Influence de la sécheresse sur la morphologie du système racinaire du Carex setifolia

1977 ◽  
Vol 55 (9) ◽  
pp. 1236-1245 ◽  
Author(s):  
S. Da ◽  
C. Hubac ◽  
N. Vartanian
Keyword(s):  
Root Growth ◽  
Water Deficit ◽  
Lateral Root ◽  
Histological Study ◽  
Root Tip ◽  
Root Initiation ◽  
Cultural Conditions ◽  
Aerial Parts ◽  
Lateral Root Initiation ◽  
The Difference

Two kinds of roots, differing in width, can be grown from the regularly watered rhizome of Carex setifolia in strict cultural conditions. When plants are subjected to drought, which increases water deficit in the plants, root growth stops and the root tip necroses while lateral root initiation is stimulated. After watering again, growth of aerial parts is resumed, either from the oldest tiller after moderate desiccation, or from new tillers. The roots with the greatest diameter show an increase in thickness just behind the tip. The thickening lasts only 48 h after the beginning of watering, then roots grow normally again. Sometimes, several roots initiate from the thickened portion of the tuberized zone.An histological study of the normal roots and tuberized zones indicates that the difference occurs in the cortex. Whereas the cortex is lacunar in normal roots, it looks dense in tuberized parts of the roots and consists of radial rows of cells apparently generated from an extra-endodermic layer. This generative zone is normally present, though undeveloped and nonfunctional in normal roots of C. setifolia. Furthermore, a large amount of starch is found in the cortex of the thickened parts of the roots.

A histological study of lateral root initiation and development inZea mays

PROTOPLASMA ◽  
1970 ◽  
Vol 70 (2) ◽  
pp. 179-205 ◽  
Author(s):  
J. K. Bell ◽  
Margaret E. McCully
Keyword(s):  
Lateral Root ◽  
Histological Study ◽  
Root Initiation ◽  
Lateral Root Initiation

Application of Phytohormones to Pea Roots After Removal of the Apex: Effect on Lateral Root Production

1979 ◽  
Vol 6 (2) ◽  
pp. 195 ◽  
Author(s):  
PB Goodwin ◽  
SC Morris
Keyword(s):  
Lateral Root ◽  
Lateral Roots ◽  
Primary Root ◽  
Root Production ◽  
Root Tip ◽  
Naphthaleneacetic Acid ◽  
Root Initiation ◽  
Lateral Root Initiation ◽  
Lateral Bud ◽  
Bud Growth

Removal of 2 mm of the primary root tip of Pisum sativum caused a complete halt to primary root elongation, but did not alter the total number of laterals formed. The auxins indole-3-acetic acid and 1-naphthaleneacetic acid, when applied to the stump in a lanolin emulsion, increased the number of lateral roots. High levels of abscisic acid and low levels of the cytokinins N6-benzylaminopurine and N6-(γ, γ-dimethylallylamino)purine, and of the gibberellins GA3 and GA7, resulted in decreased lateral root production. Kinetin was without effect. There appears to be an inverse relationship between auxins and cytokinins in root/shoot growth coordination. Auxins, which are produced in the shoot tip, inhibit lateral bud growth but promote lateral root initiation. Cytokinins, which are produced in the root tip, inhibit lateral root initiation, but promote lateral stem growth.

Differential uptake and toxicity of ionic and chelated copper in Triticum aestivum

1985 ◽  
Vol 63 (7) ◽  
pp. 1271-1275 ◽  
Author(s):  
Gregory J. Taylor ◽  
Charles D. Foy
Keyword(s):  
Triticum Aestivum ◽  
Root Growth ◽  
Toxic Effect ◽  
Lateral Root ◽  
Fe Deficiency ◽  
Root Initiation ◽  
Nutrient Deficiencies ◽  
Lateral Root Initiation ◽  
Leaf Tissues ◽  
Root Tissues

Plants of Triticum aestivum L. cv. Atlas-66 were grown in nutrient solutions containing 0–50 μM Cu as CuSO4 or 0–800 μM Cu as Cu-EDTA to compare the toxic effects of ionic and chelated Cu when yield reductions were similar in magnitude. Plants exposed to 50 μM CuSO4 accumulated 43 ± 6 μg g−1 Cu in leaf tissues and 2300 ± 130 μg g−1 in root tissues. Plants injured by CuSO4 showed acute signs of Cu toxicity; leaves showed mild necrosis and symptoms of induced Fe deficiency and root growth and lateral root initiation were inhibited. Concentrations of Fe, Mn, and Mg in leaves of plants injured by CuSO4 were low, possibly leading to nutrient deficiencies. Concentrations of Ca in leaves were also low, but were above levels considered to be deficient. Plants exposed to 800 μM Cu-EDTA accumulated 260 ± 7 μg g−1 Cu in leaf tissues and 6600 ± 1200 μg g−1 Cu in root tissues. Despite higher tissue concentrations of Cu, plants injured by Cu-EDTA showed systemic toxicity symptoms, possibly reflecting induced Fe deficiency as the primary toxic effect. Leaves of plants injured by Cu-EDTA showed mild necrosis and symptoms of induced Fe deficiency, root growth was depressed (but to a lesser extent than with CuSO4), and lateral root initiation was unaffected. Concentrations of Fe in leaves of plants injured by Cu-EDTA were lower than plants grown with micronutrient levels of Cu, while concentrations of Mn, Ca, and Mg in leaves of Cu-EDTA injured plants were higher. Differential toxicity of CuSO4 and Cu-EDTA could occur if Cu-EDTA were absorbed across the plasma membrane as an intact complex or if the primary toxic effect of CuSO4 and Cu-EDTA were on membrane structure and (or) function.

Root growth in corn and soybeans: effects of cadmium and lead on lateral root initiation

1978 ◽  
Vol 56 (3) ◽  
pp. 277-281 ◽  
Author(s):  
Carl P. Malone ◽  
Raymond J. Miller ◽  
D. E. Koeppe
Keyword(s):  
Root Growth ◽  
Lateral Root ◽  
Lateral Roots ◽  
Toxic Effects ◽  
Root Initiation ◽  
Inhibitory Effects ◽  
Lateral Root Initiation ◽  
Primary Roots ◽  
Cadmium And Lead

This study examines the previously reported inhibitory effects of Cd on root growth. In hydroponic experiments, 100 μg Cd/ℓ effected a 33% inhibition of lateral root initiation of corn. The growth of corn and soybean primary roots was not reduced at Cd concentrations of 1 mg/ℓ, and the number of lateral root initials in soybeans was not reduced at 2 mg Cd/ℓ. The toxic effects of Cd were ameliorated by additions of Zn or by additions of Fe citrate to nutrient growth solutions. While both Zn and Fe additions did result in increased lateral root initiation, the number of initials was significantly lower than the controls. Lead had no effect on the initiation of soybean lateral roots at a concentration of 100 μg Pb/ℓ. However, 5 mg Pb/ℓ did effect a 21% decrease in corn lateral root initials, but this decrease could not be demonstrated with higher Pb concentrations.

scholarly journals Phloem-associated auxin response maxima determine radial positioning of lateral roots in maize

2012 ◽  
Vol 367 (1595) ◽  
pp. 1525-1533 ◽  
Author(s):  
Leentje Jansen ◽  
Ianto Roberts ◽  
Riet De Rycke ◽  
Tom Beeckman
Keyword(s):  
Lateral Root ◽  
Vascular Tissue ◽  
Lateral Roots ◽  
Root Tip ◽  
Root Initiation ◽  
Auxin Response ◽  
Lateral Root Initiation ◽  
Evolutionarily Conserved ◽  
Chemical Inhibition ◽  
Pericycle Cells

In Arabidopsis thaliana , lateral-root-forming competence of pericycle cells is associated with their position at the xylem poles and depends on the establishment of protoxylem-localized auxin response maxima. In maize, our histological analyses revealed an interruption of the pericycle at the xylem poles, and confirmed the earlier reported proto-phloem-specific lateral root initiation. Phloem-pole pericycle cells were larger and had thinner cell walls compared with the other pericycle cells, highlighting the heterogeneous character of the maize root pericycle. A maize DR5::RFP marker line demonstrated the presence of auxin response maxima in differentiating xylem cells at the root tip and in cells surrounding the proto-phloem vessels. Chemical inhibition of auxin transport indicated that the establishment of the phloem-localized auxin response maxima is crucial for lateral root formation in maize, because in their absence, random divisions of pericycle and endodermis cells occurred, not resulting in organogenesis. These data hint at an evolutionarily conserved mechanism, in which the establishment of vascular auxin response maxima is required to trigger cells in the flanking outer tissue layer for lateral root initiation. It further indicates that lateral root initiation is not dependent on cellular specification or differentiation of the type of vascular tissue.

Formation of lateral root meristems is a two-stage process

Development ◽  
1995 ◽  
Vol 121 (10) ◽  
pp. 3303-3310 ◽  
Author(s):  
M.J. Laskowski ◽  
M.E. Williams ◽  
H.C. Nusbaum ◽  
I.M. Sussex
Keyword(s):  
Lateral Root ◽  
Lateral Roots ◽  
Initial Period ◽  
Subsequent Stage ◽  
Root Initiation ◽  
Root Meristems ◽  
Lateral Root Initiation ◽  
Cell Layers ◽  
Stage Process ◽  
Pericycle Cells

In both radish and Arabidopsis, lateral root initiation involves a series of rapid divisions in pericycle cells located on the xylem radius of the root. In Arabidopsis, the number of pericycle cells that divide to form a primordium was estimated to be about 11. To determine the stage at which primordia are able to function as root meristems, primordia of different stages were excised and cultured without added hormones. Under these conditions, primordia that consist of 2 cell layers fail to develop while primordia that consist of at least 3–5 cell layers develop as lateral roots. We hypothesize that meristem formation is a two-step process involving an initial period during which a population of rapidly dividing, approximately isodiametric cells that constitutes the primordium is formed, and a subsequent stage during which meristem organization takes place within the primordium.

scholarly journals Interacting Glutamate Receptor-Like Proteins in Phloem Regulate Lateral Root Initiation in Arabidopsis

2013 ◽  
Vol 25 (4) ◽  
pp. 1304-1313 ◽  
Author(s):  
Eric D. Vincill ◽  
Arielle E. Clarin ◽  
Jennifer N. Molenda ◽  
Edgar P. Spalding
Keyword(s):  
Glutamate Receptor ◽  
Lateral Root ◽  
Root Initiation ◽  
Lateral Root Initiation
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