FAMILY OF THE WEEK: POLYGONACEAE

Antigonon leptopus


Polygonum auriculata


Polygonum auriculata

FAMILY OF THE WEEK: POLYGONACEAE

In India the family is represented by 8 genera and 110 species occurring chiefly in Himalayas.

Vegetative characters:

Mostly herbs but few are shrubby or trees. Sometimes they are climbers such as Antigonon which climb with the help of tendrils terminating the racemes.

The stems are often with swollen nodes and in Cocoloba platyclada the stems and branches are flattened to form phylloclades. The epidermis often forms red pigment. The leaves are alternate, rarely opposite or whorled, simple and entire, toothed or lobed as in Rheum. The leaves are stipulate and the stipules are characteristic of the family. They are usually membranous and forming a complete sheath(ochrea) around the stem above the leaf base. Crystals of Calcium oxalate are often present in the epidermal cells.

Inflorescence and flowers:

The inflorescence is primarily a compound raceme whose branches are cymose. The flowers are small, bracteates, hermaphrodite, actinomorphic, cyclic or acyclic and hypogynous.

The calyx is of three to six, free or basally connate, often petalloid, white or red and persistent sepals which are often enlarged and membranous in fruit. The aestivation is imbricate. The petals are absent. The androecium is of 5-9 stamens. The filaments are free or united at the base. The anthers are dithecous and opening lengthwise.

An annular nectar secreting glandular disc is mostly present at the base of the ovary. Gynoecium is usually tricarpellary and syncarpous. The ovary is superior and unilocular. The style is two-four clefted. The stigmas are various.

Fruits and seeds:

The fruit is an angled achene usually enclosed in the calyx. The seeds have copious endosperm.

Pollination and seed dispersal:

The flowers are pollinated by wind or insects. The fruits are mostly distributed by wind as the persistent calyx forms a membranous wing. Sometimes they have wings which help distribution by birds or animals.

Examples:

Fagopyrum esculentum (Buckwheat,Kuttu)

Fagopyrum tataricum (Duckwheat)

Oxyria digyna

Rheum (Rhubarb)

Rumex acetosa (Garden sorrel)

Rumex acetosella (Sheep sorrel)

Polygonum (Knot weed)

Antigonon leptopus (Coral vine)