Soil strength and rate of root elongation alter the accumulation of Pseudomonas spp. and other bacteria in the rhizosphere of wheat

2003 ◽  
Vol 30 (5) ◽  
pp. 483 ◽  
Author(s):  
Michelle Watt ◽  
Margaret E. McCully ◽  
John A. Kirkegaard
Keyword(s):  
Root Elongation ◽  
Root Hairs ◽  
Elongation Rate ◽  
Root Tip ◽  
Controlled Environment ◽  
Root Tips ◽  
Pseudomonas Spp ◽  
Root Elongation Rate ◽  
Slow Growing ◽  
Total Bacteria

Results from a controlled environment system and the field showed that slow root elongation rate was associated with accumulation of Pseudomonas spp. in the rhizosphere; fast root elongation avoided accumulation. In the controlled environment system, total bacteria and bacteria belonging to the genus Pseudomonas were quantified along wheat (Triticum aestivum L. cv. Janz) seminal roots elongating at rates of 2.4 or 0.8 cm d–1 in loose and compacted field soil, respectively. Although total numbers of bacteria were similar for both rates of elongation, more Pseudomonas spp. accumulated on the slow-growing roots and their numbers were greatest 0.5–1 cm from the root tips. A reduced rate of root elongation in compacted soil accelerated the differentiation of root hairs, branch roots and adhesion of rhizosheath soil. Elongation rate and distance between the root tip and the zone of root hair development were positively correlated (r=0.9), providing a morphological indicator of root elongation rate in the field. Slow-growing roots from the field had 20 times more Pseudomonas spp. per unit root length than fast-growing field roots, while total bacteria were 8-fold higher; differences were greatest 0–1 cm from the tips. These results may explain how soil structure and Pseudomonas spp. interact in conservation farming. Rapid root elongation is identified as a desirable trait for avoiding accumulations of bacteria.

scholarly journals Root Tip Shape Governs Root Elongation Rate under Increased Soil Strength

2017 ◽  
Vol 174 (4) ◽  
pp. 2289-2301 ◽  
Author(s):  
Tino Colombi ◽  
Norbert Kirchgessner ◽  
Achim Walter ◽  
Thomas Keller
Keyword(s):  
Root Elongation ◽  
Soil Strength ◽  
Elongation Rate ◽  
Root Tip ◽  
Root Elongation Rate

Responses of root systems of young Pinussylvestris and Piceaabies plants to water deficits and soil acidity

1987 ◽  
Vol 17 (8) ◽  
pp. 805-812 ◽  
Author(s):  
N. Bartsch
Keyword(s):  
Root Elongation ◽  
Mineral Soil ◽  
Root Hairs ◽  
Root Systems ◽  
Elongation Rate ◽  
Test Duration ◽  
Water Deficits ◽  
Root Parameters ◽  
Root Elongation Rate ◽  
Normal Acidity

Responses of the root systems of two conifer species (Pinussylvestris L. and Piceaabies (L.) Karst.) in a strongly acidic mineral soil and in a soil with normal acidity to increasing water deficits and subsequent rewatering were examined in a growth chamber experiment. Two-year-old greenhouse seedlings were transplanted into transparent acrylic containers (rhizotrons) positioned at an angle of 45° in wooden boxes. During the 12-week test duration, the following root parameters were measured in intervals of 2 to 4 days: root elongation rate, number of growing roots, root diameter, development of root hairs, root browning, and the development of mycorrhizae. The test plants, the spruces more so than the pines, in the strongly acidic soil were limited in their ability to react to changes of the water supply. Of the examined root parameters, the root elongation rate and the number of growing roots showed the most distinct reactions.

Primary Root Elongation Rate and Abscisic Acid Levels of Maize in Response to Water Stress

Crop Science ◽  
2011 ◽  
Vol 51 (1) ◽  
pp. 157-172 ◽  
Author(s):  
Kristen A. Leach ◽  
Lindsey G. Hejlek ◽  
Leonard B. Hearne ◽  
Henry T. Nguyen ◽  
Robert E. Sharp ◽  
...  
Keyword(s):  
Abscisic Acid ◽  
Water Stress ◽  
Root Elongation ◽  
Primary Root ◽  
Elongation Rate ◽  
Root Elongation Rate ◽  
Response To Water

scholarly journals Modelling time variations of root diameter and elongation rate as related to assimilate supply and demand

2020 ◽  
Vol 71 (12) ◽  
pp. 3524-3534
Author(s):  
Loïc Pagès ◽  
Marie Bernert ◽  
Guillaume Pagès
Keyword(s):  
Root System ◽  
Root Elongation ◽  
Lateral Roots ◽  
Supply And Demand ◽  
Root System Architecture ◽  
Elongation Rate ◽  
Growth Patterns ◽  
Root Tip ◽  
Generic Model ◽  
Maximal Diameter

Abstract In a given root system, individual roots usually exhibit a rather homogeneous tip structure although highly different diameters and growth patterns, and this diversity is of prime importance in the definition of the whole root system architecture and foraging characteristics. In order to represent and predict this diversity, we built a simple and generic model at root tip level combining structural and functional knowledge on root elongation. The tip diameter, reflecting meristem size, is used as a driving variable of elongation. It varies, in response to the fluctuations of photo-assimilate availability, between two limits (minimal and maximal diameter). The elongation rate is assumed to be dependent on the transient value of the diameter. Elongation stops when the tip reaches the minimal diameter. The model could satisfactorily reproduce patterns of root elongation and tip diameter changes observed in various species at different scales. Although continuous, the model could generate divergent root classes as classically observed within populations of lateral roots. This model should help interpret the large plasticity of root elongation patterns which can be obtained in response to different combinations of endogenous and exogenous factors. The parameters could be used in phenotyping the root system.

Histopathology of Pythium infected strawberry roots

1972 ◽  
Vol 50 (5) ◽  
pp. 1091-1096 ◽  
Author(s):  
S. Nemec
Keyword(s):  
Root Hairs ◽  
Petri Dish ◽  
Root Tip ◽  
Test Results ◽  
Root Tips ◽  
Cortical Cells ◽  
Pythium Irregulare ◽  
Infected Root ◽  
Cortical Infection ◽  
Host Parasite

Host–parasite interactions between eight Pythium species, previously isolated from necrotic strawberry root tissue, and Fragaria × ananassa Duch. runner plant main roots were studied. When excised roots were placed in water on petri dish cultures, P. rostratum and P. hypogenum infection was limited to the root tip epidermis. Pythium irregulare, P. perniciosum, P. dissotocum, P. sylvaticum, P. ultimum, and unidentified isolate 1E penetrated the epidermis several centimeters along the zone of maturation. Penetration occurred most frequently through root hairs by hyphae; resulting infections usually stopped in the epidermis or adjacent cortex, and here hyphae formed sporangium-like structures, oogonia, and oospores. Extensive cortical infection by hyphae was primarily limited to the zone of elongation. Extent of epidermal and cortical infection in roots grown in soil with P. irregulare, P. dissotocum, and P. sylvaticum was similar to petri dish test results. Stelar infection by P. sylvaticum and P. dissotocum occurred mainly in phloem cells, but did not advance far into the region of maturation. Numerous oogonia formed in infected steles and usually in adjacent cortical cells. Infected roots ranged from a white to grey, water-soaked color. Extensively infected root tips typically were unhealthy, succulent, and thin.

scholarly journals Alleviation of Al toxicity by Si is associated with the formation of Al-Si complexes in root tissues of sorghum

2017 ◽  
Author(s):  
Peter M. Kopittke ◽  
Alessandra Gianoncelli ◽  
George Kourousias ◽  
Kathryn Green ◽  
Brigid A. McKenna
Keyword(s):  
Cross Sections ◽  
Root Elongation ◽  
Elongation Rate ◽  
In Planta ◽  
X Ray ◽  
Root Elongation Rate ◽  
Root Tissues ◽  
Wall Loosening ◽  
Nutrient Solutions

AbstractSilicon is reported to reduce the toxic effects of Al on root elongation but the in planta mechanism by which this occurs remains unclear. Using seedlings of soybean (Glycine max) and sorghum (Sorghum bicolor), we examined the effect of up to 2 mM Si on root elongation rate (RER) in Al-toxic nutrient solutions. Synchrotron-based low energy X-ray fluorescence (LEXRF) was then used for the in situ examination of the distribution of Al and Si within cross-sections cut from the apical tissues of sorghum roots. The addition of Si potentially increased RER in Al-toxic solutions, with RER being up to ca. 0.3 mm h−1 (14 %) higher for soybean and ca. 0.2 mm h−1 (17 %) higher for sorghum relative to solutions without added Si. This improvement in RER could not be attributed to a change in Al-chemistry of the bulk nutrient solution, nor was it due to a change in the concentration of Al within the apical (0-10 mm) root tissues. Using LEXRF to examine sorghum, it was demonstrated that in roots exposed to both Al and Si, much of the Al was co-located with Si in the mucigel and outer apoplast. These observations suggest that Si reduces the toxicity of Al in planta through formation of Al-Si complexes in mucigel and outer cellular tissues, thereby decreasing the binding of Al to the cell wall where it is known to inhibit wall loosening as required for cell elongation.

scholarly journals Influence of Day and Night Temperature Differentials on Root Elongation Rate, Root Hydraulic Properties, and Shoot Water Relations in Chrysanthemum

2000 ◽  
Vol 125 (3) ◽  
pp. 383-389
Author(s):  
Pauline Helen Kaufmann ◽  
Robert J. Joly ◽  
P. Allen Hammer
Keyword(s):  
Root Elongation ◽  
Dark Period ◽  
Stem Elongation ◽  
Elongation Rate ◽  
Light Period ◽  
Night Temperature ◽  
Diurnal Patterns ◽  
Root Elongation Rate ◽  
Temperature Regimes ◽  
Maximum Root

The difference between night and day temperature (DIF = day - night temperature) has been shown to affect plant height. A positive DIF (+DIF), cooler night than day temperature, increases stem elongation while a negative DIF (- DIF), warmer night than day temperature, decreases stem elongation. The physiological mechanism underlying the growth response to DIF is not understood, however, and the effects of day/night temperature differentials on root permeability to water and root elongation rate have not been studied. The objective of this study was to describe how +DIF and -DIF temperature regimes affect leaf water relations, root water flux (Jv), root hydraulic conductivity (Lp), and root elongation rates of `Boaldi' chrysanthemum [Dendranthema ×grandiflora Kitam. `Boaldi' (syn. Chrysanthemum ×morifolium Ramat.)] plants over time. Leaf turgor pressure (ψp) was 0.1 to 0.2 MPa higher in plants grown in a +6 °C DIF environment throughout both the light and dark periods, relative to those in a -6 °C DIF environment. Jv differed markedly in roots of plants grown in +DIF vs. -DIF environments. Rhythmic diurnal patterns of Jv were observed in all DIF treatments, but the relative timing of flux minima and maxima differed among treatments. Plants grown in positive DIF regimes exhibited maximum root flux at the beginning of the light period, while those in negative DIF environments had maximum root flux during the first few hours of the dark period. Plants grown in +DIF had significantly higher Lp than -DIF plants. Plants grown in +DIF and -DIF environments showed differences in the diurnal rhythm of root elongation. During the dark period, +DIF plants exhibited minimal root elongation rates, while -DIF plants exhibited maximal rates. During the light period, the converse was observed. In -DIF temperature regimes, periods of rapid root elongation coincided with periods of high Jv. Results of this study suggest that negative DIF environments lead to leaf turgor reductions and markedly alter diurnal patterns of root elongation. These changes may, in turn, act to reduce stem elongation.

scholarly journals Supra-physiological levels of Gibberellins/DELLAs alter the patterning, morphology and abundance of root hairs in root tips of A. thaliana seedlings

2021 ◽  
Author(s):  
Iva McCarthy-Suarez
Keyword(s):  
Gene Expression ◽  
Cell Fate ◽  
Epidermal Cell ◽  
Root Hair ◽  
Root Hairs ◽  
Root Tip ◽  
Spatial Patterning ◽  
Root Tips ◽  
Root Epidermis

In spite of the known role of gibberellins (GAs), and of their antagonistic proteins, the DELLAs, in leaf hair production, no investigations, however, have assessed their hypothetical function in the production of root hairs. To this aim, the effects of supra-physiological levels of GAs/DELLAs on the spatial patterning of gene expression of the root hair (CPC) and root non-hair (GL2, EGL3 and WER) epidermal cell fate markers, as well as on the distribution, morphology and abundance of root hairs, were studied in root tips of 5-day-old A. thaliana seedlings. Results showed that excessive levels of GAs/DELLAs impaired the spatial patterning of gene expression of the root hair/non-hair epidermal cell fate markers, as well as the arrangement, shape and frequency of root hairs, giving rise to ectopic hairs and ectopic non-hairs, two-haired cells, two-tipped hairs, branched hairs, longer and denser hairs near the root tip under excessive DELLAs, and shorter and scarcer hairs near the root tip under excessive GAs. However, when the gai-1 (GA-insensitive-1) DELLA mutant protein was specifically over-expressed at the root epidermis, no changes in the patterning or abundance of root hairs occurred. Thus, these results suggest that, in seedlings of A. thaliana, the GAs/DELLAs might have a role in regulating the patterning, morphology and abundance of root hairs by acting from the sub-epidermal tissues of the root.

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