Page 11 - LN-ANATOMY OF FLOWERING PLANT

region. The cortex helps in performing vital functions, such as storage, etc.
iii. Endodermis This is the innermost layer of the cortex. It is single-layered, barrel-
shaped and arranged without intercellular spaces. The cells are parenchymatous.
The presence of bands of suberin on the radial and transverse wall is the
characteristic feature. These bands are called casparian strips. The endodermal
cells of roots usually have thick, radial and inner tangential walls.
These thick-walled cells form a continuous ring which is interrupted at certain places
by passage cells, which are thin-walled and usually present opposite to the
protoxylem region.
A well-developed endodermis is present in all types of roots, aerial stems of woody
dicotyledons and gymnosperms with characteristic casparian thickenings.
The endodermis helps to control the movement of water and air between the cortex
and xylem. It also helps to maintain the root pressure and conducts water to the
protoxylem.
iv. Pericycle It is made up of a single layer or many layers of cells present between
endodermis and vascular tissue. In roots, pericycle comprises cells of parenchyma.
The pericycle is absent in roots and stems of some aquatic plants.
v. Medullary Rays The-medullary rays are non-vascular areas which occur between
vascular bundles in dicot stems for lateral conduction. These are made up of
parenchyma cells. These originate from the apical meristem. They serve the function
of lateral transport.
vi. Pith The central portion of root and stem is occupied by pith. It contains
parenchymatous cells and also sclerenchymatous cells laticifers, medullary vascular
bundles, in some cases. In leaves, the ground tissue is parenchymatous and
possesses chloroplast.
It performs the function of photosynthesis. The main function of pith is storage of
water and food materials.
vii. Ground Tissue of Leaves In leaves the ground tissue of petiole is made up of
parenchymatous cells with distinct intercellular spaces. In the lamina, the bulk of
ground tissue is called mesophyll, which is usually differentiated into palisade and
spongy parenchyma.
These cells are thin-walled and possess chloroplasts. The main function of
mesophyll is in photosynthesis.
3. Vascular Tissue System
A vascular bundle is a strand of conducting tissue, which is generally composed of
xylem and phloem in monocots and xylem, phloem and cambium in dicots.

These tissues originate from the procambium and apical meristems. The