tunica carpus theory
TRANSCRIPT
TUNICA CARPUS THEORY
Presented to : Mam TibaPresented by: Zeenat Meeran
GENERAL
Meristem: Divisible and unspecialized cell. Divided and become specialized in
relation to their function.
TYPE
Type Location function
Apical meristem
Tip of stems and roots
Growth: increase length at tip
Intercalary meristem
Between the tip and base stem and leaves
Growth: increase the length between the nodes
Laterlal meristem
Sides of stems and roots
Growth : increase in diameter
CHRACTERISTICS
Shape: Isodermatic ,spherical, oval or
polygonal. Arrangement:Compactly and lack intercellular space.
Dense cytoplasm, large distinct and prominent nucleous.
Have capacity to divide.
SHOOT APEX
Shoot apex- where new leaves and tissues of the stem arise
Theories about zonation of shoot apex: A. Apical cell theory B. Histogen theory C. Tunica-corpus theory
APICAL CELL THEORY
Hofmeister (1857) cell visible in early stages of
development and dividing like a single apical cell.
Nageli (1878) a single apical cell is structural
and functional unit, which governs the entire process of apical growth.
HISTOGEN THEORY
Henstein(1868) three distinct meristematic zones.Dermatogen: outermost and uniseriate layerPeriblem: middle region composed of
isodiamatric cell.Pelrome: central and inner massEach develop from independent group of initials
(histogens)
TUNICA CARPUS THEORY Schmidt, 1924 TUNICA and CORPUS 2 regions can be distinguished by their
plane of cell division Apices are best described by this
theory. This concept used to describe apical
structure of vegetative and floral part.
Dome like part of apical meristem have one to several outer layers.
Regularly arranged. Arise from specific group of initials. The tissue mass beneath the
superficial layers more random arrangement.
Tunica One to several layered Plane of division almost entirely
anticlincal
Carpus Central region Plane of division may be quit
randomlyTYPESA. Usual – 1. CMC 2. rib meristem 3. peripheral
B. Opuntia - + cambium-like transition zone
Central zone– (waiting meristem)- promeristem- corpus + portions of tunica - gives rise to:
Rib zone or pith rib meristem- below central zone; center location- becomes the pith
Peripheral zone or peripheral meristem- encircles the other zones- most meristematic (eumeristem)- densest protoplast and smallest dimensions- gives rise to leaf primordia, procambium, cortical ground tissue
Origin Evidences of surface layer in apex. Was deduced arrangement and
aspect of cell is fixed.
Satina et al.(1940):Two outer most layer of tunica Whereas third layer contributing cell to the carpus
Baker (1945):
Self-perpetuating tunica
No.38
Dermen (1945)
oxycoccus Distinct apical layer Histogenicaly independent
At was long thought that precilincal layers in th chimeras plant was not true tunica
Thiekle (1954-1957) Untrue Trandence spp. No preclinical division Elsewhere in surface layer
True tunica variable in number(1-9) Now recognized Parallel layer vary in number With ontogeny of plant With seasonal growth
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