Assignment 7

This image shows the stigma of the Brassica flower we dissected. The stigma is located on the tip of the carpel or multiple fused carpels. This is where the plant's pollen is germinated. The stigma is connected to the reproductive organs (male, female, or male and female).

Under the stigma in the middle (only partially visible) is the stamen. The stamen is the plant's male reproductive organs. In the stamen is the stalk, the filament, and the end of the stalk, the anthers. The stamen helps in fertilizing the plant's pollen. The plant's sperm cells are stored in the stamen.

Shown in the picture is the plant's carpel. The carpel is the plant's female reproductive organs. The ovaries are stored in the carpel. Carpels are sometimes also topped by a stigma. The pollen from other plants sticks onto the stigma. The function of this structure is to transport the unfertilized pollen to the ovary as well as make sure the pollen is compatible with the ovules. The ovary cannot be seen in this picture, but it is connected at the base of the style. This structure is responsible for the production and housing of the ovules, or eggs.

Here is a picture of an ovary in our flower's pistil. Once an ovary is fertilized by pollen it forms a zygote. This is because each egg and pollen grain is a haploid gamete. Once they meet they combine their haploid cells to create a diploid zygote. In many plants, the embryo created by this process of fertilization is surrounded by a fleshy structure that is the ovary itself. This is commonly known as fruit. Fruit acts as a method of transportation for a plant's embryo.

This an image of pollen at 100x. Pollen contains sperm cells which, on reaching another flower's stigma, travels down the style into the ovaries where they can fertilize the female gametes (egg cells). Only one sperm cell can fertilize an egg cell. Once the egg is fertilized it creates a barrier around itself to shut it off from another sperms cells to avoid double fertilization, which could result in excess chromosomes.