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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