Upload
jessie-heath
View
223
Download
1
Tags:
Embed Size (px)
Citation preview
Apical organizationApical organization
Organization in plants is dependent upon programmed, controlled cell division, followed by growth, further cell division and ultimately, differentiation.
Programmed and controlled cell division occurs within the domain of the vegetative apex.
the apexthe apex
All the tissues within the apex differentiate rapidly. By about 150 µm, cells within the apical region are starting to differentiate. In the pine apex (above), you can see developing leaflets.
The Coleus apex to the right, shows rapidly developing leaflets beneath the apical dome.
Cell divisionCell division
Cell division is responsible for the formation of all cells and tissues in the primary plant body as well as in the secondary plant body.
Cell source
apical and sub apical primary divisionapical and sub apical primary division
apical meristem
apical meristem
provascular tissue
provascular tissue
epidermisepidermis pithpith cortexcortexprimary phloem
primary phloem
primary xylem
primary xylem
ground meristem
ground meristemprotodermprotoderm
undifferentiated
generative source
Secondary celllineage
fascicular cambium
fascicular cambium
primary lineage
the secondary lineagethe secondary lineage
fascicular cambium
fascicular cambium
secondary xylem
secondary xylem
vascular cambium
vascular cambium
secondary phloem
secondary phloem
cork cambium
cork cambium
ASSOCIATED WITH THE VASCULAR BUNDLE ONLY
COMPLETE RING OF CAMBIUM
the secondary protective lineagethe secondary protective lineage
sub-epidermallayers
sub-epidermallayers
phellemphellem
phellogenphellogen
phelloderm
phelloderm
thecork cambium(bark layer)
click the periderm a protective barrier
Development of the peridermDevelopment of the periderm
sub-epidermallayers
sub-epidermallayers
phellemphellem
phellogenphellogen
phelloderm
phelloderm
The first periderm is formed just beneath the epidermis
phellem
phellogenphelloderm
a waterproof, fireproofinsulator
primary organizationprimary organization
groundmeristem
groundmeristem
PITHPITH CORTEXCORTEX
interfascicular
cambium
interfascicular
cambium
phellem/cork
cambium
phellem/cork
cambium
Click for Filling spaces notes
fascicular cambium
fascicular cambium
secondary xylem
secondary xylem
vascular cambium
vascular cambium
secondary phloem
secondary phloem
cork cambium
cork cambium
primary mechanical tissuesprimary mechanical tissues
groundmeristem
groundmeristem
PITHPITHCORTEXCORTEX
collenchymacollenchyma
sclerenchymasclerenchyma sclerenchymasclerenchyma
collenchyma(rare)
collenchyma(rare)
groundmeristem
groundmeristem
PITHPITH CORTEX
CORTEX
interfascicular
cambium
interfascicular
cambium
phellem/cork
cambium
phellem/cork
cambium
development of the vascular cambiumdevelopment of the vascular cambium
fascicular cambium
fascicular cambium
fusiform initials
fusiform initials
ray initials
ray initials
axialxylem
axialxylem
axial phloem
axial phloem
fascicular
cambium
fascicular
cambium
secondary
xylem
secondary
xylem
vascular cambium
vascular cambium
secondary
phloem
secondary
phloem
cork cambium
cork cambium
xylemrays
xylemrays
phloemrays
phloemrays
to cambial derivatives notes pages
cambial divisioncambial division
radial
axia
linitial
phloem
Cell division within the ray and fusiform initials results in the formation of derivative cells that are placed either on the outside of the mother cell, in which case they add to the secondary phloem (green cells), or on the inside endarch to) the mother cell, thus adding to the secondary xylem (blue cells).
xylem
Cell sourceCell source
The apical meristem is the principle source of new cells in the primary as well as within the secondary plant body. All cell division linked to vegetative growth, involves mitosis, and, as a result, the cells that are produced are exact copies of each other. Lineage depends on the position of the initial within the meristem.
the periderm a protective barrierthe periderm a protective barrier
During secondary growth, the diameter of stems and roots increases rapidly, which results in tension and splitting of the existing dermal tissues, which subsequently, will stretch and become disrupted.
The generative layer of the first periderm (phellogen) is initiated within parenchymatous elements in the outer cortex of stems and roots. It offers protection from invasion by insects, pathogens and fungi.
As the stem or root continues to increase in diameter, so successive peridems are formed. These are formed within the secondary phloem.
The periderm is a natural waterproof, fireproof insulator.
Filling spacesFilling spaces
Within all plants the primary packaging tissues are composed of cells that either fill in spaces, or support other areas of the stem, root or leaf. Thus, the parenchymatic elements that are produced (and have lineage back to the apical meristems) are produced from what is termed the ground meristem. In simple terms, the ground meristem is that region of a shoot or root apical meristem that is NOT involved in the production of vascular tissue.
cambial derivativescambial derivatives
The vascular cambium is the source of all need (secondary) differentiation in plants. It contains two systems, the secondary xylem, and the secondary phloem tissue. Each of these tissues is complex, and is developed and has evolved for specific functions – the xylem for th transport of water and water-soluble molecules, and the phloem for the transport of assimilated materials, which consist of sugars and related carbohydrates translocated in water.
Physiologically, the transport xylem is dead at maturity, has secondarily-lignified cell walls, and functions under extreme negative pressure potentials. Transport phloem on the other hand, contains a majority of living cells, with specialized sieve elements, which are geared for rapid, long-distance translocation of the assimilated carbohydrate pool. There transport elements, have thickened walls, are living at maturity and function under a high positive pressure potential.
click here for the next page
transport functionalitytransport functionality
The xylem and phloem conduits form axial tubes. These tubes facilitate rapid, long-distance movement of water and dissolved materials. It follows therefore that the fascicular cambial derivatives that form these transport cells are longer than they are wide, and that the cells will, depending on position form either xylem or phloem.
click here for cambial derivatives
click the need for lateral communication
back
the need for lateral communicationthe need for lateral communication
As the secondary plant body enlarges, so the carbohydrate conducting, and water transporting systems become laterally spatially and physiologically further removed from each other. The core of a stem or root, for example, may well contain a number of living cells, that not only require water, but a supply of assimilate and other carbohydrates, in order to maintain their functional state. If this does not happen or if the supply is cut off for some reason, then the core will die.
Lateral communication, and the production of these cells, is due o the activity of specialised cambial cells, called the ray cells. These cells are sort, often cubic in shape and the produce rows (files) of parenchymatous living cells, that interconnect the phloem with the inner xylem core, thereby facilitating exchange of carbohydrate inwards, and water outwards in the living plant.
Click to go back to the presentation