Incorporation of 3H-deoxynucleosides: changes in labelling indices during root development

1970 ◽  
Vol 48 (9) ◽  
pp. 1659-1663 ◽  
Author(s):  
R. D. MacLeod ◽  
D. Davidson
Keyword(s):  
Dna Synthesis ◽  
Root Development ◽  
Lateral Root ◽  
Developmental Stages ◽  
Root Systems ◽  
Interesting Aspect ◽  
Cell Cycles ◽  
Alternative Pathways ◽  
Dividing Cells

Whole root systems of Vicia faba were treated with 3H-TdR (tritiated deoxythymidine), 3H-AdR (tritiated deoxyadenosine), or 3H-CdR (tritiated deoxycytidine) solutions for 1 h. Labelling indices were determined immediately after treatment or up to 15 h later. Cells of lateral root meristems labelled immediately and most effectively with 3H-TdR. Lower levels of labelling were found in roots treated with 3H-AdR or 3H-CdR; these precursors, in particular 3H-CdR, appear to be unsuitable for the determination of any parameter of DNA synthesis. Cells of small primordia showed poor incorporation of labelled precursors immediately after a 1-h treatment but their labelling indices increased subsequently. It is suggested that pools of 3H-TdR and 3H-AdR are maintained and drawn upon by small primordia. Large primordia showed little or no incorporation of labelled precursors. The different responses of mitotically active cells taken from various developmental stages of a lateral root suggest that alternative pathways for the synthesis of DNA precursors are used to different extents during morphogenesis; the interesting aspect is that such changes can occur over a small number of cell cycles in a population of actively dividing cells.

DNA synthesis during the first stages of anterior regeneration in the polychaete annelid Owenia fusiformis (dedifferentiation and early phases of differentiation )

Development ◽  
1978 ◽  
Vol 44 (1) ◽  
pp. 81-92
Author(s):  
Monique Marilley ◽  
Yves Thouveny
Keyword(s):  
Dna Synthesis ◽  
Initial State ◽  
Cell Cycles ◽  
Small Areas ◽  
New Instrument ◽  
Dividing Cells ◽  
Marine Polychaete ◽  
The Moment ◽  
Early Phases ◽  
Anterior Regeneration

We have analysed DNA synthesis in early phases of regeneration in a marine Polychaete Annelid, Owenia fusiformis. The length and efficiency of the prereplicative phase was found to vary with the diurnal rhythm of activity of the animal; that is, it depends on the initial state of the cell population at the moment of the onset of proliferative stimulation. When animals were operated on at 12 a.m., the duration of the prereplicative phase of the first cells stimulated to proliferate was found to be 12 h. The remaining cells entered the S-phase progressively in waves until the 3rd day following amputation when nearly 100% of the blastema cells were stimulated. At that time the cell-cycles of these dividing cells were found to be highly synchronized. Blastema differentiation takes place on the 4th day and is initiated by stomodeum formation. During the differentiation phase, DNA synthesis is restricted to small areas of the regenerating part. The system described is viewed as a new instrument for investigating the control of the cell cycle in synchronized and subsequently differentiating tissue cells.

Pisolithus tinctorius forms long ectomycorrhizae and alters root development in seedlings of Pinus resinosa

1981 ◽  
Vol 59 (11) ◽  
pp. 2129-2134 ◽  
Author(s):  
Richard F. Sohn
Keyword(s):  
Growth Rate ◽  
Root Development ◽  
Lateral Root ◽  
Pinus Resinosa ◽  
Root Systems ◽  
Pisolithus Tinctorius ◽  
Third Order ◽  
Lateral Root Development ◽  
Mycorrhiza Formation

Ectomycorrhizae were synthesized on Pinus resinosa seedlings with Pisolithus tinctorius under aseptic, controlled environmental conditions. Root systems were harvested at 4, 6, and 15 weeks after seed germination. All roots were classified as either long or short and were examined for ectomycorrhiza development. Mycorrhizae were classified as "long mycorrhizae" or "short mycorrhizae," depending upon the type of root where infection occurred.Long mycorrhizae predominated at the early harvests and remained prominent at 15 weeks. A Hartig net of long mycorrhizae formed a morphological continuum from thin to thick. Negative correlations were observed between long mycorrhiza growth rate and the extent of infection. This suggests that a threshold growth rate exists below which mycorrhiza formation occurs readily, but above which mycorrhiza formation is progressively diminished. Relative to the controls, P. tinctorius inoculation increased the ratio of second- and third-order short roots to long roots. The role of host and fungus in controlling lateral root development is discussed.

Root mapping of three tropical pasture species using 32P

1969 ◽  
Vol 9 (39) ◽  
pp. 445 ◽  
Author(s):  
RA Bray ◽  
JB Hacker ◽  
DE Byth
Keyword(s):  
Root Growth ◽  
Root Development ◽  
Lateral Root ◽  
Sandy Loam ◽  
Lateral Roots ◽  
Root Systems ◽  
Growth Patterns ◽  
Constant Rate ◽  
Initial Root

Root growth patterns of Glycine javanica, Setaria anceps, and Medicago sativa were studied by uptake of 32P from a sandy loam. Placement of isotope was through permanently positioned PVC conduit on a grid over a 90� quadrant of the root system. Detection of radioactivity was in in situ plant material. Lucerne had strong initial root development but was slow to form lateral roots. Glycine and Setaria had quite similar root systems although Setaria had more rapid vertical root development than Glycine. Both these species had strong lateral root systems. When a regression of minimum root length against time was calculated, lateral root growth was shown to be independent of depth and distance from the plant, suggesting that roots behave as if growing from a point source in random directions at a constant rate. This rate was the same for all species. There were also indications of strong vertical root systems in lucerne and Setaria.

Dissecting mechanisms in root growth from the transition zone perspective

2020 ◽  
Vol 71 (8) ◽  
pp. 2390-2396 ◽  
Author(s):  
Elena Salvi ◽  
Riccardo Di Mambro ◽  
Sabrina Sabatini
Keyword(s):  
Arabidopsis Thaliana ◽  
Root Growth ◽  
Transition Zone ◽  
Root Development ◽  
Regulatory Networks ◽  
Developmental Stages ◽  
Dynamic Structure ◽  
Functional Domains ◽  
Dividing Cells ◽  
Plant Arabidopsis Thaliana

Abstract The root of the plant Arabidopsis thaliana is a dynamic structure in which cells continuously divide and differentiate to sustain its postembryonic undetermined growth. Cells at different developmental stages are organized in distinguished zones whose position and activities are maintained constant during root growth. In this review, we will discuss the latest discoveries on the regulatory networks involved in root zonation and, in particular, in the mechanisms involved in maintaining the position of the transition zone, a root developmental boundary. Developmental boundaries physically divide cells with different functions and identities. The transition zone separates dividing cells from differentiating cells in two functional domains, preserving their identity during root growth and thus controlling root development.

scholarly journals PLETHORA transcription factors orchestrate de novo organ patterning during Arabidopsis lateral root outgrowth

2017 ◽  
Vol 114 (44) ◽  
pp. 11709-11714 ◽  
Author(s):  
Yujuan Du ◽  
Ben Scheres
Keyword(s):  
Transcription Factors ◽  
Lateral Root ◽  
De Novo ◽  
Stage Ii ◽  
Lateral Root Primordia ◽  
Growth Axis ◽  
Cell Divisions ◽  
Dividing Cells ◽  
Response Gradient

Plant development is characterized by repeated initiation of meristems, regions of dividing cells that give rise to new organs. During lateral root (LR) formation, new LR meristems are specified to support the outgrowth of LRs along a new axis. The determination of the sequential events required to form this new growth axis has been hampered by redundant activities of key transcription factors. Here, we characterize the effects of three PLETHORA (PLT) transcription factors, PLT3, PLT5, and PLT7, during LR outgrowth. In plt3plt5plt7 triple mutants, the morphology of lateral root primordia (LRP), the auxin response gradient, and the expression of meristem/tissue identity markers are impaired from the “symmetry-breaking” periclinal cell divisions during the transition between stage I and stage II, wherein cells first acquire different identities in the proximodistal and radial axes. Particularly, PLT1, PLT2, and PLT4 genes that are typically expressed later than PLT3, PLT5, and PLT7 during LR outgrowth are not induced in the mutant primordia, rendering “PLT-null” LRP. Reintroduction of any PLT clade member in the mutant primordia completely restores layer identities at stage II and rescues mutant defects in meristem and tissue establishment. Therefore, all PLT genes can activate the formative cell divisions that lead to de novo meristem establishment and tissue patterning associated with a new growth axis.

Lateral root formation and nutrients: nitrogen in the spotlight

2021 ◽  
Author(s):  
Pierre-Mathieu Pélissier ◽  
Hans Motte ◽  
Tom Beeckman
Keyword(s):  
Signaling Pathways ◽  
Root System ◽  
Root Development ◽  
Lateral Root ◽  
Molecular Mechanisms ◽  
Root Formation ◽  
Lateral Roots ◽  
Nutrient Use Efficiency ◽  
Lateral Root Formation ◽  
Lateral Root Development

Abstract Lateral roots are important to forage for nutrients due to their ability to increase the uptake area of a root system. Hence, it comes as no surprise that lateral root formation is affected by nutrients or nutrient starvation, and as such contributes to the root system plasticity. Understanding the molecular mechanisms regulating root adaptation dynamics towards nutrient availability is useful to optimize plant nutrient use efficiency. There is at present a profound, though still evolving, knowledge on lateral root pathways. Here, we aimed to review the intersection with nutrient signaling pathways to give an update on the regulation of lateral root development by nutrients, with a particular focus on nitrogen. Remarkably, it is for most nutrients not clear how lateral root formation is controlled. Only for nitrogen, one of the most dominant nutrients in the control of lateral root formation, the crosstalk with multiple key signals determining lateral root development is clearly shown. In this update, we first present a general overview of the current knowledge of how nutrients affect lateral root formation, followed by a deeper discussion on how nitrogen signaling pathways act on different lateral root-mediating mechanisms for which multiple recent studies yield insights.

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