Ovule

Definition

An ovule is a reproductive structure found in seed plants, specifically within the ovary of a flower, that contains the female gamete or egg cell. It is crucial in the process of fertilization and seed development, as it develops into a seed upon successful fertilization by pollen. The ovule consists of a protective integument, a nucellus, and the embryo sac, which houses the egg cell, making it integral to the reproductive cycle of angiosperms.

5 Must Know Facts For Your Next Test

1. Ovules are typically found within the ovary of a flower, which is part of the female reproductive structure known as the pistil.
2. Each ovule has a structure called a micropyle, an opening that allows pollen to enter for fertilization.
3. After fertilization, the ovule develops into a seed, while the surrounding ovary matures into fruit that aids in seed dispersal.
4. Angiosperms often have multiple ovules within each ovary, leading to the potential for producing many seeds from a single flower.
5. The process of double fertilization occurs in angiosperms where one sperm fertilizes the egg cell and another fuses with two polar nuclei to form triploid tissue, which becomes endosperm for nourishing the developing embryo.

Review Questions

• How does the structure of an ovule facilitate its role in reproduction?
  • The structure of an ovule is specifically designed to protect and nurture the female gamete during reproduction. The integument surrounds the ovule providing protection from environmental factors and potential threats. The presence of the micropyle allows pollen to easily enter and fertilize the egg cell housed within the embryo sac. This intricate design ensures that once fertilization occurs, the ovule can efficiently develop into a seed, highlighting its essential role in plant reproduction.
• Discuss how the process of double fertilization is significant in angiosperms regarding ovules.
  • Double fertilization is significant in angiosperms because it leads to the formation of both an embryo and endosperm from a single fertilization event involving an ovule. One sperm fertilizes the egg cell, forming a diploid zygote that develops into the embryo. The second sperm fuses with two polar nuclei to form triploid endosperm, which provides nutrition for the developing embryo as it grows within the seed. This dual process enhances reproductive efficiency and ensures better survival chances for seedlings.
• Evaluate the evolutionary advantages conferred by ovules in seed plants compared to non-seed plants.
  • Ovules provide significant evolutionary advantages to seed plants over non-seed plants by offering greater protection and nourishment to developing embryos. In seed plants, ovules allow for internal fertilization and development, reducing reliance on water for reproduction as seen in non-seed plants like mosses and ferns. The seeds that arise from ovules can be dispersed over long distances via various mechanisms such as wind or animals, increasing colonization potential. Additionally, seeds can remain dormant during unfavorable conditions, enhancing survival rates compared to non-seed plant spores that are more vulnerable to environmental changes.

Related terms

Pollen: A fine powder produced by the male structures of flowering plants, containing male gametes that can fertilize the ovule.

Fertilization: The process where the male gamete from pollen unites with the female gamete in the ovule, leading to the formation of a zygote.

Seed: A mature ovule that has undergone fertilization, containing an embryo and a supply of nutrients, encased within a protective seed coat.