Morphology in Flowering Plants Flashcards
what are the parts of a plant
The angiosperms show large diversity
in external structure or morphology.
The angiosperms are characterized by
presence of roots, stems, leaves,
flowers and fruits.
The underground part of flowering
plant is the root system while the
portion above the ground forms
shoot system.
what is the primary root? what are lateral roots and secondary and tertiary roots?
In majority of the dicotyledonous plants, the direct elongation of the radicle
leads to the formation of primary root which grows inside the soil.
It bears lateral roots of several orders that are referred to as secondary,
tertiary, etc. roots.
what are tap roots
The primary roots and its branches constitute the tap root system, as seen in the mustard
plant. It is common in dicotyledonous plants
what are fibrous roots
In monocotyledonous
plants, the primary root is short lived and
is replaced by a large number of roots.
These roots originate from the base of the
stem and constitute the fibrous root
system, as seen in the wheat plant
what are adventitious roots
In some plants, like grass,
Monstera and the banyan tree, roots arise
from parts of the plant other than the
radicle and are called adventitious roots
what are functions of root
The main functions of the
root system are absorption of water and
minerals from the soil, providing a proper
anchorage to the plant parts, storing
reserve food material and synthesis of
plant growth regulators.
what are the regions of the rooot system
The root is covered at the apex by a thimble-like
structure called the root cap (Figure 5.3). It
protects the tender apex of the root as it makes
its way through the soil. A few millimetres above
the root cap is the region of meristematic
activity. The cells of this region are very small,
thin-walled and with dense protoplasm. They
divide repeatedly. The cells proximal to this
region undergo rapid elongation and
enlargement and are responsible for the growth
of the root in length. This region is called the
region of elongation. The cells of the elongation
zone gradually differentiate and mature. Hence,
this zone, proximal to region of elongation, is
called the region of maturation. From this
region some of the epidermal cells form very fine
and delicate, thread-like structures called root
hairs. These root hairs absorb water and
minerals from the soil.
what is the stem
The stem is the
ascending part of the axis bearing branches, leaves, flowers and fruits. It
develops from the plumule of the embryo of a germinating seed.
The stem bears buds, which may be terminal or axillary. Stem is generally
green when young and later often become woody and dark brown.
what are the parts of the stem
The stem
bears nodes and internodes. The region of the stem where leaves are
born are called nodes while internodes are the portions between two nodes.
what is the function of stem
The main function of the stem is spreading out branches bearing
leaves, flowers and fruits. It conducts water, minerals and photosynthates.
Some stems perform the function of storage of food, support, protection
and of vegetative propagation.
what is the leaf
The leaf is a lateral, generally flattened structure borne on the stem. It
develops at the node and bears a bud in its axil. The axillary bud later
develops into a branch. Leaves originate from shoot apical meristems and
are arranged in an acropetal order. They are the most important vegetative
organs for photosynthesis.
parts of the leaf
A typical leaf consists of three main parts: leaf base, petiole and lamina
(Figure 5.7 a). The leaf is attached to the stem by the leaf base and may bear two lateral small leaf like structures called
stipules. In monocotyledons, the leaf base expands
into a sheath covering the stem partially or wholly.
In some leguminous plants the leafbase may
become swollen, which is called the pulvinus.
(ii)The
petiole help hold the blade to light. Long thin flexible
petioles allow leaf blades to flutter in wind, thereby
cooling the leaf and bringing fresh air to leaf surface.
(ii)The lamina or the leaf blade is the green expanded
part of the leaf with veins and veinlets. There is,
usually, a middle prominent vein, which is known
as the midrib. Veins provide rigidity to the leaf blade
and act as channels of transport for water, minerals
and food materials.
what are the types of venation of leaf
The arrangement of veins and the veinlets in the
lamina of leaf is termed as venation. When the
veinlets form a network, the venation is termed as
reticulate (Figure 5.7 b). When the veins run
parallel to each other within a lamina, the venation
is termed as parallel (Figure 5.7 c). Leaves of
dicotyledonous plants generally possess reticulate
venation, while parallel venation is the characteristic
of most monocotyledons.
what are the two types of leaves
A leaf is said to be simple, when its lamina is entire
or when incised, the incisions do not touch the
midrib. When the incisions of the lamina reach up
to the midrib breaking it into a number of leaflets,
the leaf is called compound. A bud is present
in the axil of petiole in both simple and compound
leaves, but not in the axil of leaflets of the compound
leaf.
what are two types of compound leaves
The compound leaves may be of two types
(Figure 5.8). In a pinnately compound leaf a
number of leaflets are present on a common axis,
the rachis, which represents the midrib of the leaf
as in neem.
In palmately compound leaves, the
leaflets are attached at a common point, i.e.,
at the tip of petiole, as in silk cotton.
