Anthony Trewavas
- Published in print:
- 2014
- Published Online:
- November 2014
- ISBN:
- 9780199539543
- eISBN:
- 9780191788291
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199539543.003.0014
- Subject:
- Biology, Plant Sciences and Forestry
The quotation that heads this chapter indicates the obvious relationship between advantage, intelligence and fitness. The well-known bending of some seedling roots to a displacement of the gravity ...
More
The quotation that heads this chapter indicates the obvious relationship between advantage, intelligence and fitness. The well-known bending of some seedling roots to a displacement of the gravity signal is considered. The anatomy of the root meristem is outlined and the mechanism of gravity sensing in the root cap columella, described. Auxin moves in seedling tissues in a polar manner and arrives in the root cap via the vascular tissue. In the cap it progresses shoot-wards in the tissues outside the vascular elements. The Cholodny-Went theory describes root bending as resulting from a redistribution of auxin on the two sides of a gravitropically-stimulated root. The recent molecular evidence that relates auxin to gravitropic bending is described. Some of this evidence which supports the Cholodny-Went theory is discussed and then critically examined. Other processes contribute to gravitropic responses than just auxin on its own and these can precede auxin redistribution. The sensitivity with which auxin acts to manipulate growth is discussed. There are also indications of complex growth control mechanisms from the individuality observed in root bending kinetics. There are at least two zones of gravitropic sensitivity in the root. The Cholodny-Went theory is an over-simplification of a group of mechanisms involved in growth orientation control. A complex soil environment will need equally complex mechanisms to control orientation if root systems work with optimal fitness. Potential contributions from other hormones and processes in the bending process might help explanation.Less
The quotation that heads this chapter indicates the obvious relationship between advantage, intelligence and fitness. The well-known bending of some seedling roots to a displacement of the gravity signal is considered. The anatomy of the root meristem is outlined and the mechanism of gravity sensing in the root cap columella, described. Auxin moves in seedling tissues in a polar manner and arrives in the root cap via the vascular tissue. In the cap it progresses shoot-wards in the tissues outside the vascular elements. The Cholodny-Went theory describes root bending as resulting from a redistribution of auxin on the two sides of a gravitropically-stimulated root. The recent molecular evidence that relates auxin to gravitropic bending is described. Some of this evidence which supports the Cholodny-Went theory is discussed and then critically examined. Other processes contribute to gravitropic responses than just auxin on its own and these can precede auxin redistribution. The sensitivity with which auxin acts to manipulate growth is discussed. There are also indications of complex growth control mechanisms from the individuality observed in root bending kinetics. There are at least two zones of gravitropic sensitivity in the root. The Cholodny-Went theory is an over-simplification of a group of mechanisms involved in growth orientation control. A complex soil environment will need equally complex mechanisms to control orientation if root systems work with optimal fitness. Potential contributions from other hormones and processes in the bending process might help explanation.
Christophe Godin, Eugenio Azpeitia, and Etienne Farcot
- Published in print:
- 2016
- Published Online:
- March 2016
- ISBN:
- 9780198752950
- eISBN:
- 9780191814426
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198752950.003.0009
- Subject:
- Physics, Soft Matter / Biological Physics
This chapter presents models of processes involved in the initiation and development of a flower. Models of hormonal transport are briefly described, focusing on two key aspects of floral ...
More
This chapter presents models of processes involved in the initiation and development of a flower. Models of hormonal transport are briefly described, focusing on two key aspects of floral development: initiation, due to the periodic local accumulation of auxin near the plant apex, and the genetic regulation of its development. Gene regulatory networks (GRNs) that control the initial steps of floral development and differentiation are investigated. In a simplified form, this network contains dozens of actors interacting with each other in space and time. The understanding of such a complex system requires a modeling approach in order to quantify these interactions and analyze their properties. The two main formalisms used to model GRNs are presented: the Boolean and ordinary differential equation formalisms. Throughout the chapter, specific mathematical topics of particular interest to the development of the ideas developed in the different sections are highlighted.Less
This chapter presents models of processes involved in the initiation and development of a flower. Models of hormonal transport are briefly described, focusing on two key aspects of floral development: initiation, due to the periodic local accumulation of auxin near the plant apex, and the genetic regulation of its development. Gene regulatory networks (GRNs) that control the initial steps of floral development and differentiation are investigated. In a simplified form, this network contains dozens of actors interacting with each other in space and time. The understanding of such a complex system requires a modeling approach in order to quantify these interactions and analyze their properties. The two main formalisms used to model GRNs are presented: the Boolean and ordinary differential equation formalisms. Throughout the chapter, specific mathematical topics of particular interest to the development of the ideas developed in the different sections are highlighted.
