Plants have to reproduce in order to avoid extinction. There are two main steps in plant reproduction: Pollination and Fertilization. In order to reproduce, plants have flowers, the sex organ of any plant. In order to understand how plants reproduce, we need to understand the structure of a flower.
Structure of a Flower
Flowers have four basic parts:
- The sepal, which protects the flower bud,
- The petals.
- The stamen, the name given to several of the male parts of a flower. The stamen produces pollen, which contains the sperm, the main sex cell of a plant;
- The stigma, the female part which has a long tube called a style leading down to the ovary.
Pollination occurs when either the wind or insects like bees move the pollen from stamen to the stigma of another flower. The bee moves between flowers as it collects the nectar (the liquid produced in a flower's nectary) that the flowers make. The bees take the nectar and some pollen back to their hive, while the pollen from one flower that was taken to the other flower lands on that flower's stigma.
Fertilization occurs when an egg cell (in the ovary) and a pollen cell meet. When the pollen lands on the stigma, the pollen produces a pollen tube that goes down the style and into the ovary, bringing the sperm cell with it. When the pollen tube reaches the egg cell, the sperm cell in the pollen tube meets with the egg cell. The egg cell has been fertilized and seeds of the plant are formed.