Question

D. LONG ANSWER TYPE
1. Name the different types of androecium found in
flowers
2. Name the type of androecium found in
(a) China rose (b) Bombax
​

Answer 1

1) :-

The androecium is the third set of floral organs composed of stamens or micro- sporophylls.

Ordinarily, each stamen is composed of a slender stalk-like filament sup­porting a knob-like spore case or the anther .

Stamen showing parts

Each anther consists of two lobes (anther lobes) connected by a connective which can be clearly seen on the dorsal side as an extension of the filament. Each anther lobe, again, has two pollen sacs or pollen chambers placed longitudinally. There are longitudinal grooves or sutures along the ventral face of the anther demarcating the pollen chambers. Each pollen chamber re­presents a microsporangiur and contains innumerable microspores or pollens.

The stamen, therefore, is a microsporophyll bearing four microsporangia. While this is the normal case, there are some flowers where the anther possesses only two pollen chambers (i.e., bisporangiate) and in Malvaceae even these two pollen chambers fuse developing a mature unilocular anther.

A flower may some­times be reduced to a single stamen as seen in the cyathium inflorescence .

Filament:

In rare cases a stamen may be devoid of a filament or sessile as seen in the stamens of Arum maculatum . On the other ex­treme, a stamen may not develop any fertile anther when it is sterile and termed a staminode as seen in Cassia and Canna .

In the latter case it is also petaloid. The showy labellum of Scitaminae is formed of staminodes. In water-lily the filament is flat showing its transition from petals .

Sessile stamen of Arun maculatum, FLower of Canna Indica and Flower of Hedychium

The filament may be white or coloured yellow, blue, black, etc., like petals. While the filament is ordinarily simple, in Ricinus communis it is found to be branched. When filaments are very long, stamens protrude out of the flower and are term­ed exserted. On the contrary, when stamens remain within the flower; they are termed inserted.

Filaments sometimes bear appendages. Most characteristic of these is the staminal which is horny in Calotropis and cup-shaped in Eucharis , Pancratium and some other flowers of Amaryllidaceae.

Branched stamen of castor, Staminal corona in calocropis procera flower and Staminal corona in Eucharis amazonica

Connective:

Ordinarily, the connective is a patch of tissues connecting the two parallel anther lobes .It is a prolongation of the filament and contains the conducting strands.

The connective, however, may be (1) extremely small or altogether wanting as in some species of Euphorbia and in Adhatoda zeylanica (Acanthaceae) where the anther lobes are very close together. This condition is termed discrete.

(2) In the lime tree (Tilia ) and in fusticia gendarussa (Acanthaceae) the connective is called divaricate as it develops in such a way that the two anther lobes are separated from one another.

(3) In Salvia (Labiatae) a pet liar condition called distractile is noticed where the connective is a long stalk-like body placed crosswise on the filament sepa­rating the two anther lobes.

One anther lobe is fertile while the other is abortive, usually represented merely by a deltoid plate.

The connective also may bear appen­dages when it is called appendiculate. The connective is prolonged into a feathery appendix beyond the sagittate anther of the oleander (Nerium odorum ) and some other flowers of Apocynaceae. These appendices in Nerium unite to form a staminal corona .

Connective

Anther:

All Angiospermous anthers are bilobed and quadrilocular (i.e., formed of four micro- sporangia) at an early stage of development and this condition is seen in most mature stamens.

Rarely, however, the anther becomes unilocular or one-chambered either by the abortion of one lobe and destruction of the portion wall between the two chambers or the destruction of the entire partition tissue separating the four chambers.

This condition is seen in the family Malvaceae . The grooved ventral side of an anther usually faces the gynoecium or the centre of the flower and this condition is known as introrse; but, in a few cases as in Gloriosa superba, Iris, Colchicum, etc., the anther faces the petals when the condition is called extrorse.

Anthers may be linear (Acalypha ), rounded (Mercurialis ), sagittate (Vinca ), sinuous (peculiar -shaped appearance as seen in the cucur­bits ), reniform (china-rose ), etc. The anther also may be appendi­culate like the connective as may be seen in Erica cinerea of Ericaceae .

Anther

Attachment of the Anther to the Filament:

The mode of attachment of the anther to the filament varies . (1) It is adnate when the filament or its continuation, the connective, appears to be attached throughout the whole length of the back of the anther as seen in magnolia and water-lily.