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1.
The mechanism of Al uptake in melastoma (Melastoma malabathricum L.), which accumulates Al in excess of 10 000 mg kg–1 in its leaves and roots, was investigated. Al uptake kinetics in excised melastoma roots showed a biphasic pattern, with an initial rapid phase followed by a slow phase. It was indicated that Al uptake in the excised roots occurs mostly through passive accumulation in the apoplast. On the other hand, Al uptake rate in roots of whole melastoma plant was almost double that in excised roots. The difference of Al uptake rate between excised roots and whole plant seems to be due to transpiration-depended Al uptake. Results from a long-term experiment showed that different characteristics of Al accumulation between melastoma and barley was caused by the difference in capacity to retain Al in root symplast, rather than by the difference in uptake rate into symplast. Concentrations of oxalate in root symplastic and apoplastic fractions, and total oxalate in shoots and roots, did not change greatly with time of Al exposure compared to Al concentration, although oxalate is considered as a main Al ligand in tissue of melastoma. On the other hand, oxalate exudation to root apoplast was induced within 24 h of Al exposure; the role of such exudation was discussed. 相似文献
2.
Form of aluminium for uptake and translocation in buckwheat (Fagopyrum esculentum Moench) 总被引:5,自引:0,他引:5
The forms of Al for uptake by the roots and translocation from the root to the shoot were investigated in a buckwheat (Fagopyrum esculentum Moench, cv. Jianxi) that accumulates Al in its leaves. The Al concentration in the xylem sap was 15-fold higher in the plants
exposed to AlCl3 than in those exposed to an Al-oxalate (1:3) complex, suggesting that the roots take up Al in the ionic form. The Al concentration
in the xylem sap was 4-fold higher than that in the external solution after a 1-h exposure to AlCl3 solution and 10-fold higher after a 2-h exposure. The Al concentration in the xylem sap increased with increasing Al concentration
in the external solution. The Al uptake was not affected by a respiratory inhibitor, hydroxylamine, but significantly inhibited
by the addition of La. These results suggest that Al uptake by the root is a passive process, and La3+ competes for the binding sites for Al3+ on the plasma membrane. The form of Al in the xylem sap was identified by 27Al-nuclear magnetic resonance analysis. The chemical shift of 27Al in the xylem sap was around 10.9 ppm, which is consistent with that of the Al-citrate complex. Furthermore, the dominant
organic acid in the xylem sap was citric acid, indicating that Al was translocated in the form of Al-citrate complex. Because
Al is present as Al-oxalate (1:3) in the root, the present data show that ligand exchange from oxalate to citrate occurs before
Al is released to xylem.
Received: 10 December 1999 / Accepted: 3 February 2000 相似文献
3.
Hideaki Matsumoto Yasushi Senoo Minobu Kasai Masayoshi Maeshima 《Journal of plant research》1996,109(1):99-105
Pea root elongation was strongly inhibited in the presence of a low concentration of Al (5 μM). In Al-treated root, the epidermis
was markedly injured and characterized by an irregular layer of cells of the root surface. Approximately 30% of total absorbed
Al accumulated in the root tip and Al therein was found to cause the inhibition of whole root elongation. Increasing concentrations
of Ca2+ effectively ameliorated the inhibition of root elongation by Al and 1 mM of CaCl2 completely repressed the inhibition of root elongation by 50 μM Al. The ameliorating effect of Ca2+ was due to the reduction of Al uptake.
H+-ATPase and H+-PPase activity as well as ATP and PPidependent H+ transport activity of vacuolar membrane vesicles prepared from barley roots increased to a similar extent by the treatment
with 50 μM AlCl3. The rate of increase of the amount of H+-ATPase and H+-PPase was proportional to that of protein content measured by immunoblot analysis with antibodies against the catalytic subunit
of the vacuolar H+-ATPase and H+-PPase of mung bean. The increase of both activities was discussed in relation to the physiological tolerance mechanism of
barley root against Al stress. 相似文献
4.
The relationship between root Al concentrations and Al fractions in the soil solution was examined in a mature Abies amabilis ecosystem in the Cascade Range of Washington State. The naturally acidic soils in these ecosystems lead to high concentrations of aqueous Al in soil solutions and contribute to the biocycling of Al by the A. amabilis/T. mertensiana stand. Root concentrations of Al were very closely related to aqueous Al3+ activities, but poorly correlated with total aqueous Al concentrations. The solution Al/Ca molar ratios followed a seasonal cycle with low values during the fall and high values during the spring. Ratios remained <1 throughout the year in the Oa horizon while they varied between 2 and 14 in the E and Bhs horizons. The vertical distribution of roots and the mortality of fine roots may be linked to the soil solution Al/Ca ratio. Root cation exchange capacity ranged between 180 and 225 mol g-1 and the exchangeable Al fraction represented from 12–17% of the total Al content in the root. Evidence for solid-phase co-precipitates of Al with PO4 and oxalate was indicated from selective dissolution of the root tissue. Sufficient quantities of PO4 and oxalate exist in the roots to tie up 20–40% of the Al present in the roots of the Oa and E horizons, but only 9% of that present in the Bhs horizon. Species differences in the distribution of Al between the above-ground and below-ground components may be dictated by these retention processes in the fine roots. 相似文献
5.
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
6.
Dennis B. Lazof Magaly Rincón Thomas W. Rufty Charles T. Mackown Thomas E. Carter 《Plant and Soil》1994,164(2):291-297
A study was conducted to examine aluminum (Al) exclusion by roots of two differentially tolerant soybean (Glycine max L. Merr.) lines, Pl-416937 (Al-tolerant) and Essex (Al-sensitive). Following exposure to 80μM Al for up to 2 h, roots were rinsed with a 10 mM potassium citrate solution and rapidly dissected to allow estimation of intracellular Al accumulation in morphologically
distinct root regions. Using 10 min exposures to 300μM
15NO3
− and dissection, accompanying effects on NO3
− uptake were measured. With Al exposures of 20 min or 2 h, there was greater Al accumulation in all root regions of Essex
than in those of Pl-416937. The genotypic difference in Al accumulation was particularly apparent at the root apex, both in
the tip and in the adjacent root cap and mucilage. Exposure of roots to Al inhibited the uptake of 15NO3
− to a similar extent in all root regions. The results are consistent with Al exclusion from cells in the root apical region
being an important mechanism of Al tolerance. 相似文献
7.
InMucuna pruriens var.utilis, grown with nitrate-N in a hydroponic split-root system, an Al avoidance reaction of root growth was observed, which was ascribed to local P stress in the Al containing compartment. The Al avoidance reaction was similar to the avoidance ofMucuna roots of acid subsoil in the field where roots grew preferentially in the topsoil. In the present paper the effect of different N forms (NO3
– and NH4
+) on the reactions ofMucuna to Al were studied, since in acid soils N is present as a mixture of NO3
– and NH4
+. No interaction between the N form and Al toxicity was found. A hydroponic split-root experiment with NH4NO3 nutrition, which is comparable to the situation in the field, showed that under these conditions Al avoidance did not occur. It is concluded that a relation between the Al avoidance reaction ofMucuna and P stress is still likely.Abbreviations Dr
root diameter
- Lpr
total root length per plant
- Lrw
specific root length
- NRA
nitrate reductase activity
- S/R
shoot: root ratio 相似文献
8.
Effects of aluminium on growth and root reactions of phosphorus stressed Betula pendula seedlings 总被引:1,自引:0,他引:1
The impact of two constant non-toxic levels of Al stress (0.2 and 0.4 mM) on growth and 32P uptake capacity on sub-optimal (P-limited) Betula pendula seedlings grown in sand culture was examined.Seedling growth was under optimum controlled conditions in a growth chamber where nutrient additions were made at a predetermined relative addition rate (RA) of 10% day-1. Three treatment groups of seedlings 0, 0.2 and 0.4 mM Al were harvested at 15, 29 and 42 days. The excised roots were exposed to a 32P-labelled solution for 15 minutes to measure their capacity for P uptake. Growth was determined by weighing the roots, stems and leaves of the seedlings.Growth data showed that relative growth rate (RG) should equal the RA of P the most limiting nutrient, which was supplied at P/N 3% instead of an optimal 15%. Therefore, Ingestad's theory can also be used succesfully in sand culture and this may be particularly important for future studies of root and rhizosphere exudates. Low levels of Al (< 0.2 mM) in combination with low P supply significantly lowered the RG of the birch seedlings by further reducing P supply. However, previous studies of birch seedling growth and nutrient uptake using Ingestad's solution culture technique with optimumal P supply did not show any effect of Al on growth untill the Al was in excess of 3 mM. Aluminium was not directly toxic to the plants and therefore roots could respond to the 32P bioassay. 相似文献
9.
Modelling of the dynamics of Al and protons in the rhizosphere of maize cultivated in acid substrate 总被引:3,自引:0,他引:3
The object of this study was to analyze the dynamics of Al and protons in the rhizosphere of maize cultivated in a simple
acid substrate, so as to allow the use of a dynamic model of the functioning of a rhizosphere consisting of an organic phase
(an agarose gel) and a mineral phase (an amorphous aluminium hydroxide). Two cultivars of maize (Zea mays L.), one Al-sensitive
and the other Al-tolerant, were cultivated on this substrate in the presence of different proportions of NH
4
+
and NO
3
-
, which served to acidify the rhizosphere to a greater or lesser extent. The state of the agarose gel and of the cell walls
of the roots were monitored using an ion exchange model which had previously been calibrated for each substrate.
The experiment showed that Al and protons reduce root growth and the Ca and Mg content in the root, while relative growth
varies little between pH 4.0 and pH 4.5. The model showed that competition between Al and protons for the binding sites of
the cell walls might account for these results. The sensitivity of the model to the rate of Al(OH)3 dissolution and to the cation exchange capacity of the culture substrate was tested by numerical simulation. When roots release
protons and dissolve Al(OH)3 in the rhizosphere, there is little possibility of Al desorption by protons on the cell walls at pHs compatible with good
root growth of maize, plant specie sensitive to Al and H. Furthermore, the phytotoxicity of the different forms of Al hydroxides
should be considered only in taking into account the dynamics of the whole system, in particular the solubilisation of Al
in the rhizosphere.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
Gerd Johansson 《Plant and Soil》1993,151(1):11-20
Distribution of net assimilated C in meadow fescue (Fectuca pratensi L.) was followed before and after cutting of the shoots. Plants were continuously labelled in a growth chamber with 14C-labelled CO2 in the atmosphere from seedling to cutting and with 13C-labelled CO2 in the atmosphere during regrowth after the cutting. Labelled C, both 14C and 13C, was determined at the end of the two growth periods in shoots, crowns, roots, soil and rhizosphere respiration.
Distribution of net assimilated C followed almost the same pattern at the end of the two growth periods, i.e. at the end of
the 14C- and the 13C-labelling periods. Shoots retained 71–73% of net assimilated C while 9% was detected in the roots and 11–14% was released
from the roots, determined as labelled C in soil and as rhizosphere respiration.
At the end of the 2nd growth period, after cutting and regrowth, 21% of the residual plant 14C at cutting (14C in crowns and roots) was found in the new shoot biomass. A minor part of the residual plant 14C, 12%, was lost from the plants. The decreases in 14C in crowns and roots during the regrowth period suggest that 14C in both crowns and roots was translocated to new shoot tissue.
Approximately half of the total root C at the end of the regrowth period after cutting was 13C-labelled C and thus represents new root growth. Root death after cutting could not be determined in this experiment, since
the decline in root 14C during the regrowth period may also be assigned to root respiration, root exudation and translocation to the shoots. ei]{gnH}{fnLambers}
ei]{gnA C}{fnBorstlap} 相似文献
11.
Two kinds of Polygonum species (Polygonum aviculare L. and Polygonum lapathifolium L.) grown in tea garden soils at pH around 3.5 and one Polygonum bungeanum Turcz grown in neutral soils were collected to investigate the mechanisms involved in their high Al resistance. Hydroponic
experiments showed that the root elongation was only inhibited by 15% in P. aviculare and 35% in P. lapathifolium after exposure to 50 μM Al for 24 h. Their Al resistance was respectively higher than and similar to that in an Al resistant
buckwheat (Fagopyrum esculentum Moench) cultivar. In contrast, P. bungeanum was much more Al sensitive since the root elongation was inhibited by 80% under the same condition. The difference in Al
resistance among Polygonum species was confirmed in a 10-d intermittent Al treatment experiment, the root biomass of the first two species were unaltered
and decreased by 50% in the latter species. However, high Al accumulation was not found in the leaves, indicating these species
were not Al accumulators. Oxalate efflux was detected in root exudates of both Al resistant species, efflux initiated within
30 min treatment of 50 μM Al. No organic acid anions were detected in the root exudates of the Al sensitive species. The anion
channel inhibitor phenylglyoxal (PG) inhibited the oxalate efflux greatly. Inhibition of root elongation was greater in the
presence of PG, confirming that oxalate efflux was associated with the Al resistance. However, since the efflux rate was much
lower than their related species buckwheat, other mechanisms must be involved in Al resistance and these need to be studied
further. 相似文献
12.
Little information is known on what the magnitude of nitrogen (N) processed by ectomycorrhizal (ECM) fungal species in the
field. In a common garden experiment performed in a northern California oak woodland, we investigated transfer of nitrogen
applied as 15NH4 or 15NO3 from leaves to ectomycorrhizal roots of three oak species, Quercus agrifolia, Q. douglasii, and Q. garryana. Oak seedlings formed five common ectomycorrhizal morphotypes on root tips. Mycorrhizal tips were more enriched in 15N than fine roots. N transfer was greater to the less common morphotypes than to the more common types. 15N transfer from leaves to roots was greater when , not , was supplied. 15N transfer to roots was greater in seedlings of Q. agrifolia than in Q. douglasii and Q. garryana. Differential N transfer to ectomycorrhizal root tips suggests that ectomycorrhizal morphotypes can influence flows of N
from leaves to roots and that mycorrhizal diversity may influence the total N requirement of plants. 相似文献
13.
Anika K. Richter Lorenz Walthert Emmanuel Frossard Ivano Brunner 《Plant and Soil》2007,298(1-2):69-79
It is generally believed that high soil solution Al3+ in acidic soils with low base saturation (BS), negatively influences the properties of fine roots. Fine roots from European
beech (Fagus sylvatica L.) trees growing in highly acidic soils with very low BS and potentially high Al3+ concentration in the soil solution were analysed and the dependency of fine root properties on soil BS was measured. The
fine roots were sampled down to 1 m depth at seven forest sites located on the Swiss Plateau. These sites varied in their
BS from 1.4 to 11.4% in the mineral layers. We evaluated relationships between the BS of these mineral layers and fine root
properties, such as ratio between bio- and necromass (live/dead ratio), specific root length (SRL), root tip abundance (RTA),
root branching abundance (RBA), O2-consumption, and the Ca/Al molar ratio in the fine root tissue. The fine root properties were compared not only with the
BS of the soil, but also with the Ca/Al molar ratio in the fine root tissues. Significant relations of fine root properties
occurred when the soils of the seven sites were grouped into two BS groups (<5 and 5–10%). The live/dead ratio, the RTA, the
RBA, the O2-consumption, and Ca/Al molar ratio were lower in the group of BS <5% than in the group 5–10%. Decreases in the morphological
properties and in the O2-consumption were related to decrease in the Ca/Al molar ratio of the fine root tissues. There is evidence that the fine root
properties are negatively influenced, nevertheless, fine root systems of mature European beech in their natural ecological
environment seem to be able to compensate adverse effects of low BS.
Responsible Editor: Philippe Hinsinger. 相似文献
14.
Forest die-back and impaired tree vitality have frequently been ascribed to Al-toxicity and Al-induced nutritional disorders
due to increased acidification of forest soils. Therefore, in this experiment effects of Al were studied on growth and nutrient
uptake with seedlings of five different forest tree species. During growth in culture solutions with and without Al all five
species proved to be very Al-tolerant, despite high accumulation of Al in roots. In the coniferous evergreens Douglas-fir
and Scots pine shoot as well as root Al concentrations were significantly higher than in the deciduous broad-leaved species
oak and birch. Larch showed intermediate Al levels.
In none of the five species did Al reduce nutrient concentrations or the Ca/Al ratio to values below the critical level. Besides
differences in Al accumulation, coniferous and broad-leaved species also differed with respect to uptake and assimilation
of nitrogen. Due to extra NH
4
+
uptake, oak and birch showed a much higher N uptake and higher NH
4
+
preference than the coniferous species. Especially with oak this high NH
4
+
preference in combination with a low specific root surface area resulted in a high root proton efflux density. In comparison
to both broad-leaved trees and Scots pine the NO
3
−
reduction capacity of larch and Douglas-fir was extremely low. This may have important consequences for both species if grown
in NO
3
−
-rich soils. 相似文献
15.
Aluminum-induced cell death of barley-root border cells is correlated with peroxidase- and oxalate oxidase-mediated hydrogen peroxide production 总被引:10,自引:0,他引:10
Tamás L Budíková S Huttová J Mistrík I Simonovicová M Siroká B 《Plant cell reports》2005,24(3):189-194
The function of root border cells (RBC) during aluminum (Al) stress and the involvement of oxalate oxidase, peroxidase and H2O2 generation in Al toxicity were studied in barley roots. Our results suggest that RBC effectively protect the barley root tip from Al relative to the situation in roots cultivated in hydroponics where RBC are not sustained in the area surrounding the root tip. The removal of RBC from Al-treated roots increased root growth inhibition, Al and Evans blue uptake, inhibition of RBC production, the level of dead RBC, peroxidase and oxalate oxidase activity and the production of H2O2. Our results suggest that even though RBC actively produce active oxygen species during Al stress, their role in the protection of root tips against Al toxicity is to chelate Al in their dead cell body. 相似文献
16.
A soil incubation and short-term root growth experiment was conducted to investigate the effects of organic matter application
on Al toxicity alleviation in a highly weathered acid soil. Ground leaves of a tree legume (Calliandra calothyrsus Meissn.), ground barley (Hordeum vulgare L.) straw, or CaCO3 were mixed at various rates with A-horizon soil of a red podzolic soil (Epiaquic Haplustult) and incubated at 90% of field
capacity for 4 or 10 weeks. After the incubation, a short term (48 h) root growth test was conducted using mung bean (Vigna radiata (L.) Wilczek), followed by the analysis of the solution and solid phases of the post-harvest soil.
Adding either CaCO3 or organic matter increased root length in mung bean largely by decreasing the activity of monomeric Al in the soil solution.
With organic matter, the major mechanisms of this decrease were presumed to be precipitation of soluble Al and the formation
of Al-organic matter complexes. The former effect was predicted from the pH increase accompanying the organic matter addition,
the increase being larger with legume leaves which had the higher exchangeable and soluble Ca and Mg contents. The concentration
of Al complexed with soluble organic matter also was shown to increase with increasing rate of organic matter addition, the
effect again being larger with legume leaves.
The sum of monomeric Al species activity and Al3+ activity was negatively correlated with relative root length for the organic matter and CaCO3 treatments. However, indices which took into account the possible alleviation effects of basic cations in soil solution on
Al toxicity provided an improvement in correlation with relative root length.
The efficiency of the two organic amendments relative to CaCO3 in decreasing Al toxicity was assessed by comparing the rates required to reduce Al3+ activity below 10 μ M, the value found to be associated with 90% relative root length for mung bean. The rates of CaCO3, legume leaf and barley straw required to reach this critical value were 0.75, 14, and 42 t ha−1 respectively. 相似文献
17.
Muhammad Riaz Xiuwen Wu Lei Yan Saddam Hussain Omar Aziz Asad Shah 《Journal of Plant Interactions》2018,13(1):270-276
Aluminum (Al) toxicity is one of the major problems affecting crop production. Boron (B) is an essential micronutrient for higher plants. In the present study, we investigated the alleviation of Al-induced inhibition of root growth and physiological characteristics by B in rapeseed. The rapeseeds were grown in different Al concentrations (0 and 300?μM), and for every concentration, two B treatments (2.5 and 25?µM as H3BO3) were applied. The results showed that Al toxicity under low B drastically inhibited root growth. The supply of B improved root length, photosynthesis, root activity, total chlorophyll by 60.15%, 104.7%, 102%, and 106.3%, respectively under Al toxicity. This further resulted in improvement of peroxidase, catalase, and ascorbate peroxidase activities while decreasing malondialdehyde, H2O2, and Al contents in roots and leaves. It might be supposed that B alleviates Al toxicity by less mobilization of Al in plant parts and through improving antioxidant enzyme activities. 相似文献
18.
The extremely high Al resistance of Penicillium janthineleum F-13 is not caused by internal or external sequestration of Al 总被引:1,自引:0,他引:1
Penicillium janthinellum F-13 has been isolated in previous work as a fungus tolerating the presence of high concentrations of Al (as high as 100 mM AlCl3). Here its growth rate and yield in three acidic (pH 3.0) media of different composition with varying concentrations of Al are reported. The presence of Al did not affect these parameters, except that the growth yield was somewhat lower in GM (a glucose/peptone/yeast extract-containing medium) with the highest concentration tested (100 mM AlCl3). The amount of Al found in the mycelium was so low that it cannot lead to a significant decrease in the medium for the higher Al concentrations applied. Although citric acid was excreted at growth on GM, and the presence of Al even promoted this, the concentration of this was far too low to diminish (by chelation) the high Al concentrations in the medium to a non-toxic level, i.e. the level (of approx. 1 mM) that is tolerated by low-resistance fungi. At growth on SLBM (a peptone/yeast extract/soil extract-containing medium), a rise in pH occurred. The same was found for SM (a glucose/mineral salts-containing medium), although in this case the picture was more complicated because the initial rise in pH was followed by a lowering due to the excretion of oxalic acid. Although both phenomena can diminish Al toxicity (by decreasing the external concentration of monomeric Al, regarded to be the toxic species), again the decrease is far too low to attain a non-toxic level when high Al concentrations are applied. Therefore, although in principal the metabolic phenomena observed for P. janthinellum F-13 at growth on different media can diminish Al toxicity, the tolerance of this organism for high external Al concentrations must be caused by another mechanism. 相似文献
19.
K. Ohki 《Plant and Soil》1987,98(2):195-202
Summary Sorghum plants were grown in the greenhouse in modified Steinberg nutrient solution containing ten Al rates (0 to 297 μM) and harvested 28 days after transplanting. Top and root dry weight were not affected by added Al up to 74 μM; but decreased sharply at concentration of 148 μM and greater. Aluminum concentrations in blade 1 (recently matured blade) and plants remained constant from 0 to 297 μM added Al. Root Al concentration increased as added Al increased. No correlation existed between top dry weight and Al concentration
in blade 1 or in plant. Root Al concentration was related to top dry weight and root dry weight to estimate the Al critical
toxicity level. The Al critical toxicity levle in the root was 54 mmol kg−1 root dry weight basis for either top or root dry weight. In blade 1 Cu concentration negatively correlated with Al while
Fe and P were positively correlated. In roots Ca, Mg, Mn and Fe concentrations were negatively correlated with Al while Zn,
Cu, P, and K were positively correlated with Al concentration. 相似文献
20.
The influence of phosphate deficiency on the sugar accumulation and sugar partitioning in the root cells of bean (Phaseolus
vulgaris L.) was studied. Bean plants were cultured 17 - 19 d on a phosphate-sufficient and phosphate-deficient nutrient medium.
Phosphate deficit in the growth medium resulted in increased sugar concentration for about 30 % in the apoplastic and cytoplasmic
compartments as well as in the vacuoles of root cells. However, the distribution of sugars between apoplast and cytoplasm
compartment and vacuole was not affected by decreased phosphate concentration. About 20 % of sugars were found in the apoplast
and cytoplasm, about 80 % in the vacuole. Low phosphate concentration enhanced influx of exogenous 14C-sucrose into meristematic and elongation zones of root. The 14C-labelled sugar content in the root tips increased for about 60 % as compared to control plants. Phosphate deficiency increased
also 14C-glucose uptake and content in the root tips. However, the amount of 14CO2 liberated during respiration of P-deficient roots (after feeding with uniformly labelled 14C-glucose) was lower than 14CO2 respired by control plants, thus a large part of accumulated sugars seems to be metabolically inactive.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献