Module 5 Flashcards
Parts of the “Bible” (5)
Apical Meristems
Primary Meristems
Primary Tissues
Secondary/Lateral Meristems
Secondary Tissues
What are the Apical Meristems
RAM and SAM
Apical Meristems become the Primary Meristems, what are they (3)
Protoderm
Ground Meristem
Procambium
Primary Tissue/s arising from the Protoderm
Epidermis
Primary Tissue/s arising from the Ground Meristem
Pith
Cortex
Endodermis
Mesophyll
Tissues arising from the Procambium
Primary: Pericycle, Primary Xylem, Primary Phloem
Secondary Meristem: Vascular Cambium
Secondary Meristems
Cork Cambium
Vascular Cambium
Cork Cambium is derived from?
Cortex, Epidermis, and Pericycle
Vascular Cambium is derived from?
Procambium and Pericycle
Secondary tissues
Periderm
Secondary Xylem
Secondary Phloem
embryonic tissue regions whose primary function is the formation of new cells
Meristems
Classification of
Meristems (Position)
Apical (SAM)
Intercalary
Lateral
Apical (RAM)
Located at the tips of root and shoot
Produces new leaves and flowers
Responsible for vertical
growth (primary growth)
Apical Meristems
Arranged parallel with
the root and stem axes
Produces bark on trees
Occurs at the cambium
Responsible for
horizontal growth
(secondary growth)
Lateral Meristems
Found within organs
near their bases
Situated between tissues that are no longer derived from apical meristem but meristematic activity occurs some distance from the apical
meristem
Increases length of internodes
Intercalary
Classification of Meristems (Origin)
Primary
Secondary
the initials are direct descendants of embryonic cells that never ceased their meristematic activity; apical meristems of shoot apex and root apex
Primary Meristem
the initials originate from cells that had differentiated then resumed meristematic activity
Secondary Meristem
Classification of Meristems (Continuity of activity)
Indeterminate
Determinate
Differentiate Indeterminate and Determinate
Indeterminate: Will keep growing
Determinate: Will stop growing
Gives rise to epidermal tissue system and develops into epidermis, stomata, and hairs
Protoderm
Gives rise to primary vascular tissues
Procambium
Gives rise to all tissues except epidermis and vascular tissues
Ground Meristem
Cytological characteristics of Meristematic cells (10)
- uniform in appearance
- usually small
- thin-walled (with flexible primary cell wall)
- isodiametric in shape
- large prominent nuclei
- have dense cytoplasm with numerous ribosomes
- have proplastids
- devoid of crystals and reserve materials
- vacuoles numerous, small or absent
- compact, lack intercellular space
the embryonic meristem
consists of apical initials (youngest
meristematic cells)
found at the tip of the SAM and RAM
some cells divide to form more initials, while others differentiate into primary meristems
least differentiated part of the apical meristem
Promeristem
Youngest Leaf Primordia is located where?
Look like “mandibles” of the “head”, “tenga ni batman”
90 degree phyllotaxy present in Coleus
Decussate
THEORIES ON SHOOT APICAL MERISTEM (SAM) ORGANIZATION
Apical Theory (Schmidt)
Histogen Theory (Hanstein)
Tunica-Corpus Theory (Schmidt)
A single apical cell is the structural and functional unit that governs the growth and development of the whole plant body
Apical Cell Theory
In Histogen Theory, the shoot apex comprises three distinct zones. What are these and what are their functions?
Dermatogen: Gives rise to epidermis
Periblem: Middle Layer giving rise to cortex
Plerome: Innermost layer giving rise to the steele
What are the modes of division of the different layers in Histogen theory?
Dermatogen: Anticlinal
Periblem: Both
Plerome: Periclinal
In Tunica-Corpus Theory, the shoot apex comprises two distinct zones. What are these and what are their functions?
Tunica: It is the peripheral zone of shoot apex, forms the epidermis; divides anticlinally; first 2 layers
Corpus: It is the inner zone of shoot apex that forms the cortex and stele of shoot; it divides in all directions (anticlinal and periclinal); third layer onwards
Division increasing width, side-to-side
Anticlinal
Division increasing length, Up and down
Periclinal
THEORIES ON ROOT APICAL MERISTEM (RAM) ORGANIZATION
Apical Cell Theory (Nageli)
Histogen Theory (Hanstein)
Korper Kappe Theory (Schuepp)
Quiescent Centre Concept (Clowes)
The single apical initial composes the root meristem tetrahedral in shade. It produces root cap from one
side and the remaining three sides produce the epidermis, cortex and vascular tissues
Apical Cell Theory
The histogen theory as applied to the RAM speaks of four zones in
the meristem, what are they and what are their functions?
Dermatogen: Outermost, gives rise to lateral root epidermis
Periblem: It is a middle layer, gives rise to cortex.
Plerome: It is innermost layer, gives rise to stele
Calyptrogen: It gives rise to root cap.
Equivalent to the tunica-corpus theory but for RAM instead of SAM.
Based on differences in the planes of cell division
The cells in the root apex divide in a pattern called T-divisions.
Korper Kappe Theory
Two zones off root apex according to Korper Kappe theory and their functions
Kappe: Cap
Korper: Body
T/F: Cells in Kappe zone divide first horizontally then lower daughter divides longitudinally (T-Division)
True
T/F: Cells in Korper zone, upper cells divide longitudinally (T-Division)
False, Kappe zone
States the apparently inactive quiescent centre region is the site of hormone synthesis and the ultimate source of all meristematic cells of the meristem
Quiescent Centre Concept
Observed in some gymnosperms and most angiosperms with 3 zones in the SAM
Cytohistological zonation (Foster)
3 Zones in Cytohistological Zonation
CMC or Central Mother Cell Zone
Rib or Pith Rib Zone
Peripheral or Flank Zone
Equivalent to promeristem containing tunica and corpus that has initials giving rise to rib and peripheral
CMC
Found below CMC becoming the central pith
Rib or Pith Rib
Found besides the rib zone and has rapidly dividing cells that gives rise to procambium, leaves and cortex
Peripheral or Flank Zone
Closed vs open root systems
Closed has visible layers of initials for steele, cortex and rootcap
Open has no distinct defined boundaries in RAM
Activity results in increase in the girth of the organ
Lateral/Secondary Meristems
collectively known as
the periderm
phellogen, cork (phellem) and phelloderm
forms a cylinder between xylem and phloem tissues
in x-sections, the cells of the vascular cambium look like flattened rectangles
Vascular Cambium
Two Cell Types
Fusiform initials
Ray initials
Vascular Cambium between the xylem and phloem (sandwiched)
Fascicular Cambium
Vascular Cambium not between the xylem and phloem
Interfascicular Cambium
Among initials, describe the appearance of the Fusiform and Ray
Fusiform: Long cells
Ray: Dotted circular cells
T/F: Vascular cambium divide anticlinally to
produce more cambial cells
True
T/F: Vascular cambium divide periclinally;
outer cell product
differentiates into
2 ̊ xylem, inner cell
product differentiate
into 2 ̊ phloem
False, Inner=xylem, Outer=Phloem
lateral meristem that produces the periderm
the layer that replaces the epidermis during secondary growth
may arise from the epidermis, cortex, phloem, and pericycle
outer product is the cork/phellem and inner product is the phelloderm
Cork Cambium
Describe appearance of the Periderm from outside in
Outer large cells: Phellem
Small thin flattened layer: Phellogen
Layer with circular cells: Phelloderm, slightly smaller and darker stained than cortex
