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Anatomy of Flowering Plants

Secondary Growth
Secondary growth is absent in monocotyledons, but present in dicots
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Vascular cambium
Intrafascicular cambium- The cells of cambium present between primary xylem and
primary phloem
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Cambial ring then cut off new cells to form secondary xylem (towards pith) and
secondary phloem (towards periphery)
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Autumn wood (late wood): Cambium is less active and forms less number of xylary
elements with narrow vessels
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These rings are used to estimate the age of tree
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Sapwood helps in conduction of water and minerals from root to leaves
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Phellogen, phellem, and phelloderm are collectively known as periderm
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Lenticels – help in exchange of gases

Tissue
It is a group of cells that are similar in structure and are organised together to perform
a specific function
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The examples include root tip, shoot tip, and base of the leaves
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Apical meristem: They are present in the growing tips of stems and roots
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Intercalary meristem: They lie at the base of leaves or internodes
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Lateral meristem: They lie on the lateral sides of the stem and root
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Therefore, they are called primary meristems
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Hence, they are known as secondary meristem
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All these cells
work in coordinated manner to perform one common function
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Tracheids and vessels are long tube-like structures with thick walls and tapering
ends
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Function: to transport water and minerals vertically
Xylem fibre is made up of dead cells
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Function: Storage of food and helps in radial conduction of water
Phloem:
It transports food material from leaves to different parts of the plant
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Function: to transport food material
Companion cells are specialised parenchymatous cells, closely associated with
sieve tube elements
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Function: to maintain the pressure gradient in sieve tubes
Phloem parenchyma is composed of living cells that help in storage of food
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Tissue System
Epidermal tissue system:
It comprises of epidermal cells, stomata, trichomes, and hairs
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Cuticle is the waxy layer present outside the
epidermis
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It is absent in roots
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Root hair helps in absorption of water and mineral from soil
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Ground tissue system
It comprises of all tissues except epidermis and vascular bundles
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Cambium may or
may not be present
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Cambium
has the ability to form secondary tissues
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Closed vascular bundle: It lacks cambium between xylem and phloem
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Closed vascular
bundle is the characteristic feature of monocotyledonous stems
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Such types of vascular bundles are present in roots
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Such types of vascular bundles are found in stems and leaves
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The layer next to epidermis is cortex
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Endodermis is innermost layer of cortex, which bears the deposition of water impermeable
waxy material called suberin
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In the cells of pericycle, initiation of lateral roots and vascular cambium takes place during
secondary growth
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They possess 2-4 patches of xylem and phloem
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Dicot roots undergo secondary growth
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Pith is large and well-developed
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Xylem bundles are more than six i
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, polyarch
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Cortex is differentiated as outer hypodermis (having collenchymatous cells), middle cortical
layer, and inner endodermis
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Hence, the layer is also known as starch sheath
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Vascular bundle is conjoint, open, and with endarch protoxylem
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Monocotyledonous Stem

Vascular bundles are scattered
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It is conjoint and closed
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The abaxial (lower) epidermis bears more stomata than adaxial (upper) epidermis
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It carries out
photosynthesis
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Monocotyledonous leaf
It is also known as isobilateral leaf
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Both the surfaces of epidermis bear stomata
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