The Open Door Web Site
Part XIX : Colonizing and Populating Habitats :
Asexual Reproduction : Introduction
A strawberry plant
Daffodils, Bristol, UK
The water hyacinth
COLONIZING AND POPULATING HABITATS
Asexual reproduction in Plants : Vegetative Reproduction
It is amongst the plants that we find the most sophisticated methods of asexual reproduction. Strawberries and spider plants produce runners over the ground, irises and ferns produce rhizomes underground, daffodils and hyacinths produce daughter bulbs and potatoes produce daughter tubers.
In this way a single daffodil which is planted in a garden will produce a cluster of daffodil plants after a few years. These plants are not able to disperse themselves; seeds produced by sexual reproduction are better for dispersal. Asexual reproduction is very useful for colonizing a piece of land where there are other species of plants growing.
Quite often the daughter plants remain attached to the mother plant so that the colony or clone of plants produced by asexual reproduction are all interconnected. It is difficult to know whether all the daughter plants should be called individuals or whether they are just parts of a single super plant.
Hyacinth bulb with daughter bulbs growing from it
The daughter plants can, however, survive on their own once they have grown roots. Gardeners will usually separate plants that have grown in this way to give them more space to grow.
The Water Hyacinth
Asexual reproduction is a very good way of reproducing large numbers of offspring rapidly. For land plants, however, it is not a very good way of dispersing the offspring. Amongst aquatic plants, however, this is not true. The daughter plants can break away and float down a river to establish a new colony far away from the parent. This the case for the water hyacinth.
The water hyacinth came originally from the Amazon basin in South America. Today it is a serious pest in North America, tropical Africa and South East Asia. This plant was accidentally introduced by men to these regions and it grew rapidly in the rivers and lakes. In certain parts of tropical Africa, transport by river boat has become impossible because this weed has completely blocked whole river systems.
Floating mats of the water hyacinth can be up to two metres thick and 14 kilometres long. In one growing season 25 water hyacinth plants can reproduce asexually and grow to cover 10000 square metres (1 hectare). This is about the size of a football pitch and it contains approximately two million plants which altogether mass as big as a fully loaded jumbo jet!
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