Biology Today - February 2018

The free stamens are called polyandrous. They may be equal or unequal in length. The two common

types of unequal stamens are tetradynamous (four long and two short, H.J., %UDVVLFD) and

didynamous (two long and two short, H.J., 2FLPXP).

Diplostemonous

Stamens of outer whorl

alternate with petals

(alternipetalous) and stamens

of inner whorl lie opposite to

the petals (antipetalous), HJ

0XUUD\DH[RWLFD&DVVLD.

Obdiplostemonous

Here, stamens of outer whorl

lie opposite to the petals

(antipetalous) whereas those

of inner whorl alternate with

petals (alternipetalous), HJ

'LDQWKXV, 6WHOODULD

Depending

upon the

position of

stamens

Fixation of anthers

• The mode of attachment of the anther to the filament varies greatly in flowers.

Dorsifixed

The filament is fixed to

the dorsal side or back

of the anther and

anther is immovable,

H.J., +LELVFXVURVD

VLQHQVLV, 3DVVLIORUD,

6HVEDQLD, etc.

Versatile

The filament is

attached to the

middle of the

connective so that

anther lobes can

swing on it freely,

H.J., grasses.

Basifixed

The filament

is attached to

the base of

the anther, as

in mustard,

'DWXUD,

radish.

Adnate

The filament is fixed

to the anther in such

a manner that it runs

up the entire length

of the anther at its

backside, H.J., 0DJQROLD

5DQXQFXOXV1\PSKDHD.

Types of fixation of anthers

Types of connective

• Connective can be of following types:

(i) Discrete : The connective is very narrow, so that the two anther lobes lie in
close proximity as in $GKDWRGD, (XSKRUELD sp.

(ii) Divaricate : The connective is broad and the two anther lobes are separated
as in 7LOLD sp.

(iii) Distractile : In 6DOYLD, the connective is highly elongated. Its one end
bears a fertile anther lobe while the other end has a sterile anther lobe.
(iv) Appendiculate : The connective becomes feathery and grows beyond the
anther.

Dehiscence of Anthers

Transverse

Slits appear breadthwise,

HJ0DOYD$OWKDHD

Valvular

Wall of anther lobes breaks at places and gets

lifted like valves, H.J., barberry, camphor.

Porous

Dehiscence is by pores, which appear at the

tips (6RODQXP tomato) or at base (&DVVLD).

Irregular

Anther wall breaks

irregularly, H.J.,

1DMDV

Laterorse

Slits appear on

the sides.

Extrorse

Slits lie towards the

outer side of petals.

Introrse

Slits are formed towards the inner

side or centre of the flower.

Types of

dehiscence of anthers

Longitudinal

Slits appear lengthwise, HJ

'DWXUDmustard5DQXQFXOXV

&LWUXV

GYNOECIUM

• It is the fourth whorl made up of one or more carpels (megaspo-
  rophylls). Depending on the number of carpels, gynoecium may be
  monocarpellary, bicarpellary, tricarpellary, tetracarpellary, pentacar-
  pellary and multicarpellary having one, two, three, four, five and
  many carpels, respectively.

Apocarpous

Gynoecium comprises of free carpels, H.J.,

5DQXQFXOXV.

Syncarpous

Gynoecium comprises of two or more carpels

which are fused, H.J., +LELVFXV.

Cohesion of carpels