Question on part of seedling

[Vincent, Leszek]

Hi Pankaj,

This is one of those terms with a very variable definition - the
definition being dependent upon the taxon & context in which it is used.
For example the term "crown" is described as "The persistent base of a
herbaceous perennial" or "the top part of a tree"; or A synonym for the
"corona" (crown) of some flower structures (fide/according to Harris &
Harris); or "of the root, the point where root and stem meet" (fide
Jackson). 

In my ontology for Zea the terms "crown roots" & "subterranean crown
roots" are used - the term "crown" being used for the basal portion of
the growing stem/culm.

Below I've provided copy of the defns. for the terms "subterranean crown
roots" & "crown roots" which further demo. the context-specific use of
"crown" - you can skip the detail in these defns. - although it's
provided for context/illustration of use:

"subterranean crown roots": The subterranean crown roots are a component
of the adventitious root system. They are termed crown roots because
they originate from the basal portion of the growing stem/culm known as
the crown. The first subterranean crown roots (4-5), arranged in a
whorl, appear at the base of the second internode about as soon as the
tip of the coleoptile reaches the soil surface. A few of the subsequent
higher internodes may have a similar number of crown roots (in whorls),
after which the successive internodes have more and larger crown roots
up to 2-3 internodes above the soil surface. Note that the crown roots
above the soil surface (aerial) are frequently called 'brace' or 'prop'
roots. The crown roots emerge from the extreme base of the internode.
The subterranean crown roots produce numerous lateral adventitious roots
(see 'root branches')  early in their development. The crown roots
arising from internodes 2 to approximately 5 tend to grow horizontally
for some distance before turning downward. The crown roots from the base
of the higher internodes (appearing later in the growing season) grow
downward immediately after initiation.

"crown roots": There are two spatial components of the adventitious root
system. 1. A subterranean (below-ground) origin; 2. An aerial
(above-ground) origin. The subterranean adventitious roots are
frequently called crown roots because they originate from the basal
portion of the growing stem known as the crown. The first crown roots
(4-5), arranged in a whorl, appear at the base of the second internode
about as soon as the tip of the coleoptile reaches the soil surface. A
few of the subsequent higher internodes may have a similar number of
crown roots (in whorls), after which the successive internodes have more
and larger crown roots up to 2-3 internodes above the soil surface. Note
that the crown roots of the adventitious root system may appear to arise
from the nodes of the culm but careful inspection will reveal their
origin from the very base of the internode, frequently disrupting the
leaf sheath tissue that arises from the node immediately below the whorl
of crown roots. Those crown roots which are initially aerial in position
relative to the soil surface are termed 'brace' or 'prop' roots. Until
each prop root reaches the soil, it remains unbranched and relatively
rigid, and is usually covered by a mucilaginous substance that protects
the aerial part of the root from drying (desiccation). Note that once
the brace / prop roots enter the soil they produce numerous lateral
adventitious roots (see 'root branches'). The subterranean crown roots
produce numerous lateral adventitious roots early in their development.
The crown roots arising from internodes 2 to approximately 5 tend to
grow horizontally for some distance before turning downward. The crown
roots from the base of the higher internodes (appearing later in the
growing season) grow downward immediately after initiation.

- Leszek
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
P. Leszek D. Vincent Ph.D., FLS
Plant Science Unit, Dept. of Agronomy, 215 Curtis Hall,
University of Missouri-Columbia, Columbia, MO 65211-7020, USA.
Ph: (573) 884-3716 (Agronomy); Fax:(573) 884-7850;
Ph/Fax (Home): (573) 441-1228; 
Email: Leszek at missouri.edu
Yahoo! Messenger: leszekvincent
Plant Systematist on The Plant Ontology Consortium - NSF award 0321666
Associate Curator, Dunn-Palmer Herbarium (UMO)
Research Associate, Missouri Botanical Garden (MO), USA
CEO - PhytoSynergy, LLC
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*

> -----Original Message-----
> From: owner-po-dev at brie4.cshl.org 
> [mailto:owner-po-dev at brie4.cshl.org] On Behalf Of Pankaj Jaiswal
> Sent: Tuesday, October 14, 2003 2:21 PM
> To: POC-dev
> Subject: Question on part of seedling
> 
> 
> 
> Hi
> 
> Can somebody help me in identifying what is this term "crown" 
> stands for in 
> barley, described at http://bioinf.scri.sari.ac.uk/affy/mx-crown.htm
> 
> Thanks
> 
> Pankaj
> 
>