Discuss different aspects of seed dispersal.
Answers
Seed dispersal is carried by three mediums...
1) Through water
2) Through wind
3) Through animal or human bodies
Seeds can be dispersed in four ways:
1. Wind dispersal: dandelions have fruits with parachutes of hairs that catch the wind and are blown about. Sycamore fruits have wings which can be blown about and carried over distances.
2. Water dispersal: fruits which float, such as those of the water lily and the coconut palm are carried by water. Coconuts can travel for thousands of kilometres across seas and oceans. The original coconut palms on South Sea islands grew from fruits which were carried there from the mainland by ocean currents. Mangroves in swamp regions in countries such as Thailand are another example.
3. Animal dispersal: seeds of juicy fruits are carried by birds and other animals. The fruits are eaten, but only the juicy parts are digested. The stones and pips leave the animal's body via the droppings which may be some distance away from the parent plants. e.g. blackberry, cherry and apple. In the case of mistletoe, the sticky fruits are eaten by birds which then clean their beaks on the bark of trees, leaving behind a sticky seed which can grow into a new mistletoe plant on the tree. (Mistletoe is a plant parasite). Small seeds can be carried on the feet of birds and other animals. Fruits with hooks and barbs, e.g. the burdock fruit are carried in the hair, fur and wool of animals. Squirrels bury nuts, including acorns, for food supplies over the winter, but sometimes leave some behind which may grow into new plants in the spring.
4. Explosions: some plants disperse their own seeds. The pods dry and split open suddenly with some considerable force which throws their seeds for some distance. e.g. laburnum, broom, peas.
It would not do for seeds to fall and grow beneath their parent plants because of increased competition for food, light, water etc. Hence why seeds are dispersed.