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1.
Xiu-Yun Cheng Wen-Yin Chen Bin-He Gu Xu-Cheng Liu Fang Chen Zhang-He Chen Xian-Ye Zhou Yu-Xiang Li Hua Huang Yun-Jin Chen 《Hydrobiologia》2009,623(1):77-85
The objective of this study was to test the hypothesis that fibrous-root plants and rhizomatic-root plants are characterized
by different root morphologies, root growth and distribution, and contaminant removal capabilities. Four fibrous-root and
four rhizomatic-root wetland plants were studied in mono-cultured microcosms which received wastewater. Fibrous-root plants
had significantly greater (P < 0.05) small-size root (diameter ≤ 1 mm) biomass and a larger (P < 0.05) root surface area per plant than the rhizomatic-root plants and exhibited accelerated growth in both shoots and roots
compared to the rhizomatic-root plants. Fibrous-root plants developed the majority of their root biomass increment within
a shallower gravel medium than the rhizomatic-root plants. All plants demonstrated fast root biomass growth from July to September.
The wetland microcosms planted with fibrous-root plants showed significantly higher (P < 0.05) ammonium-nitrogen (NH4-N) and nitrate-nitrogen (NO3-N) removal rates from July to December than those planted with the rhizomatic-root plants. These results suggest that root
characteristics of wetland plants, which are related to their shoot and root growth, root distribution, and decontamination
ability, can be used in the selection of wetland plants with a higher contaminant removal capacity and in the construction
of a multi-species wetland plant community.
Handling editor: S. M. Thomaz 相似文献
2.
A pot experiment was conducted to study the effects of root pruning at the stem elongation stage on the growth and water use
efficiency (WUE) of winter wheat (Triticum aestivum). The results showed that stomatal conductance (g) and transpiration (E) of wheat were very sensitive to root pruning. After root pruning, they declined rapidly and but returned to pre-pruning
values 15 days after treatment. Under well-watered conditions, there was no significant difference in leaf water potential
(ψleaf) between root pruned and control plants after root pruning. Under moderate drought stress, ψleaf of root pruned plants declined significantly compared to the control 3 days after root pruning. After 15 days, ψleaf of root pruned plants was similar to the controls. Under different soil moisture levels, net assimilation rate (A) of root pruned plants was lower than controls 3–7 days after root pruning, but was similar to the controls 15 days after
pruning. At anthesis (50 days after root pruning), root pruned plants showed significantly higher A compared with the control. Leaf area per tiller and tiller number of root pruning plants was significant lower than the control
at booting stage, which showed that root pruning restrained the growth of plants in the early growing stage, but leaf area
per stem, of root pruned plants, was similar to the control at anthesis. Under both soil moisture levels, there was no significant
difference in grain yield between root pruned and the control plants in the monoculture. In mixture with the control plants,
the root pruned plants was less productive and had a lower relative yield (0.92 and 0.78, respectively) compared with the
control (1.13 and 1.19, respectively), which suggested that the pruned plants lost some of its competing ability and showed
a lower ability to acquire and use the same resources in the mixture compared with the control plant. Over the whole growing
cycle, root pruning reduced water consumption (by 10% under well-watered conditions and 16% under moderate drought stress)
of wheat significantly compared to the control (P < 0.05), and but there was no significant difference in grain yield between root pruned and control plants. Therefore root
pruned wheat had a higher WUE with respect to grain yield compared with the controls. In conclusion, lowering water consumption
by root pruning in the early growing stage is an effective way to improve water use efficiency in arid and semi arid areas. 相似文献
3.
A comparison was made of energy metabolism of nodulated N2 fixing plants and non-nodulated NO3-fed plants of Lupinus albus L. Growth, N-increment, root respiration (O2 uptake and CO2 production) and the contribution of a SHAM-sensitive oxidative pathway (the alternative pathway) in root respiration were measured. Both growth rate and the rate of N-increment were the same in both series of plants. The rate of root respiration, both O2 uptake and CO2 production, and the activity of the SHAM-sensitive pathway were higher in NO3-fed plants than in N2 fixing plants. The rate of ATP production in oxidative phosphorylation was computed also to be higher in NO3-fed plants. It is concluded that both carbohydrate costings and ATP costings for synthesis + maintenance of root material were lower in N2 fixing than in NO3-fed plants. The respiratory quotient of root respiration was 1.6 in N2-fixing plants and 1.4 in NO3-fed plants. These values were slightly higher than the values calculated on the basis of CO2 output due to N-assimilation and the experimental values of O2 uptake, but showed the same trend: highest in N2 fixing plants. Root respiration of NO3-fed plants showed a diurnal pattern (both O2 uptake, CO2 production and the activity of the SHAM-sensitive pathway), whilst no diurnal variation in root respiration was found in N2 fixing plants. However, C2H2 reduction did show a diurnal rhythm, which is suggested to be related to the diurnal variation in transpiration. Addition of NO3 to N2 fixing plants increased the rate of root respiration and the activity of the alternative pathway. This treatment did not decrease C2H2 reduction and H2 evolution within 4 days. Withdrawal of NO3-supply from NO3-fed plants decreased the rate of root respiration but had no effect on the relative activity of the alternative pathway. It is suggested that the higher rate of root respiration and the higher activity of the SHAM-sensitive pathway in NO3-fed plants is due to a larger supply of carbohydrates to the roots, partly due to a better photosynthetic performance of the shoots and partly due to a higher capacity of the roots to attract carbohydrates. 相似文献
4.
5.
Effects of increasing inorganic carbon supply to roots on net nitrate uptake and assimilation in tomato seedlings 总被引:2,自引:0,他引:2
We investigated the influence of an increased inorganic carbon supply in the root medium on NO?3 uptake and assimilation in seedlings of Lycopersicon esculentum (L.) Mill. cv. F144. The seedlings were pre-grown for 4 to 7 days with 0 or 100 mM NaCl in hydroponic culture using 0.2 mM NO?3 (group A) or 0.2 mM NH+4 (group B) as nitrogen source. The nutrient solution for group A plants was aerated with air or with air containing 4 800 μumol mol?1 CO2. Nitrate uptake rate and root and leaf malate contents in these plants were determined. The plants of group B were subdivided into two sets. Plants of one set were transferred either to N-free solution containing 0 or 5 mM NaHCO3, or to a medium containing 2 mM NO?3 and 5 mM NaHCO3. Both sets of group B plants were grown for 12 h in darkness prior to 2 h of illumination, and were assayed for malate content and NO?3 uptake rate (only for plants grown in N-free solution). The second set of group B plants was labeled with 14C by a 1-h pulse of H14CO?3 which was added to a 5 mM NaHCO3 solution containing 0 or 100 mM NaCl and 0 or 2 mM NO?3, and 14C-assimilates were extracted and fractionated. The roots of group B plants growing in carbonated medium accumulated twice as much malate as did control plants. This malate was accumulated only when NO?3 was absent from the root medium. Both a high level of root malate and aeration with CO2-enriched air stimulated NO?3 uptake. Analysis of 14C-assimilates indicated that with no NO?3 in the medium, the 14C was present mainly in organic acids, whereas with NO?3, a large proportion of 14C was incorporated into amino acids. Transport of root-incorporated 14C to the shoot was enhanced by NO?3, while the amino acid fraction was the major 14C-assimilates in the shoot. It is concluded that inorganic carbon fixed through phosphoenolpyruvate carboxylase (EC 4.1.1.31) in roots of tomato plants may have two fates: (a) as a carbon skeleton for amino acid synthesis; and (b) to accumulate, mainly as malate, in the roots, in the absence of a demand for the carbon skeleton. Inorganic carbon fixation in the root provides carbon skeletons for the assimilation of the NH+4 resulting from NO3 reduction, and the subsequent removal of amino acids through the xylem. This ‘removal’ of NO?3 from the cytoplasm of the root cells may in turn increase NO?3 uptake. 相似文献
6.
Although nutrient stress is known to alter partitioning between shoots and roots, the physiological basis for the phenomenon is unresolved. Experiments were conducted to examine assimilation of 15NO3 by N-stressed plants and to determine whether apparent changes in assimilation in the root contributed to alterations in whole-plant partitioning of reduced-N. Tobacco plants (Nicotiana tabacum L. cv. NC 2326) were exposed to a low concentration of NO3? in solution (80 μM) for 9 days to effect a N-stress response. Exposure of plants to 1000 μM15NO3? for 12 h on selected days revealed that roots of N-stressed plants developed an increased capacity to absorb NO3?, and accumulation of reduced-15N in the root increased to an even greater extent. When plants were exposed to 80 or 1000 μM15NO3? in steady-state, 15NO3? uptake over a 12 h period was noticeably restricted at the lower concentration, but a larger proportion of the absorbed 15N still accumulated as reduced-15N in the root. The alteration in reduced-15N partitioning was maintained in N-stressed plants during the subsequent 3-day “chase” period when formation of insoluble reduced-15N in the root was quantitatively related to the disappearance of 15NO3? and soluble reduced-15N. The results indicate that increased assimilation of absorbed NO3?, in the root may contribute significantly to the altered reduced-N partitioning which occurs in N-stressed plants. 相似文献
7.
The effects of an E-strain fungus (Wilcoxina mikolae var. mikolae) and an ectomycorrhizal fungus (Hebeloma crustuliniforme) on growth and water relations of balsam poplar were examined and compared in the present study. Balsam poplar roots inoculated
with W. mikolae var. mikolae (Wm) exhibited structures consistent with ectendomycorrhizal (EEM) associations, including a mantle surrounding the outside
of the root and an extensive Hartig net that was located between cortical cells and extended to the vascular cylinder. Roots
colonized with H. crustuliniforme (Hc) developed a mantle layer, indicative of an ectomycorrhizal (ECM) association, around the outer part of the root, but
no distinct Hartig net was present. Wm-colonized balsam poplar also showed increased shoot growth, stomatal conductance (g
s), and root volumes compared with non-inoculated and Hc-inoculated plants. However, Hc-inoculated plants had higher root hydraulic
conductivity (L
pr) compared with non-inoculated plants and Wm-inoculated plants. These results suggest that L
pr was not a growth-limiting factor in balsam poplar and that hyphal penetration of the root cortex in itself may have little
influence on root hydraulic properties. 相似文献
8.
The effects of atmospheric CO2 enrichment and root restriction on photosynthetic characteristics and growth of banana (Musa sp. AAA cv. Gros Michel) plants were investigated. Plants were grown aeroponically in root chambers in controlled environment glasshouse rooms at CO2 concentrations of 350 or 1 000 μmol CO2 mol-1. At each CO2 concentration, plants were grown in large (2001) root chambers that did not restrict root growth or in small (20 1) root chambers that restricted root growth. Plants grown at 350 μmol CO2 mol-1 generally had a higher carboxylation efficiency than plants grown at 1 000 μmol CO2 mol-1 although actual net CO2 assimilation (A) was higher at the higher ambient CO2 concentration due to increased intercellular CO2 concentrations (Ci resulting from CO2 enrichment. Thus, plants grown at 1 000 μmol CO2 mol-1 accumulated more leaf area and dry weight than plants grown at 350 μmol CO2 mol-1. Plants grown in the large root chambers were more photosynthetically efficient than plants grown in the small root chambers. At 350 μmol CO2 mol-1, leaf area and dry weights of plant organs were generally greater for plants in the large root chambers compared to those in the small root chambers. Atmospheric CO2 enrichment may have compensated for the effects of root restriction on plant growth since at 1 000 μmol CO2 mol-1 there was generally no effect of root chamber size on plant dry weight. 相似文献
9.
Rare earth elements (REEs) in five species of soil-grown plants (Taxodium japonicum, Populus sieboldii, Sasa nipponica, Thea sinensis and Vicia villosa) and in the soil on which each plant grew were determined with an inductively coupled plasma mass spectrometer (ICP-MS) in order to observe the variation in the distribution of REEs and to elucidate their source in soil-grown plants. The plant samples were divided into root (secondary root and main root), trunk (stem) and leaf; the soils into water soluble (soilsoluble
fraction), HCl and HNO3 soluble (soilnon-silicate
fraction) and HF soluble (soilsilicate
fraction). The REE abundances of samples were compared using REE patterns where the abundances were normalized to those of a chondrite and plotted on a logarithmic scale against the atomic number. All the plants showed similar REE patterns independent of species and location, and a W-shape variation (W-type tetrad effect) and abundance depletion of cerium (negative Ce anomaly) were found in each REE patterns of plants, more conspicuous tetrad effect being observed in HREE (heavier rare earth elements) region than in LREE (lighter rare earth elements) region. The overall variation of REE patterns of each secondary root was not similar to that of soilsoluble
fraction, but similar to that of soilsilicate
fraction except for the tetrad effect and Ce anomaly. The REE patterns can be interpreted by the idea that plants of different species take in REEs and Si from different parts in the soil. The results of this study seem to imply that Sasa nipponica and Vicia villosa take in free REEs and Si rather directly from silicate in the soil, and that a majority of REEs and Si in Taxodium japonicum and Thea sinensis are originated from the soluble fraction in the soil. 相似文献
10.
A liquid meristematic root primordia culture (RPC) of Solanum lycopersicoides Dun. based on persistent rhizogenesis in a modified Murashige and Skoog (1962) medium supplemented with NAA (15 mg·l−1) or 2,4-D (1 mg·l−1) was described. The meristematic clumps (2–3 mm in diameter) originating from NAA supplemented medium were capable of regenerating
plants through the callus stage (up to 70 %). Efficient direct plant regeneration (up to 21 %) was possible from numerous
single globular-shaped root primordia (RP) structures liberated from the parental aggregates in 2,4-D supplemented proliferation
medium without NH4NO3 and with a 2.5 fold increase in KNO3. The RP converted into plantlets (artificial seedlings) on solid or liquid media without growth growth regulators through
the unipolar followed by the mace-shaped bipolar structure stages. The use of apical shoot bud, root apices or root segments
as a primary explants brought about RPC induction and plant regeneration. The plants derived from 2 years old culture were
phenotypically identical to their parental S. lycopersicoides plants and possessed the same ploidy. 相似文献
11.
The influx of K+(86Rb+) into intact roots of rye (Secale cereale L. cv. Rheidal) exposed to a differential temperature (DT) between the root (8° C) and shoot (20° C) is initially reduced compared with warm-grown (WG) controls with both shoot and root maintained at 20° C. Over a period of 3 d, however, K+-influx rates into DT plants are restored to levels similar to or greater than those of the WG controls, the absolute rates of K+ influx being strongly dependent upon the shoot/root ratio. Acclimation in DT plants results in a reduction of K+ influx into the apical (0–2 cm) region of the seminal root which is associated with a compensatory increase in K+ influx into the more mature, basal regions of the root. Values of V
max and apparent K
m for K+ influx into DT plants were similar to those for WG plants at assay temperatures of 8° C and 20° C except for an increase in the apparent K
m at 8° C. The influx of K+ from solutions containing 0.6 mol·m-3 K+ into both WG and DT plants was found to be linearly related to assay temperature over the range 2–27° C, and the temperature sensitivity of K+ influx to be dependent upon shoot/root ratio. At high shoot/root ratios, the ratio of K+ influx at 20° C:K+ influx at 8° C for WG plants approached a minimum value of 1.9 whereas that for DT plants approached unity indicating that K+ influx into DT plants has a large temperature-insensitive component. Additionally, when plants were grown in solutions of low potassium concentration, K+ influx into DT plants was consistently greater than that into WG plants, in spite of having a greater root potassium concentration ([K+]int). This result indicates some change in the regulation of K+ influx by [K+]int in plants exposed to low root temperatures. We suggest that K+ influx into rye seedlings exposed to low root temperatures is regulated by the increased demand placed on the root system by a proportionally larger shoot and that the acclimation of K+ influx to low temperatures may be the result of an increased hydraulic conductivity of the root system.Abbreviations DT
differential temperature pretreatment
- [K+]int
root potassium concentration
- [K+]ext
potassium concentration of nutrient medium
- WG
warm-grown pretreatment 相似文献
12.
The fate of nitrate and nitrogen-15 was followed during the apparent induction phase (6h) for nitrate uptake by N-depleted dwarf bean (Phaseolus vulgaris L. ev. Witte Krombek). Experiments were done with intact plants and with detached root systems. Qualitatively and quantitatively, xylem exudation from detached roots was a bad estimate of the export of NO?3 or NO?3-15N from roots of intact plants. In vivo nitrate reductase activity (NRA) agreed well with in situ reduction, calculated as the difference between uptake and accumulation in whole plants, provided NRA was assayed with merely endogenous nitrate as substrate (‘actual’ NRA). The majority (75%) of the entering nitrate remained unmetabolized. Both nitrate reduction and nitrate accumulation occurred predominantly in the root system. Some (< 25%) of the root-reduced nitrate-N was translocated to the shoot. Nitrate uptake occurred against the concentration gradient between medium and root cells, and probably against the gradient of the electro-chemical potential of nitrate. Part of the energy expended for NO?3 absorption came from the tops, since decapitation and ringing at the stem base restricted nitrate uptake. 相似文献
13.
Alfalfa (Medicago sativa L.) is a deeply rooted perennial legume which, under field conditions, may be exposed to varying NO3? concentrations with depth. Our objective was to characterize the effect of localized (deep vs shallow) exposure of alfalfa root systems to NO3? on symbiotic N2 fixation and NO3?-N uptake. Cuttings of a single alfalfa plant were grown in vertical split root systems in a controlled environment chamber. The split root system was a rigid acrylic tube (5 cm diam. by 60 cm long) filled with silica sand and divided into upper and lower sections at the 30-cm depth by a 5-mm-thick wax layer. Roots penetrated the wax layer, but mixing of nutrient solutions between the sections was prevented. Nodulation was restricted to the upper section. The plants were subjected for 10 days to the following treatments: both sections of the split root system received nutrient solution containing either 0.5, 5.25, or 10 mM NO3?; the upper section received 0.5 mM NO3? while the lower section received 10 mM NO3?; or the upper section received 10 mM NO3? while the lower section received 0.5 mM NO3?. Increasing supply of NO3? in the nutrient solution to both sections resulted in higher NO3?-N uptake, lower nodule mass and lower specific nitrogenase activity. Although NO3?-N uptake did not differ, plants exposed to 10 mM NO3? for 10 days in the upper, nodulated section of the root system had a 20% lower nodule mass than plants exposed to the same NO3? concentration in the lower, non-nodulated section of the root system. Specific nitrogenase activity was not different between these two treatments. Therefore, we conclude that: (1) nodule mass was dependent on two factors, the amount of NO3?-N taken up and the concentration of NO3? within the nodulated root zone; and (2) specific nitrogenase activity was little affected by the concentration of NO3? surrounding the nodules, but was strongly inhibited by NO3?-N taken up. 相似文献
14.
Our previous work indicated that salinity caused a shift in the predominant site of nitrate reduction and assimilation from the shoot to the root in tomato plants. In the present work we tested whether an enhanced supply of dissolved inorganic carbon (DIC, CO2+ HCO3) to the root solution could increase anaplerotic provision of carbon compounds for the increased nitrogen assimilation in the root of salinity-stressed Lycopersicon esculentum (L.) Mill. cv. F144. The seedlings were grown in hydroponic culture with 0 or 100mM NaCl and aeration of the root solution with either ambient or CO2-enriched air (5000 μmol mol?1). The salinity-treated plants accumulated more dry weight and higher total N when the roots were supplied with CO2-enriched aeration than when aerated with ambient air. Plants grown with salinity and enriched DIC also had higher rates of NO?3 uptake and translocated more NO?3 and reduced N in the xylem sap than did equivalent plants grown with ambient DIC. Incorporation of DIC was measured by supplying a 1 -h pulse of H14CO?3 to the roots followed by extraction with 80% ethanol. Enriched DIC increased root incorporation of DIC 10-fold in both salinized and non-salinized plants. In salinity-stressed plants, the products of dissolved inorganic 14C were preferentially diverted into amino acid synthesis to a greater extent than in non-salinized plants in which label was accumulated in organic acids. It was concluded that enriched DIC can increase the supply of N and anaplerotic carbon for amino acid synthesis in roots of salinized plants. Thus enriched DIC could relieve the limitation of carbon supply for ammonium assimilation and thus ameliorate the influence of salinity on NO?3 uptake and assimilation as well as on plant growth. 相似文献
15.
Humic acid differentially improves nitrate kinetics under low‐ and high‐affinity systems and alters the expression of plasma membrane H+‐ATPases and nitrate transporters in rice
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O.C.H. Tavares L.A. Santos L.M. Ferreira M.V.L. Sperandio J.G. da Rocha A.C. García L.B. Dobbss R.L.L. Berbara S.R. de Souza M.S. Fernandes 《The Annals of applied biology》2017,170(1):89-103
Humic acids (HAs) have a major effect on nutrient uptake, metabolism, growth and development in plants. Here, we evaluated the effect of HA pretreatment applied with a nutrient solution on the uptake kinetics of nitrate nitrogen (N‐NO3?) and the metabolism of nitrogen (N) in rice under conditions of high and low NO3? supply. In addition, the kinetic parameters of NO3? uptake, N metabolites, and nitrate transporters (NRTs) and the plasma membrane (PM) H+‐ATPase gene expression were examined. The plants were grown in a growth chamber with modified Hoagland and Arnon solution until 21 days after germination (DAG), and they were then transferred to a solution without N for 48 h and then to another solution without N and with and without the addition of HAs for another 48 h. After this period of N deprivation, the plants received new nutrient solutions containing 0.2 and 2.0 mM N‐NO3?. Treatment of rice plants with HA promoted the induction of the genes OsNRT2.1‐2.2/OsNAR2.1 and some isoforms PM H+‐ATPase in roots. The application of HAs differentially modified the parameters of the uptake kinetics of NO3? under both concentrations. When grown with 0.2 mM NO3?, the plants pretreated with HA had lower Km and Cmin values as well as a higher Vmax/Km ratio. When grown with 2 mM NO3?, the plants pretreated with HA had a higher Vmax value, a greater root and shoot mass, and a lower root/shoot ratio. The N fractions were also altered by pretreatment with HA, and a greater accumulation of NO3? and N‐amino was observed in the roots and shoots, respectively, of plants pretreated with HA. The results suggest that pretreatment with HA modifies root morphology and gene expression of PM H+‐ATPases and NO3? transporters, resulting in a greater efficiency of NO3? acquisition by high‐ and low‐affinity systems. 相似文献
16.
Summary Studies examined net photosynthesis (Pn) and dry matter production of mycorrhizal and nonmycorrhizalPinus taeda at 6 intervals over a 10-month period. Pn rates of mycorrhizal plants were consistently greater than nonmycorrhizal plants, and at 10 months were 2.1-fold greater. Partitioning of current photosynthate was examined by pulse-labelling with14CO2 at each of the six time intervals. Mycorrhizal plants assimilated more14CO2, allocated a greater percentage of assimilated14C to the root systems, and lost a greater percentage of14C by root respiration than did nonmycorrhizal plants. At 10 months, the quantity of14CO2 respired by roots per unit root weight was 3.6-fold greater by mycorrhizal than nonmycorrhizal plants. Although the stimulation of photosynthesis and translocation of current photosynthate to the root system by mycorrhiza formation was consistent with the source-sink concept of sink demand, foliar N and P concentrations were also greater in mycorrhizal plants.Further studies examined Pn and dry matter production ofPinus contorta in response to various combinations of N fertilization (3, 62, 248 ppm), irradiance and mycorrhizal fungi inoculation. At 16 weeks of age, 6 weeks following inoculation with eitherPisolithus tinctorius orSuillus granulatus, Pn rates and biomass were significantly greater in mycorrhizal than nonmycorrhizal plants. Mycorrhizal plants had significantly greater foliar %P, but not %N, than did nonmycorrhizal plants. Fertilization with 62 ppm N resulted in greater mycorrhiza formation than either 3 or 248 ppm. Increased irradiance resulted in increased mycorrhiza formation. 相似文献
17.
Comparison of Cadmium Effect on Willow and Poplar in Response to Different Cultivation Conditions 总被引:1,自引:0,他引:1
Salix alba L. and Populus×euroamericana cv. Robusta cuttings were grown in 10 μM Cd(NO3)2 (direct treatment) or in Knop solution and afterwards in Cd(NO3)2 (indirect treatment). Cd impact on rooting of directly treated plants and its impact on normally formed roots and shoots
of indirectly treated plants were studied. The cumulative length, number and biomass of willow roots, pigment and starch contents,
leaf net photosynthetic rate and dry mass/leaf area ratio of willow leaves were positively influenced by indirect treatment.
However, indirectly treated poplars were more sensitive to Cd than directly treated ones. Indirect treatment lowered root
Cd uptake in willow, Cd accumulation in cuttings of both species and Cd accumulation in poplar shoots. Cd-caused structural
changes were similar in both species and in both treatments. Root apices, rhizodermis and cortex were the most seriously damaged
root parts. In directly treated willow, the structure of central cylinder (0.5 – 1 cm from apex) remained unchanged in contrast
to indirectly treated plants. Formation of cambium close to the apex indicated shortening of root elongation zone of indirectly
treated plants. Directly Cd-treated poplar roots exhibited unusual defence activity of root apical meristem and accumulation
of darkly stained material around central cylinder.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
The effect of root growth temperature on maximal photosynthetic CO2 assimilation (P
max), carbohydrate content, 14C-photoassimilate partitioning, growth, and root morphology of lettuce was studied after transfer of the root system from
cool root-zone temperature (C-RZT) of 20 °C to hot ambient-RZT (A-RZT) and vice versa. Four days after RZT transfer, P
max and leaf total soluble sugar content were highest and lowest, respectively, in C-RZT and A-RZT plants. P
max and total leaf soluble sugar content were much lower in plants transferred from C-to A-RZT (C→A-RZT) than in C-RZT plants.
However, these two parameters were much higher in plants transferred from A-to C-RZT (A→C-RZT) than in A-RZT plants. A-RZT
and C→A-RZT plants had higher root total soluble sugar content than A→C-RZT and C-RZT plants. Leaf total insoluble sugar content
was similar in leaves of all plants while it was the highest in the roots of C-RZT plants. Developing leaves of C-RZT plants
had higher 14C-photoassimilate content than A-RZT plants. The A→C-RZT plants also had higher 14C-photoassimilate content in their developing leaves than A-RZT plants. However, more 14C-photoassimilates were translocated to the roots of A-RZT and C→A-RZT plants, but they were mainly used for root thickening
than for its elongation. Increases in leaf area, shoot and root fresh mass were slower in C→A-RZT than in C-RZT plants. Conversely,
A→C-RZT plants had higher increases in these parameters than A-RZT plants. Lower root/shoot ratio (R/S) in C-RZT than in A-RZT
plants confirmed that more photoassimilates were channelled to the shoots than to the roots of C-RZT plants. Roots of C-RZT
plants had greater total length with a greater number of tips and surface area, and smaller average diameter as compared to
A-RZT plants. In C→A-RZT plants, there was root thickening but the increases in its length, tip number and surface area decreased.
The reverse was observed for A→C-RZT plants. These results further supported the idea that newly fixed photoassimilates contributed
more to root thickening than to root elongation in A-RZT and C→A-RZT plants. 相似文献
19.
叶片和根系是植物获取资源的最重要的器官,其性状随环境梯度的变化反映了植物光合碳获取和水分与养分的吸收能力及其对环境变化适应的生态对策。羌塘高原降水梯度带高寒草地群落叶片和根系成对性状关系研究不仅能揭示环境梯度对植物性状的塑造作用,也可为理解寒、旱和贫瘠等极端环境下植物的适应策略提供依据。为此,选择3组具有代表性的叶片和根系成对性状:比叶面积(SLA)和比根长(SRL);单位质量叶氮含量(LNmass)和单位质量根氮含量(RNmass);单位面积叶氮含量(LNarea)和单位长度根氮含量(RNlength),分析不同优势植物地上、地下成对性状变异特征及其与环境因子的关系,探讨植物性状对高寒生态系统水分和养分限制因素的适应策略。研究表明,区域气候和土壤环境导致的叶片性状变异大于根系性状的变异,干旱端的植物既具有高的SRL,又具有高的叶片和根系的养分含量(LNmass,LNarea和RNmass)。SLA-SRL、LNmass 相似文献
20.
Ammonia-oxidizing bacteria on root biofilms and their possible contribution to N use efficiency of different rice cultivars 总被引:12,自引:0,他引:12
Briones Aurelio M. Okabe Satoshi Umemiya Yoshiaki Ramsing Niels-Birger Reichardt Wolfgang Okuyama Hidetoshi 《Plant and Soil》2003,250(2):335-348
Ammonia-oxidizing bacteria (AOB) populations were studied on the root surface of different rice cultivars by PCR coupled with denaturing gradient gel electrophoresis (DGGE) and fluorescence in situ hybridization (FISH). PCR-DGGE of the ammonium monooxygenase gene (amoA) showed a generally greater diversity on root samples compared to rhizosphere and unplanted soil. Sequences affiliated with Nitrosomonas spp. tended to be associated with modern rice hybrid lines. Root-associated AOB observed by FISH were found within a discrete biofilm coating the root surface. Although the total abundance of AOB on root biofilms of different rice cultivars did not differ significantly, there were marked contrasts in their population structure, indicating selection of Nitrosomonas spp. on roots of a hybrid cultivar. Observations by FISH on the total bacterial community also suggested that different rice cultivars support different bacterial populations even under identical environmental conditions. The presence of active AOB in the root environment predicts that a significant proportion of the N taken up by certain rice cultivars is in the form of NO3
–-N produced by the AOB. Measurement of plant growth of hydroponically grown plants showed a stronger response of hybrid cultivars to the co-provision of NH4
+ and NO3
–. In soil-grown plants, N use efficiency in the hybrid was improved during ammonium fertilization compared to nitrate fertilization. Since ammonium-fertilized plants actually receive a mixture of NH4
+ and NO3
– with ratios depending on root-associated nitrification activity, these results support the advantage of co-provision of ammonium and nitrate for the hybrid cultivar. 相似文献