soils, the effects of the aluminate ion (Al(OH)
4
−
) on roots grown in alkaline media are still unclear. Dilute, alkaline (pH 9.5) nutrient solutions were used to investigate
the effects of Al(OH)
4
−
on root growth of mungbean (Vigna radiata L.). Root growth was reduced by 13% after 3 d growth in solutions with an Al(OH)
4
−
activity of 16 μM and no detectable polycationic Al (Al13). This decrease in root growth was associated with the formation of lesions on the root tips (due to the rupturing of the
epidermal and outer cortical cells) and a slight limitation to root hair growth (particularly on the lateral roots). When
roots displaying these symptoms were transferred to fresh Al(OH)
4
−
solutions for a further 12 h, no root tip lesions were observed and root hair growth on the lateral roots improved. The symptoms
were similar to those induced by Al13 at concentrations as low as 0.50 μM Al which are below the detection limit of the ferron method. Thus, Al(OH)
4
−
is considered to be non-toxic, with the observed reduction in root growth in solutions containing Al(OH)
4
−
due to the gradual formation of toxic Al13 in the bulk nutrient solution resulting from the acidification of the alkaline nutrient solution by the plant roots. 相似文献
9.
Wenqing Zhang Mónica Calvo-Polanco Z. Chi Chen Janusz J. Zwiazek 《Plant and Soil》2013,373(1-2):775-786
Background and aims
Soil pH is among the major environmental factors affecting plant growth. Although the optimum range of soil pH for growth and the tolerance of pH extremes widely vary among plant species, the pH tolerance mechanisms in plants are still poorly understood. In this study, possible mechanisms were examined to explain the differences in tolerance of boreal plants to root zone pH.Methods
In the controlled-environment solution culture experiments, we compared growth, physiological parameters and tissue nutrient concentrations in aspen, white spruce and tamarack seedlings that were subjected to 8 weeks of root zone pH treatments ranging from 5.0 to 9.0.Results
The pH treatments had little effect on dry weights and net photosynthesis in white spruce seedlings despite reductions in transpiration rates at higher pH levels. In aspen and tamarack, both the growth and physiological parameters significantly decreased at pH higher than 6.0. The chlorosis of young tissues in aspen and tamarack was associated with the reductions in foliar concentrations of several of the examined essential nutrients including Fe and Mn. Although the plants varied in their ability to deliver essential nutrients to growing leaves, there was no direct correlation between tissue nutrient concentrations, chlorophyll concentrations and plant growth. The results also demonstrated strong inhibition of transpiration rates by high pH.Conclusions
The results suggest that high root zone pH can upset water balance in pH sensitive species including aspen. Although the uptake and assimilation of essential elements such as Fe and Mn contribute to plant tolerance of high soil pH, we did not observe a direct relationship between growth and foliar nutrient concentrations to account for the observed differences in growth. 相似文献10.
J. B. Goloran C. R. Chen I. R. Phillips Z. H. Xu L. M. Condron 《Plant and Soil》2014,374(1-2):565-578
Background and aims
Soil phosphorus (P) indices that have been originally developed and applied to agricultural soils for predicting P uptake by plants were examined in a pot experiment to determine the most suitable index for P availability in bauxite-processing residue sand (BRS).Methods
Pot trials with ryegrass were established using BRS that had been amended with various organic (greenwaste compost, biochar and biosolids) and inorganic (zeolite) materials and different levels of di-ammonium phosphate fertiliser. Soil P availability indices tested included anion-exchange membrane (AEM-P), 0.01 M calcium chloride (CaCl2-P), Colwell-P, and Mehlich 3-P.Results
AEM-P was found to most closely reflect the available P status in BRS across all treatments, and had the strongest associations with plant P uptake compared to Colwell-P, Mehlich 3-P and CaCl2-P. AEM-P was more closely correlated with P uptake by ryegrass than other P indices, while Colwell-P was closely related to leaf dry matter. Interestingly, a strong inverse relationship between plant indices and pH in BRS growth media was observed, and an adequate level of plant P uptake was found only in 15 year-old rehabilitated BRS with pH <?8.0.Conclusions
AEM-P was found to be the most suitable index for evaluating P availability in highly alkaline BRS and pH was an important parameter affecting uptake of P by ryegrass. Importantly, time is required (> 5 years) before improved uptake of P by plants can be observed in rehabilitated residue sand embankments. 相似文献11.
David Solance Smith Jennifer A. Schweitzer Philip Turk Joseph K. Bailey Stephen C. Hart Stephen M. Shuster Thomas G. Whitham 《Plant and Soil》2012,352(1-2):243-251
Background and aims
Soils can act as agents of natural selection, causing differential fitness among genotypes and/or families of the same plant species, especially when soils have extreme physical or chemical properties. More subtle changes in soils, such as variation in microbial communities, may also act as agents of selection. We hypothesized that variation in soil properties within a single river drainage can be a selective gradient, driving local adaptation in plants.Methods
Using seeds collected from individual genotypes of Populus angustifolia James and soils collected from underneath the same trees, we use a reciprocal transplant design to test whether seedlings would be locally adapted to their parental soil type.Results
We found three patterns: 1. Soils from beneath individual genotypes varied in pH, soil texture, nutrient content, microbial biomass and the physiological status of microorganisms. 2. Seedlings grown in local soils experienced 2.5-fold greater survival than seedlings planted in non-local soils. 3. Using a composite of height, number of leaves and leaf area to measure plant growth, seedlings grew ~17.5% larger in their local soil than in non-local soil.Conclusions
These data support the hypothesis that variation in soils across subtle gradients can act as an important selective agent, causing differential fitness and local adaptation in plants. 相似文献12.
T. E. Smith S. R. Grattan C. M. Grieve J. A. Poss A. E. Läuchli D. L. Suarez 《Plant and Soil》2013,370(1-2):541-554
Aims
Soil pH is known to influence many important biochemical processes in plants and soils, however its role in salinity—boron interactions affecting plant growth and ion relations has not been examined. The purpose of this research was to evaluate the interactive effects of salinity, boron and soil solution pH on broccoli (Brassica oleracea L.) growth, yield, consumptive water use and shoot-boron accumulation.Methods
A greenhouse experiment was conducted using a sand tank system where salinity-B-pH treatment solutions were supplemented with a complete nutrient solution. Sulfate-dominated irrigation waters, characteristic of groundwater in California’s San Joaquin valley (SJV), were tested at EC levels of 2, 5, 8, 11 and 14 dS?m?1. Each salinity treatment consisted of two boron treatments (0.5 and 21 mg?L?1) and each of those treatments was tested under slightly basic (pH?8.0) and slightly acidic (pH?6.0) conditions.Results
Results included multiple salinity-boron-pH interactions affecting shoot biomass, head yield and consumptive water use. Broccoli fresh head yields were significantly reduced by salinity and boron, but the degree of yield reductions was influenced by pH. Relative head yields were substantially reduced in treatments with high pH and high B, particularly under low and high salinity where head yields were decreased by 89 % and 96 %, respectively, relative to those at low salinity and low boron. Intermediate levels of salinity were far less damaging. Increased salinity and boron reduced evapotranspiration (ET) and there were no salinity-boron associated interactions on ET. However, increased salinity and boron concentrations increased water use efficiency (shoot biomass/cumulative volume ET). Shoot B concentration increased with increased boron and was greater at pH?6 as compared to pH?8. Shoot boron concentration decreased with increasing salinity at both pH levels but particularly at the high substrate boron concentration.Conclusions
It is likely that different mechanisms, yet unknown, are responsible for severe head-yield reductions at low and high salinity in the presence of high boron under alkaline conditions. We found that boron in the shoot did not accumulate by a simple passive process. Rather as boron increased from 0.5 to 21 mg?L?1, there was a restrictive mechanism where total shoot boron (mg plant?1) was reduced by 10 to 40 times the amount potentially supplied to the shoot by passive transport via mass flow perhaps involving complex interactions with membrane channels and B exporters. Total shoot boron concentration was a poor indicator of plant growth response. 相似文献13.
Background and aims
Aluminum (Al) accumulator plants are occasionally found in certain genera or families of woody plant species that are broadly dispersed in the angiosperm phylogeny. However, spatial and seasonal patterns in Al accumulation within the closely related species of each group remain poorly understood.Methods
We quantitatively monitored the internal Al levels of eight Theaceae and Ternstroemiaceae species growing on acidic soils at multiple sites.Results
Among the eight species, seven other than Ternstroemia gymnanthera shared a rapid Al accumulation in the developing leaves. Species comparison revealed that Al accumulation in mature leaves saturates within a flushing year, regardless of differences in leaf structure, seasonality, and acidic soil pH (4.5–5.5) at multiple sites. In tall trees of Stewartia monadelpha, the Al contents of the leaves were constantly high irrespective of their height positions up to 12 m. Moreover, the Al content of the leaves was only slightly decreased in the last 2 weeks of autumn senescence, in which nitrogen (N) or phosphate (P) retranslocation had been completed.Conclusion
These results suggest that most of the Theaceae and Ternstroemiaceae species possess an effective metal-transport mechanism that rapidly loads Al into the young leaves until each level reaches a species-specific threshold.14.
Background
Aluminium (Al) toxicity and drought stress are two major constraints for crop production in the world, particularly in the tropics. The variation in rainfall distribution and longer dry spells in much of the tropics during the main growing period of crops are becoming increasingly important yield-limiting factors with the global climate change. As a result, crop genotypes that are tolerant of both drought and Al toxicity need to be developed.Scope
The present review mainly focuses on the interaction of Al and drought on root development, crop growth and yield on acid soils. It summarizes evidence from our own studies and other published/related work, and provides novel insights into the breeding for the adaptation to these combined abiotic stresses. The primary symptom of Al phytotoxicity is the inhibition of root growth. The impeded root system will restrict the roots for exploring the acid subsoil to absorb water and nutrients which is particularly important under condition of low soil moisture in the surface soil under drought. Whereas drought primarily affects shoot growth, effects of phytotoxic Al on shoot growth are mostly secondary effects that are induced by Al affecting root growth and function, while under drought stress root growth may even be promoted. Much progress has recently been made in the understanding of the physiology and molecular biology of the interaction between Al toxicity and drought stress in common bean (Phaseolus vulgaris L.) in hydroponics and in an Al-toxic soil.Conclusions
Crops growing on acid soils yield less than their potential because of the poorly developed root system that limits nutrient and water uptake. Breeding for drought resistance must be combined with Al resistance, to assure that drought resistance is expressed adequately in crops grown on soils with acid Al-toxic subsoils. 相似文献15.
Stanislava Vondráčková Michal Hejcman Jiřina Száková Vladimíra Müllerová Pavel Tlustoš 《Plant and Soil》2014,379(1-2):231-245
Background and aims
The ionome (elemental composition) of grassland species has rarely been studied at the level of individual organs and little is known about effects of soil chemical properties on the ionome. Using the model oxalate plant Rumex obtusifolius, we asked how its biomass production and the distribution of elements between its organs is affected by soil chemical properties.Methods
We established a pot experiment with R. obtusifolius planted in acidic non-contaminated control and in slightly acidic and alkaline soils anthropogenically contaminated by the risk elements As, Cd, Pb, and Zn. Both contaminated soils were untreated and treated by lime and superphosphate. We determined biomass production and the concentrations of elements in its organs.Results
Biomass production was negatively related to the mobility of micro- and risk elements. Restricted transport of micro- and risk elements from belowground organs into leaves was recorded in untreated contaminated soils. In both lime-treated soils and in superphosphate-treated alkaline soil, elevated transport of micro- and risk elements from belowground organs into leaves was recorded in comparison to untreated contaminated soils. The lowest concentrations of micro- and risk elements were recorded in stems and seeds, followed by belowground organs and leaves.Conclusions
R. obtusifolius is an As-, Cd-, Pb-, and Zn-excluder and is sensitive to high availability of micro- and risk elements in the soil. Soil chemical properties affect the distribution of essential elements within the plant greatly. 相似文献16.
Aims
Some rhizobia can convert insoluble P into available forms for plant growth but the underlying mechanisms for this are not understood. In this study, the function of rhizobia in P acquisition from P sources for soybean was studied.Methods
Four rhizobial strains were employed to evaluate their phosphate-solubilizing (PS) activity, their ability to mediate pH changes in growth medium for different P sources, and IAA production. A sand culture experiment using different P sources was carried out to characterize P acquisition changes of soybean plants with or without rhizobium inoculation. Rhizospheric acidification in soybean was further analyzed in hydroponics.Results
Our results showed that all the tested rhizobial strains exhibited significant PS activity for different P sources in the order of Ca-P>Al-P>Phy-P??Fe-P as indicated by the halo/colony ratio technique and increased Pi percentage in the solid and liquid phases, respectively. Furthermore, all of the rhizobial strains could acidify the growth medium for all P sources except Phy-P, but only three of them produced IAA. Compared to non-nodulated plants, the nodulated plants had greater plant biomass and P content in sand culture for all the tested P sources, especially for Ca-P. Moreover, H+ and total acid exudation was more significantly enhanced in the nodulated plants in hydroponics.Conclusions
Our results suggested that the PS ability of rhizobia is more related to acidification of the growth medium than IAA production. Rhizobium inoculation could enhance P acquisition in soybean, especially on soils where Ca-P is the primary P source, and the primary mechanism for rhizobial-mediated P solubilization appears to be via Pi remobilization of nodulated roots through rhizospheric acidification. 相似文献17.
Monica Calvo-Polanco Wenqing Zhang S. Ellen Macdonald Jorge Señorans Janusz J. Zwiazek 《Plant and Soil》2017,420(1-2):195-208
Aims
Reclamation following oil sands mining in northeastern Alberta (Canada) creates adverse reforestation soil conditions, including extreme pH values. We elucidated pH tolerance limits of boreal plant species and how pH affects nutrient uptake in these plants.Methods
We measured growth, gas exchange, and foliar nutrient concentration of 15 common northern boreal forest plants after eight weeks exposure to root zone pH ranging from 5.0 to 9.0. Cluster analyses were used to group these species based on their pH responses.Results
Based on their growth and gas exchange responses to pH, the 15 plant species could be divided into five groups, each of which contained species that commonly co-occur in particular boreal forest site types. For the foliar nutrient responses to pH, the 15 species could be grouped into only two categories; both showed decreases in foliar N, P, Fe and Zn concentration with increasing pH, with a more pronounced effect on the group that included trembling aspen, paper birch and chokecherry.Conclusions
The evidence of differential adaptation to pH by habitat type suggests the importance of soil pH as a factor affecting boreal plant species distribution and could be helpful for selection of species suitable for reclamation of sites with altered soil pH.18.
Pilar Castro-Díez Natalia Fierro-Brunnenmeister Noelia González-Mu?oz Antonio Gallardo 《Plant and Soil》2012,350(1-2):179-191
Aims
We assessed the effects of native and exotic tree leaf litter on soil properties in two contrasting scenarios. The native Quercus robur and Pinus pinaster tree species coexist with the aliens Eucalyptus globulus and Acacia dealbata in acid soils of NW Spain. The native trees Fraxinus angustifolia and Ulmus minor coexist with the aliens Ailanthus altissima, Robinia pseudoacacia and Ulmus pumila in eutrophic basic riparian soils in Central Spain.Methods
Four plastic trays per species were filled with homogenized top-soil of the site and covered with leaf litter. Before and after 9?months of incubation, litter mass, soil pH, organic matter, mineral and total N were measured. Available mineral N (NO 3 ? -N and NH 4 + -N) was assessed every 2?months.Results
Soil biological activity was higher in the basic than in the acid soil. Litter of the exotic trees tended to decompose less than litter of native species, probably due to the presence of secondary metabolites in the former. Soil pH, mineral and total N responded differently to different litter types, irrespective of their exotic or native origin (acid soil), or was similar across litter treatments (basic riparian soil). The similar response of the basic soil to the addition of different litter types may be due to the low contrast of litter quality between the species. E. globulus litter inhibitied soil microbial activity much more than the rest of the studied litter types, leading to a drastic impoverishment of N in soils.Conclusion
Litter of exotic N-fixing trees (A. dealbata and R. pseudoacacia) did not increase soil N pools because of the inhibition of microbial activity by secondary compounds. Therefore, secondary metabolites of the litter played a major role explaining exotic litter impact on soil properties. 相似文献19.
Background and aims
Embothrium coccineum (R. et J. Forst.) is a Proteaceae species from the southern part of South America. South-central Chilean soils are younger and contain more phosphorus (P) than soils in Australia and South Africa, where Proteaceae are common. Phosphorus deficiency is the main factor promoting cluster-root formation in Proteaceae. It is not known, however, whether this also applies to E. coccineum, which grows on soils with higher P content.Methods
Four-month-old seedlings were grown for 4 weeks in hydroponic cultures with 1 μM P or 50 μM P. The number of cluster roots, relative height increment, biomass distribution, cluster root/total root biomass ratio, foliar P concentration, root acid phosphatase activity and root carboxylate-exudation rates were determined.Results
Seedlings growing at 50 μM P showed a 10?, 1.3? and 3.3-fold greater increase in relative height, total dry mass and foliar P concentration, respectively, compared with those grown at1 μM P. However, seedlings grown at 1 μM P showed a 5?, 16?, 1.7? and 1.3-fold greater number of cluster roots, cluster root/total root biomass ratio, phosphatase activity and total carboxylate exudation, respectively, as compared with those grown at 50 μM P.Conclusions
A low P supply promotes the initiation, growth and metabolic activity of cluster roots which is in accordance with reports on Proteaceae species occurring in ancient and highly weathered soils. 相似文献20.
Steve P. McGrath Brian J. Chambers Matthew J. Taylor Colin H. Carlton-Smith 《Plant and Soil》2012,361(1-2):97-108