Fruit and Seed Formation Without Fertilization

Fruits and seeds are not only essential  in the life cycle of flowering plants; they are also utilized as sources of food. In a few species, a special mechanism has evolved to produce seed and fruit. This mechanism can prominently be seen in Asteraceae.  Read on to explore these special mechanisms.

Apomixis

Apomixis is a type of asexual reproduction that mimics sexual reproduction to produce seeds in flowering plants. Two types of apomixis are found in flowering plants. These are as follows:

1. An unfertilized diploid egg developing into the embryo through parthenogenesis. Example: Rosaceae
2. Embryo arising directly from the nucellar cells of the ovule. Example: Citrus

Polyembryony

Polyembryony may be defined as the phenomenon of more than one embryo developing from a single ovule. It was discovered by Leeuwenhoek. Polyembryony occurs commonly in many animals and plants, Example: Nine-banded armadillo. Polyembryony is classified into two types. These are as follows:

1. True polyembryony – More than one embryo develops from a single ovule. Example: Citrus
2. False polyembryony – More than one embryo develops from different ovules. Example: Mango

Parthenocarpy

Parthenocarpy may be defined as the production of fruit from an unfertilized egg. It can be achieved by naturally or artificially. Example: seedless watermelon.

Two types of parthenocarpy are found. These are as follows:

1. Stimulative parthenocarpy – In this process, pollination is required to produce fruits. Example: Seedless watermelons.
2. Vegetative parthenocarpy – In this process, pollination is not required to produce fruits. Example: Seedless cucumbers.

Hybrid cultivation of fruits by parthenocarpy is used to increase productivity. But, parthenocarpy process is expensive. As a result, hybrid seeds and fruits become quite expensive.

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