BOTANY Higher Secondary Second Year - Textbooks Online

2.2. Anatomy of monocot and dicot roots
The embryo develops into an adult plant with roots, stem and leaves
due to the activity of the apical meristem.. A mature plant has three kinds
of tissue systems - the dermal, the fundamental and the vascular system.
The dermal system includes the epidermis, which is the primary
outer protective covering of the plant body. The periderm is another
protective tissue that supplants the epidermis in the roots and stems that
undergo secondary growth. The fundamental tissue system includes
tissues that form the ground substance of the plant in which other permanent
tissues are found embedded. Parenchyma, collenchyma and sclerenchyma
are the main ground tissues. The vascular system contains the two
conducting tissues, the phloem and xylem. In different parts of the plants,
the various tissues are distributed in characteristic patterns. This is best
understood by studying their internal structure by cutting sections (transverse
or longitudinal or both) of the part to be studied.
Primary structure of monocotyledonous root - Maize root
The internal structure of the monocot roots shows the following tissue
systems from the periphery to the centre. They are epiblema or
rhizodermis, cortex and stele.
Rhizodermis or epiblema
It is the outermost layer of the root. It consists of a single row of
thin-walled parenchymatous cells without any intercellular space. Stomata
and cuticle are absent in the rhizodermis. Root hairs that are found in the
rhizodermis are always unicellular. They absorb water and mineral salts
from the soil. Root hairs are generally short lived. The main function of
rhizodermis is protection of the inner tissues.
Cortex
The cortex is homogenous. i.e. the cortex is made up of only one
type of tissue called parenchyma. It consists of many layers of thin-walled
parenchyma cells with lot of intercellular spaces. The function of cortical
cells is storage. Cortical cells are generally oval or rounded in shape.
Chloroplasts are absent in the cortical cells, but they store starch. The
cells are living and possess leucoplasts. The inner most layer of the cortex
is endodermis. It is composed of single layer of barrel shaped
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