Types of Parthenocarpy
Three types of Parthenocarpy are generally recognized:
- Genetical
- Environmental,
- Chemically-induced.
Genetical Parthenocarpy is observed in many species cultivated for their fruit. It arises due to mutations or hybridization. Generally parthenocarpic varieties have sterile pollen so that the pollination stimulus is available, but fertilization does not take place. As a result, a fruit is produced which has no seeds. The famous navel orange has arisen from a normal seeded Citrus variety through mutation in an axillary bud, which formed a branch bearing seedless fruits. Several cultivated varieties of grapes and cucumber have also resulted from bud mutations.
Environmental Parthenocarpy is the result of some environmental conditions such as frost or low temperature which interferes with the normal reproductive process. In tomato, for instance, cultivation under low temperature and high light intensity can induce Parthenocarpy. Under these conditions pollination is so poor that seeds are not produced but ovary is activated to form the fruit Induced Parthenocarpy involves treatment of the flowers with certain plant growth regulators. Auxins and gibberellins at low concentrations have been successfully utilized for induction of parthenocarpy in a large number of plants which otherwise bear seeded fruits. Seedless guava, tomato, and straw- fruits have been obtained by this method. Parthenocarpy is important in horticulture because seedless fruits are more convenient to consume and are particularly suitable for the industry manufacturing jams, jellies and fruit juices. Gibberellins also cause fruit enlargement (in grapes which are considered commercially beneficial for packaging and marketing, and also cause looseness of bunches).