Page 17 - LN-ANATOMY OF FLOWERING PLANT

Endodermis It lies just beneath the general cortex in the form of single layer of
barrel-shaped cells surrounding the stele. It is the innermost layer of cortex. In
sunflower, it contains starch, v hence is called starch sheath.
3. Pericycle
It exists between the endodermis and the vascular bundles. The cells are
sclerenchymatous with lignified cell walls and a few parenchymatous cells dispersed
in between. Each patch is associated with phloem of the vascular bundle and is
called the hard bast.
4. Vascular Strand
The vascular strand consists of many vascular bundles, arranged in the form of a
ring around a central pith and inner to pericycle.
Each vascular bundle consists of phloem (on the outside), xylem (towards the Inner
side) with a strip of cambium, between the two.
The vascular bundles are thus, conjoint (i.e., consists of both xylem and phloem),
collateral (i.e., phloem and xylem are on the same radius) and open (i.e., a strip of
cambium present between the two).
5. Medullary or Pith Rays
These are non-vascular areas present in between the vascular bundles. The
medullary rays connect pith with pericycle and cortex. Cells are larger than those of
cortex. The medullary rays take part in radial conduction of materials, i.e., food,
water, gases, etc.
6. Pith or Medulla
It consists of the central part of the stem. It consists of rounded, oval or polygonal
parenchymatous cells. Intercellular spaces are absent. The cells store food materials
and waste products.
Features for Identification of Dicotyledonous Stem
Dicotyledonous stem can be easily identified with the following features
(i) Occurrence of multicellular hair over epidermis.
(ii) Collenchymatous hypodermis.
(iii) Presence of bundle caps or sclerenchymatous pericycle over vascular bundles.
(iv) Endarch xylem.
lyionocqtyledonous Stem
The monocot stem possesses only primary structure. The different monocot stem
from outside towards inside are consists of epidermis, hypodermis, ground tissue
and vascular system.
1. Epidermis
It is single layered, having stomata in it. The cells have a thick cuticle layer on the
outside.