Hemitropous Ovule in Angiosperm

An ovule is the reproductive structure of a flower that develops into a seed after fertilization. The ovule contains the female gamete, which is fertilized by the male gamete to form a zygote. The orientation of the ovule in the flower is of great significance and is used to classify the ovules into different types.

Hemitropous ovule is one of the types of ovules found in angiosperms. The term "hemitropous" is derived from the Greek words "hemi" meaning half and "tropos" meaning turn. Thus, hemitropous ovules are half-turned ovules and are horizontally oriented.

Characteristics of Hemitropous Ovule

- A hemitropous ovule is curved and bent, with the micropyle (the opening through which the pollen tube enters) and the chalaza (the base of the ovule where the integuments are attached) almost parallel to each other.
- The ovule is attached to the placenta by a short stalk called the funicle.
- The integuments (outer layer) of the ovule are fused together except at the micropyle, which is open.
- The embryo sac (the female gametophyte) is located at the micropylar end of the ovule.
- The pollen tube enters the ovule through the micropyle and fertilizes the egg cell and the central cell to form the zygote and endosperm, respectively.

Significance of Hemitropous Ovule

Hemitropous ovules are significant in angiosperms due to the following reasons:

- The curved shape of the ovule allows for efficient pollination as the pollen tube can easily navigate through the ovule to reach the embryo sac.
- The micropyle is located at the top of the ovule, which prevents the entry of unwanted pollen grains and ensures the fertilization of only the desired pollen grain.
- The fusion of the integuments except at the micropyle provides protection to the developing embryo and endosperm.

Conclusion

Hemitropous ovules are horizontally oriented ovules found in angiosperms. They are curved and bent, with the micropyle and chalaza almost parallel to each other. The ovule is attached to the placenta by a short stalk called the funicle. The curved shape of the ovule allows for efficient pollination, and the micropyle is located at the top of the ovule, which prevents the entry of unwanted pollen grains. The fusion of the integuments except at the micropyle provides protection to the developing embryo and endosperm.