Sexual Reproduction in Plants

The Seed  The seed is the product of sexual reproduction in most plants.  The seed contains an embryo, a food supply and a seed coat that keeps it from drying out.  Seed-bearing plants can be classified into two groups based on seed structure.  The two groups are called Angiosperms and Gymnosperms.

Angiosperms  Angiosperms are flowering plants  The seeds form inside the flower  When mature the seeds are enclosed in a case.

Sexual Reproduction in Angiosperms  The flowers produced by angiosperms contain the plant’s reproductive organs  The female reproductive organs are called the pistil  The male reproductive organs are called the stamen

Pollination  In order for the seeds to develop, pollen grains from the anthers must reach the stigma of the pistil.  This process is called pollination

 There are two types of pollination used by angiosperms;  Self-pollination - the males and female gametes come from the same plant  Cross –pollination – the male and female gametes come from two different plants. The two most common agents of cross- pollination are wind and insects.

Fertilization  The pollen grain must grow a pollen tube to reach the ovule  When the pollen reaches the ovule a zygote and a cotyledon are formed.  The cotyledon contains stored food.

Gymnosperms  Gymnosperms do not produce flowers  Produce seeds inside the cones  Seeds have a coat that protects them but are not inside a case

Sexual Reproduction in Gymnosperms  Gymnosperms produce their seeds inside cones. For this reason they are called conifers.  In some species male and female cones are produced on separate trees.  In most conifers male and female cones are produced by each tree.

Pollination and Fertilization  Pollination proceeds the same as in angiosperms  Fertilization also requires the formation of a pollen tube to allow the pollen to reach the egg.

Plants without seeds  Plants such as mosses and ferns reproduce through spores  Like gametes spores are haploid however, a spore can develop into a new plant without fertilization.

 The mature form called a sporophyte will release the spores  Under the correct conditions the spore will develop into a gametophyte.  The two main advantages for dispersal are; that they are light and that they can survive unfavourable conditions by staying dormant until the conditions are ideal.