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11.
The effect of calcium on the nodulation of lucerne was studied using EGTA, a specific calcium-chelator. First, the effects
of the chelator were tested on hydroponically grown plants at pH 7.0. Optimal numbers of nodules were obtained in nutrient
solution containing 0.2 mM CaCl2. When 0.4 mM EGTA was given additionally, nodulation was completely inhibited. Nodulation was restored specifically with CaCl2, but not with MgCl2.
For studies in an acid soil (pH-H2O 5.2), lucerne seedlings were grown in rhizotrons. 67% of the seedlings became nodulated when the soil around the seed was
neutralized locally with 1.0 μmol of K2CO3 in drops of 12 μL volume. When native calcium was removed with 2 μmol of EGTA, nodulation was reduced to 12%. However, addition of EGTA to soil resulted in a drop of pH from 6.1 to 5.2. A
phosphate buffer could also not keep soil-pH sufficiently stable. Such pH-decreases could be avoided by placing agar blocks
containing 6 μmol of EGTA for three hours on freshly developed roots. This treatment reduced nodulation from 87% to 32%, with soil-pH lowering
only from 6.2 to 6.0. Nodulation could be restored by adding 2 μmol of CaCl2. The depletion of soil-calcium could depress nodule formation only during the first day after inoculation. 相似文献
12.
This study describes the soil solution chemistry in the rhizosphere of fine roots of sessile oak ( Quercus petraea (M.) Liebl.)
grown in rhizotrons. A control was compared with soils treated with an equivalent CaCO3 of 1.4 t ha-1 CaO. Solution samples were extracted from the B-horizon using micro suction cups with a suction of ∼40 kPa. Two series of experiments were carried out: one irrigated with rain water (age of seedling 2 to 4 months) and one
irrigated with demineralized water (age of seedlings 1.5 to 2 months). Half of the sampling points were choosen close to the
roots and half in the bulk soil. In both experiments there was generally no rhizospheric gradient after liming. In contrast,
in the control, depletion in the rhizosphere occurred for most of the ions studied (Mg, Ca, Al, K, NO3
-, NH4
+, Cl-) in the demineralized water experiment, but this was different when rainwater was used. The latter effect is probably due
to the higher solution concentrations in the rainwater experiment but could also be a result of root damage due to low Ca/Al
ratios in the rhizosphere solution. It was concluded, that liming improved the chemical composition in the rhizosphere soil
solution by increasing overall solute concentration to levels enabling sufficient and easier nutrient uptake by roots.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
13.
Florence Devienne-Barret Céline Richard-Molard Michaël Chelle Olivier Maury Bertrand Ney 《Plant and Soil》2006,280(1-2):253-266
Studying Arabidopsis thaliana (L.) Heynh. root development in situ at the whole plant level without affecting shoot development has always been a challenge. Such studies are usually carried
out on individual plants, neglecting competition of a plant population, using hydroponic systems or Agar-filled Petri dishes.
Those both systems, however, present some limitations, such as difficulty to study precisely root morphogenesis or time-limited
culture period, respectively. In this paper, we present a method of Arabidopsis thaliana (L.) Heynh. cultivation in soil medium, named “Ara-rhizotron”. It allows the non-destructive study of shoot and root development
simultaneously during the entire period of vegetative growth. In this system, roots are grown in 2D conditions, comparable
to other soil cultures. Moreover, grouping several Ara-rhizotrons in a box enables the establishment of 3D shoot competition
as for plants grown in a population. In comparison to a control culture grown in pots in the same environmental conditions,
the Ara-rhizotron resulted in comparable shoot development in terms of dry mass, leaf area, number of leaves and nitrogen
content. We used this new culture system to study the effect of irrigation modalities on plant development. We found that
irrigation frequency only affected root partitioning in the soil and shoot nitrogen content, but not shoot or root growth.
These effects appeared at the end of the vegetative growth period. This experiment highlights the opportunity offered by the
Ara-rhizotron to point out tardy effects, affecting simultaneously shoot development and root architecture of plants grown
in a population. We discuss its advantages in relation to root development and physiology, as well as its possible applications. 相似文献
14.
Simultaneous X-ray imaging of plant root growth and water uptake in thin-slab systems 总被引:1,自引:0,他引:1
Direct and simultaneous observation of root growth and plant water uptake is difficult because soils are opaque. X-ray imaging techniques such as projection radiography or Computer Tomography (CT) offer a partial alternative to such limitations. Nevertheless, there is a trade-off between resolution, large field-of-view and 3-dimensionality: With the current state of the technology, it is possible to have any two. In this study, we used X-ray transmission through thin-slab systems to monitor transient saturation fields that develop around roots as plants grow. Although restricted to 2-dimensions, this approach offers a large field-of-view together with high spatial and dynamic resolutions. To illustrate the potential of this technology, we grew peas in 1 cm thick containers filled with soil and imaged them at regular intervals. The dynamics of both the root growth and the water content field that developed around the roots could be conveniently monitored. Compared to other techniques such as X-ray CT, our system is relatively inexpensive and easy to implement. It can potentially be applied to study many agronomic problems, such as issues related to the impact of soil constraints (physical, chemical or biological) on root development. 相似文献
15.
Influence of temperature and water potential on root growth of white oak 总被引:11,自引:0,他引:11
Root growth of white oak ( Quercus alba L.) was observed under field conditions using a rhizotron. The effects of temperature, soil water potential, and leaf water potential were evaluated on three measures of root growth and development: root elongation rate, number of growing roots, and root growth intensity (sum of projected root area compared to the total root viewing area). Root elongation rate was linearly related to changes in soil temperature and soil water potential. At soil temperatures less than 17deg;C, temperature was the dominant factor affecting rate of growth, bat at temperatures greater than 17°C soil water potential became the important factor. Unlike root elongation rate, the number of growing roots and root growth intensity increased at cold soil temperatures (8°C) and at soil water potentials of-0.3 to -0.8 MPa. At high soil water potentials (-0.1 MPa) root elongation rate reached a maximum while the number of growing roots and root growth intensity were low. These differences showed that root growth and development were not exclusively affected by the soil environment. In addition, the relationship between root growth and predawn leaf water potential suggested that root growth was a contributing factor to the drought resistance of white oak. 相似文献
16.
Since being built in 1990, the rhizotron facility in Wageningen, the Wageningen Rhizolab, has been used for experiments on crops (e.g. Alfalfa, Brussels sprouts, common velvet grass, field bean, fodder radish, leeks, lupins, maize, potato, beetroot, ryegrass, spinach, spring wheat, winter rye and winter wheat). In the experiments, horizontal glass minirhizotron tubes combined with auger sampling were used to assess rooting characteristics. For this paper we took the root data from these experiments and looked for a general relationship between thermal time/time after planting and rooting depth, the velocity of the root front and root proliferation. For certain depths (fixed by the depth at which the horizontal minirhizotrons were installed) a simple linear regression was established between the average root number per cm2 minirhizotron surface area and thermal time after planting. The compartments selected for each crop were those in which there had been a control treatment and/or in which conditions for rooting were considered to be optimal. We performed regression analyses per compartment and per depth, but only for the period after planting in which a linear increase of root numbers vs. thermal time was observed. After averaging the results, the regression procedure yielded two parameters of rooting for each crop: (a) the actual or thermal time at which the first root appeared at a certain depth and (b) the root proliferation rate after the first root had appeared. In this way, inherent crop differences in rooting behaviour (rooting depth and root proliferation) became apparent. For each crop, the velocity of the root front after planting could be established (calculated in cm(°C day)–1). This parameter differed greatly between crops. Some crops (such as leeks and common velvet grass) explored the soil profile slowly: the root front moved at a velocity of only 0.07cm(°C day)–1. Among the crops whose roots grew down much faster (0.18–0.26cm (°C day)–1) were cereals and fodder radish. For a day with an average temperature of 15°C these rates would have corresponded with the root front travelling approximately 1–4cm per day. In the crops studied the root front velocity did not correlate with the root proliferation rate. 相似文献
17.
Seasonal development of loblolly pine lateral roots in response to stand density and fertilization 总被引:1,自引:0,他引:1
In 1989, two levels each of stand density and fertilization treatments were factorially established in a 9-year-old loblolly pine plantation on a P-deficient Gulf Coastal Plain site in Rapides Parish, Louisiana, USA. In 1995, a second thinning was conducted on the previously thinned plots and fertilizer was re-applied to the previously fertilized plots. The morphology of new long lateral roots was evaluated at 2-week intervals in five Plexiglas rhizotrons per plot of two replications. The overall objective of this study was to evaluate the seasonal initiation of six morphological categories of long lateral roots ( 2.5 cm in length) in response to stand density and fertilization. Lateral root development exhibited a seasonal pattern with the initiation of branched lateral roots predominantly occurring in spring and summer. The initiation of non-branched lateral roots occurred throughout the year regardless of season. Stand density did not affect lateral root morphological development. However, fertilization stimulated the initiation of branched lateral roots that were greater than 1 mm in diameter. 相似文献
18.
A novel optical method for non-invasive, quantitative and high-resolution imaging of spatial and temporal pH dynamics in soils mediated by plant roots is introduced. This method overcomes present limitations of measurement of pH, mainly short-term and punctiform measurements, by recording long-term dynamics of the micro-pattern of pH in the root-soil interface without disturbance of the biological and physico-chemical conditions. Juncus effusus L., rooting in a permanently flooded rhizotron, was selected as the test organism for qualifying the technique. The measurements showed pronounced diurnal variations of pH along the roots, particularly along the elongation zone. Diurnal oscillation of pH caused by the roots reached up to 0.5 units. Long-term records at 4 s intervals over more than 8 weeks revealed considerable spatial and temporal patterns of pH dynamics in the rhizosphere of about 10% of the pH scale (pH 7.0-8.5). The measured data were validated by the use of pH electrodes. Concomitantly measured oxygen concentration showed hypoxic conditions around root tips (10-70 micromol O2 L-1) and almost anoxic conditions (0.9 micromol O2 L-1) in the bulk soil. The present study qualifies this novel pH-sensing technique as a powerful analytical tool for quantitative visualization of undisturbed bioprocess dynamics. 相似文献
19.
Javad Zamani Mohammad Ali Hajabbasi Ebrahim Alaie Mozhgan Sepehri Adrian Leuchtmann Rainer Schulin 《International journal of phytoremediation》2016,18(3):278-287
As the depth of soil petroleum contamination can vary substantially under field conditions, a rhizotron experiment was performed to investigate the influence of endophyte, P. indica, on maize growth and degradation of petroleum components in a shallow and a deep-reaching subsurface layer of a soil. For control, a treatment without soil contamination was also included. The degree in contamination and the depth to which it extended had a strong effect on the growth of the plant roots. Contaminated soil layers severely inhibited root growth thus many roots preferred to bypass the shallow contaminated layer and grow in the uncontaminated soil. While the length and branching pattern of these roots were similar to those of uncontaminated treatment. Inoculation of maize with P. indica could improve root distribution and root and shoot growth in all three contamination treatments. This inoculation also enhanced petroleum degradation in soil, especially in the treatment with deep-reaching contamination, consequently the accumulation of petroleum hydrocarbons (PAHs) in the plant tissues were increased. 相似文献
20.
Root demography in kiwifruit (Actinidia deliciosa) 总被引:5,自引:2,他引:3
A rhizotron was used to study fine-root demography in mature vines of kiwifruit (Actinidia deliciosa). The vines were grown in a deep, well drained, silt loam and received normal orchard management. Roots were measured from 10 to 160cm depth at biweekly intervals for 2 years. After an initial phase of rapid colonisation of the repacked soil behind the rhizotron windows, the total length of visible roots per vine remained quite steady. This apparent stability of the total belied fast and sustained localized turnover of the fine roots at all soil depths. Fifty-one per cent of the roots survived ≤28d, 69% died at an age ≤56d and only 8% survived >252d. For each year, the cumulative length of roots grown was equivalent to about 2·75 times the maximum net length of roots visible. These may be the largest annual rates of root turnover yet reported. This has important ramifications for the carbon balance, mineral nutrition and water relations of the plant. 相似文献