Morphology in Flowering Plants 2 Flashcards
a flower is a modified shoot. justify
A flower is a modified shoot wherein the shoot
apical meristem changes to floral meristem.
Internodes do not elongate and the axis gets
condensed. The apex produces different
kinds of floral appendages laterally at
successive nodes instead of leaves. When a
shoot tip transforms into a flower, it is always
solitary
what is infloresence
The arrangement of flowers on the floral axis is termed as inflorescence. Depending
on whether the apex gets converted into a flower or
continues to grow, two major types of inflorescences
are defined – racemose and cymose. In racemose
type of inflorescences the main axis continues to
grow, the flowers are borne laterally in an acropetal
succession(pea,wheat) (Figure 5.11).
In cymose type of inflorescence the main axis
terminates in a flower, hence is limited in growth.The
flowers are borne in a basipetal order (petunia,chili)(Figure 5.12).
what is the flower
The flower is the reproductive unit in the
angiosperms. It is meant for sexual reproduction.
what are the 4 whorls of the flower
A typical flower has four different kinds of whorls
arranged successively on the swollen end of the
stalk or pedicel, called thalamus or receptacle.
These are calyx, corolla, androecium and
gynoecium. Calyx and corolla are accessory organs,
while androecium and gynoecium are reproductive
organs. In some flowers like lily, the calyx and
corolla are not distinct and are termed as perianth.
types of flower based on precense of gynoecium and androciuem
When a flower has both androecium and
gynoecium, it is bisexual. A flower having either
only stamens or only carpels is unisexual.
types of flower based on symmetry
In symmetry, the flower may be
actinomorphic (radial symmetry) or
zygomorphic (bilateral symmetry). When a flower
can be divided into two equal radial halves in any
radial plane passing through the centre, it is said
to be actinomorphic, e.g., mustard, datura, chilli.
When it can be divided into two similar halves only
in one particular vertical plane, it is zygomorphic,
e.g., pea, gulmohur, bean, Cassia. A flower is
asymmetric (irregular) if it cannot be divided into
two similar halves by any vertical plane passing
through the centre, as in canna.
types of flower based on no of floral appendages
A flower may be trimerous, tetramerous or
pentamerous when the floral appendages are in
multiple of 3, 4 or 5, respectively.
types fo flower based on presence of bract
Flowers
with bracts-reduced leaf found at the base of the
pedicel - are called bracteate and those without
bracts, ebracteate.
types of flower based on position of calyx, corolla and androecium wrt ovary
In the hypogynous(hypo=below,gynous-ovary) flower the
gynoecium occupies the highest position while the other parts are situated
below it. The ovary in such flowers is said to be superior, e.g., mustard,
china rose and brinjal.
If gynoecium is situated in the centre and other
parts of the flower are located on the rim of the thalamus almost at the
same level, it is called perigynous. The ovary here is said to be half
inferior, e.g., plum, rose, peach.
In epigynous(epi-above, gynous- ovary) flowers, the margin of
thalamus grows upward enclosing the ovary completely and getting fused
with it, the other parts of flower arise above the ovary. Hence, the ovary is
said to be inferior as in flowers of guava and cucumber, and the ray
florets of sunflower.
what si the calyx
The calyx is the outermost whorl of the flower and the members are called
sepals. Generally, sepals are green, leaf like and protect the flower in the
bud stage. The calyx may be gamosepalous (sepals united) or
polysepalous (sepals free).
what is the corolla
Corolla is composed of petals. Petals are usually brightly coloured to
attract insects for pollination. Like calyx, corolla may be also united gamopetalous (petals united) or polypetalous (petals free). The shape
and colour of corolla vary greatly in plants. Corolla may be tubular, bellshaped, funnel-shaped or wheel-shaped.
what is aestivation
The mode of arrangement of sepals or petals in floral bud
with respect to the other members of the same whorl is known as
aestivation.
The main types of aestivation are valvate, twisted, imbricate
and vexillary
different types of aestivation
When sepals or petals in a whorl just touch
one another at the margin, without overlapping, as in Calotropis, it is
said to be valvate.
If one margin of the appendage overlaps that of the
next one and so on in a specified direction as in china rose, lady’s finger and cotton, it is called twisted.
If the margins of sepals or petals overlap one another but not in
any particular direction as in Cassia and gulmohur, the aestivation is
called imbricate.
In pea and bean flowers, there are five petals, the largest
(standard) overlaps the two lateral petals (wings) which in turn overlap
the two smallest anterior petals (keel); this type of aestivation is known
as vexillary or papilionaceous.
