Anatomy of Flowering Plants Flashcards
3 types of tissue system
These are the epidermal tissue system, the ground or
fundamental tissue system and the vascular or conducting tissue system.
where is epidermis found,
The epidermal tissue system forms the outer-most covering of the whole
plant body and comprises epidermal cells, stomata and the epidermal
appendages – the trichomes and hairs. The epidermis is the outermost
layer of the primary plant body
what kind of cells are present in epidermis
It is made up of elongated, compactly arranged cells, which form a continuous layer. Epidermis is usually singlelayered. Epidermal cells are parenchymatous with a small amount of
cytoplasm lining the cell wall and a large vacuole.
what is the cuticle
The outside of the
epidermis is often covered with a waxy thick layer called the cuticle which
prevents the loss of water. Cuticle is absent in roots.
explain leaf epidermis
Stomata are structures
present in the epidermis of leaves. Stomata regulate the process of
transpiration and gaseous exchange. Each stoma is composed of two beanshaped cells known as guard cells which enclose stomatal pore. In
grasses, the guard cells are dumb-bell shaped. The outer walls of guard
cells (away from the stomatal pore) are thin and the inner walls (towards
the stomatal pore) are highly thickened. The guard cells possess chloroplasts
and regulate the opening and closing of stomata. Sometimes, a few epidermal
cells, in the vicinity of the guard cells become specialised in their shape and
size and are known as subsidiary cells. The stomatal aperture, guard
cells and the surrounding subsidiary cells are together called stomatal
apparatus.
when water enters gaurd cells, they open(turgud). when water exitsgaurd cells, closed(flacccid)
what are epidermal appendages
The cells of epidermis bear a number of hairs. The root hairs are
unicellular elongations of the epidermal cells and help absorb water and
minerals from the soil by increasing surface area of root. On the stem the epidermal hairs are called
trichomes. The trichomes in the shoot system are usually multicellular.
They may be branched or unbranched and soft or stiff. They may even
be secretory. The trichomes help in preventing water loss due to
transpiration.
what is the ground tissue system
All tissues except epidermis and vascular bundles constitute the ground
tissue. It consists of simple tissues such as parenchyma, collenchyma
and sclerenchyma. Parenchymatous cells are usually present in cortex,
pericycle, pith and medullary rays, in the primary stems and roots. In
leaves, the ground tissue consists of thin-walled chloroplast containing
cells and is called mesophyll.
how is the arrangment of vascular bundles in dicots and monocots
The vascular system consists of complex tissues,
the phloem and the xylem.The xylem and
phloem together constitute vascular bundles
(Figure 6.2). In dicotyledonous stems,
cambium is present between phloem and
xylem. Such vascular bundles because of the
presence of cambium possess the ability to form
secondary xylem and phloem tissues, and hence
are called open vascular bundles. In the
monocotyledons, the vascular bundles have no
cambium present in them. Hence, since they do
not form secondary tissues they are referred to
as closed.
In dicots, the presence of cambium makes it possible for the plant to undergo secondary growth ie woody growth
what are two types of arragnement of xylem and phloem in plants
When xylem and phloem within a
vascular bundle are arranged in an alternate
manner along the different radii, the
arrangement is called radial such as in roots.
In conjoint type of vascular bundles, the xylem
and phloem are jointly situated along the same
radius of vascular bundles. Such vascular
bundles are common in stems and leaves. The
conjoint vascular bundles usually have the
phloem located only on the outer side of xylem
outermost layer of dicot root
The outermost layer is epidermis. Many of
the epidermal cells protrude in the form of
unicellular root hairs. The cortex consists of
several layers of thin-walled parenchyma cells filled with interceullular spaces
explain the inner part of root ie the stele
The innermost layer
of the cortex is called endodermis. It
comprises a single layer of barrel-shaped cells
without any intercellular spaces. The
tangential as well as radial walls of the
endodermal cells have a deposition of waterimpermeable, waxy material-suberin-in the
form of casparian strips. Next to endodermis
lies a few layers of thick-walled
parenchyomatous cells referred to as
pericycle. Initiation of lateral roots and
vascular cambium during the secondary
growth takes place in these cells. The pith is
small or inconspicuous. The parenchymatous
cells which lie between the xylem and the
phloem are called conjuctive tissue. There
are usually two to four xylem and phloem
patches(tetrach condition). Later, a cambium ring develops
between the xylem and phloem. All tissues
on the innerside of the endodermis such as
pericycle, vascular bundles and pith
constitute the stele.
what is the arrangement of xylem in root
There is a radial arranegement of xylem and phloem in the root.
The xylem has small sized components called protoxylem aligned toward periphery. It also has larger components called metaxylem which are located towards the centre.
This arrangement of metaxylem and proxylem is called exarch condition. ( exarch- )
what is the anatomy of monocot root
The anatomy of the monocot root is similar to
the dicot root in many respects (Figure 6.6 b).
It has epidermis, cortex, endodermis,
pericycle, vascular bundles and pith. As
compared to the dicot root which have fewer
xylem bundles, there are usually more than
six (polyarch) xylem bundles in the monocot
root. Pith is large and well developed.
Monocotyledonous roots do not undergo any
secondary growth.
