Sexual Reproduction in Plants
Perhaps you may not find this as interesting as the previous but it is important too. Plants don’t bother with mating or walking around looking for a mate[i]. Plants that reproduce sexually use a process called pollination. Pollen is a tiny dust like particle that is moved from one plant to another to fertilise it. Pollen is made in a part of the plant called the anther and glands on the ends of the stigma. There are two main ways pollen can be transported: by insects and by wind. Insect pollinated flowers have brightly coloured petals and a sweet substance called nectar which attracts the insects. When the insect -i.e. a bee- goes to get the nectar (which it wants), its body brushes against the anthers and pollen sticks to their body. The insect then goes onto another plant and deposits the pollen from the last plant into the stigma of the current plant.
Wind pollination is simply pollen being blown from one plant to another. The stigmas and anthers of these planets tend to hang outside of the plant so that pollen can be blown and catched easily. The two different types of pollinated flowers have many differences, and these can be represented in a table:
Once the pollen has landed on the stigma it grows what is known as a pollen tube to transport it to the ovary to fertilise the ovule (like an egg in a mammal). Once the ovule is fertilised it develops into a seed. The plant then has to disperse its seeds. There are several ways that a plant can use to disperse its seeds: · Wind – seeds are blown away from the plant · Animal (internal) – seeds are eaten by animals and pooped out[ii] · Animal (external) – seeds get caught on animal’s coats and dropped later It is very important that the seeds are far away from the original plants to avoid competition between the parents and the off-springs for water, space, food and sunlight. [ii] For example, tomato plants have been noted to grow at sewage works. |
