PA
THE TISSUES Group of cell showing a common origin and usually performing a common function is called tissue.
Complex P
Meristematic tissues
Simple Permanent
1.
M
pM
Intercalary Meristem
Occurs between mature tissues Occurs in grasses, regenerate parts removed by grazing herbivores
I
I
I
CC
Parenchyma --Forms major component within organs -- Spherical, oval, round, polygonal or elongated in shape -- Thin walled, living -- Cellulosic cell wall ---- May have small intercellular spaces Functions (1) Storage (2) Secretion (3) Photosynthesis (if have chlorophyll)
P
Collenchyma --Occurs in layers below epidermis --Cells may be oval, spherical or polygonal in shape -- Thick walled, living m Corners of cell deposited with cellulose, hemicellulose and pectin --Intercellular space absent spaces Functions (1) Provide mechanical support to growing parts of plants (2) May perform photosynthesis (if cells contain chloroplast)
C
Sclerenchyma -- Long, narrow cells with thick lignified wall -- Dead Sclerenchyma fibre -- May be elongated and pointed Sclereids- -- May be spherical, oval or cylindrical (Common in fruits, nuts, pulp of guava, pear, etc.) Function: Mechanical support
S
(Four components) Tracheid --Elongated, tube like with tapering ends, lignified, dead and without protoplasm --Water transporting element Vessel --Long cylindrical tube, absent in gymnosperm --Multi celled, dead, devoid of protoplasm, Lignified with large central cavity -- Main water conducting element in angiosperms
X
Xylem Parenchyma --Living, thin walled --Involved in radial conduction of water, may store food Sclerenchyma Fibres Dead, lignified wall with obliteratedl umen.
X
Phloem (Four components) Sieve tube elements (Gymnosperms have sieve cells) - - Long, tube like, perforated end walls, lack nucleus at maturity --Peripheral cytoplasm with large central vacuole --- Transport of food material Companion cell (Gymnosperms have albuminous cells) --Specialised parenchyma cell, connected to sieve tubes by pit fields --Helps to maintain pressure gradient in sieve tubes. -- The functions of sieve tubes are controlled by the nucleus of companion cells.
P
Phloem (Four components) Phloem parenchyma --Elongated, tapering cylindrical cells --Stores food material, resin, mucilage, latex etc. --Absent in most of the monocots Bast fibres (Phloem fibres) --Elongated, sclerenchymatous, unbranched, pointed needle like apices -- Jute, flax and hemp produce commercial bast fibres. Generally absent in primary phloem but found in secondary phloem
P
E
STEM & ROOT SECTIONS
SECONDARY GROWTH
LEAF
B