The reproductive life of plants: Flowers and Fruits

Just as animals do, plants also have a sex life! Their reproduction, however, involves a two-phased cycle. In less evolved plants as found in the Bryophyte and Pteridophyte divisions, these two successive phases produce individuals quite independent from one another.

In more evolved vascular plants, not only are individuals of one of the reproductive phases much smaller in size, they spend their short life span entirely dependent and physically attached to the individuals of the other reproductive phase. These plants are the seed-bearing specimens belonging to the Spermatophyte division. This division contains all the flowering plants which are called Angiosperms . The flowers of these plants contain the male and female reproductive organs.

As we all know, flowers are very different in shape, size, color and odor. Even their fertilization process varies. Some species have female and male flowers on different plants (Aspen and Willow trees) while other species have different male and female flowers growing on the same plant (Pine and Oak trees). However, most species have hermaphrodite flowers, meaning that both male and female reproductive cells are found in the same flower.

Although we usually admire a flower for its beauty or fragrance, little do we realize that it is also a very clever and efficient reproductive device. A flower is composed of three parts. Strangely, the part we often find to be the most pretty is sterile. Composed of petals and sepals, this part is called the perianth and generally surrounds the two fertile parts of the flower. The female organ or pistil is most commonly found in the center of the flower and includes the ovary, the style and the stigma. The male organ or androecium usually surrounds the pistil and liberates pollen from its stamens.

When fertilization occurs in the pistil, the flower begins its gestation period. Although the petals may wither and drop off, the ovary, which contains a fertilized seed, will transform itself into a fruit. Fruits vary enormously; some are fleshy like the cherry while others are like the samara of the Maple tree. Still, some are dehiscent or open up to shed their seeds like the Poplar tree capsules and still others hide their seeds inside their fruit such as the apple or pear.

If you would like to see seeds germinate, you can easily do so at home with dry beans. Take a wide-mouth, low glass jar, insert a few sheets of wet paper towels, place a few beans on them and cover them up with another wet paper towel. Put the jar in a warm, dark place, always keeping the paper toweling moist. Check the germination process every day and soon you will see the first leaves or cotyledons sprout and the delicate root system develop. Check to see if beans are monocotyledons or dicotyledons. You can also note your observations in a logbook, just like researchers do. Don't forget to indicate the date you started your experiment, as well as the date on which all changes occurred. Then you can try the same experiment with other seeds and compare the results. Later, when the leaf and root systems are more developed, plant the seeds in earth and watch them grow into bean plants!