Ovule: The ovule is a component of the female reproductive system of seed plants. It is where female reproductive parts are produced and maintained. Ovules are housed in ovaries at the base of the carpel, which includes an aperture at the top, stigma, and a neck called a style. After fertilisation, these cells eventually develop into a seed, which subsequently ripens to form a full-grown adult plant. Ovule is also known as the megasporangium in flowering plants.

After fertilisation, the ovule develops, and its wall begins to thicken to transform into a seed. In contrast, the ovary begins to grow around it and develop into the fruit. Remember that certain plants, such as the avocado, only have a single ovule in their ovary, whilst other plants, such as the kiwifruit, have numerous ovules, which eventually mature into multiple seeds in the fruit.

Types of Ovules

There are six types of ovules in a plant, and these types of ovules are based on their shapes. 

• Orthotropous or Atropous: The area where the nucellus and integuments merge is known as chalaza. The Orthotropous is where the body of the plant ovule is straight so that the chalaza, the funicle (this attaches the ovule of the plant to the placenta), and the micropyle aligns. 

• Anatropous: A scar that marks the area where the seed was eventually attached to the fruit by the funicle is called the hilum. In Anatropous, the ovules are completely inverted throughout development so that the micropyle lies close to the hilum. 

• Hemi-Anatropous: Here, the ovules take the shape of a right angle about the funicle. Its shape eventually looks like the ovule is lying on its side.

• Campylotropous: The shape of the Campylotropous ovule is bent, and the alignment that occurs between the chalaza and the micropyle ceases to exist; therefore, the embryo sac becomes slightly curved.

• Amphitropous: The body of the Amphitropous ovule is so curved that the ovule and the embryo sac takes the shape of a horseshoe.

• Circinotropous: The shape of circinotropous is the most distinct of them all. The funicle in the case of the circinotropous ovule is so long that it creates a full circle around the ovule and its micropyle ultimately points upwards. It is deemed to be the most distinctly shaped out of the six types of ovules.

Functions of Ovule

• It plays an important role in the process of sexual reproduction. Once a pollen grain falls on the stigma of a flower of its similar species.
• In addition, it sends out a pollen tube below through the style. Then this tube enters inside the ovary and then reaches into the ovule of the plant.
• Once that occurs, the fertilization process can arise as the nucleus of the pollen grain is brought down of the tube for merging with the nucleus in the embryo sac.
• Notably, the male alternative of it is generally pollen. It contains the male gametophytes.

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By Team Learning Mantras