METHODS OF FRUIT AND SEED DISPERSAL

Animal dispersal

Fleshy fruits are eaten by animals. Animals are attracted to the fruits by the bright colour, scent or the fact that it is edible. The seeds pass through the digestive tract undamaged and are passed out with faeces. E.g. tomatoes and guavas. Such seeds have hard, resistant seed coats.

Others have fruits with hooks or spines that stick on animal fur or on clothes. Later the seeds are brushed of or fall off on their own e.g. Bidens pilosa (Black jack).

Wind dispersal                                                               

Fruits and seeds are small and light in order to be carried by air currents. A fruit that is a capsule e.g. tobacco split or has pores at the top e.g. Mexican poppy. The capsule is attached to along stalk when swayed by wind the seeds are released and scattered.

Some seeds have hairy or feather-like structures which increase their surface area so that they can be blown off by the wind e.g. Sonchus. Others have wing-like structures e.g. Jacaranda and Nandi Flame. These extensions increase the surface area of fruits and seeds such that they are carried by the wind.

Water dispersal

Fruits like coconut have fibrous mescocarp which is spongy to trap air, the trapped air make the fruit light and buoyant to float on water. Plants like water lily produce seeds whose seed coats trap air bubbles.

The air bubbles make the seeds float on water and are carried away. The pericarp and seed coat are waterproof.

Self dispersal (explosive) Mechanism

• This is seen in pods like bean and pea.
• Pressure inside the pod forces it to open along lines of weakness throwing seeds away from parent plant.

See also

POLLINATION

SEXUAL REPRODUCTION IN PLANTS

ASEXUAL REPRODUCTION

REPRODUCTION IN PLANTS AND ANIMALS

BIOLOGY PRACTICAL ACTIVITIES