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, special mechanism has evolved to produce seed and fruit. For example: Asteraceae. What are the different type of special mechanisms? What is meant by apomixis and parthenocarpy? What is parthenocarpy?

Apomixis

Fruit and Seed Formation Without Fertilization

Fruit and Seed Formation Without Fertilization

 

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 Leeuwenhook. 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 single ovule. Example: Citrus
  2. False polyembryony – More than one embryo develops from different ovule. 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 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 the productivity. But, parthenocarpy process is expensive. As a result, hybrid seeds and fruits become too expensive.

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Practise This Question

The winged seeds, such as those produced by Maple are dispersed by the wind.