Some details about Parthenocarpy

Parthenocarpy

   

                    Have you ever tasted seedless grapes, guava and pomegranate which are so easily available in fruit markets nowadays? These fruits are produced by a phenomenon called parthenocarpy. Parthenocarpy means the development of fruits without pollination or any other stimulus. Noll ( 1902 ) first introduced this term. According to the present concept, it refers to the formation of fruit without fertilization ( Nitsch 1965 ).  

         Parthenocarpy is of widespread occurrence especially among plants which have larger number of ovules in each fruit e.g. pine apples, tomatoes, figs and melons.

         Parthenocarpy may occur as follows 1) fruit development without any pollination 2) fruit development stimulated by pollination 3) seedlessness as a result of the abortion of the embryos before the fruit reaches maturity.

            According to Nitsch (1965), there are three types of parthenocarpy namely

1. Genetical 

2. Environmental 

3. Chemically induced.

Genetical parthenocarpy

            This type of parthenocarpy is due to mutations or hybridization. An example for this could be seen in oranges which are developed through mutations in an axillary bud. This bud grew out into a branch bearing seedless oranges. Parthenocarpic cucumber is produced by hybridization. 

Environmental parthenocarpy 

            Parthenocarpy may result due to variation in environmental conditions such as frost, fog and low temperatures. Such environmental conditions interfere with normal functioning of sex organs leading to parthenocarpy. Heavy fog in the month of June caused the formation of seedless olives. If pear fruits are exposed to freezing temperatures for 3-19 hours, they grew into parthenocarpic fruits. Parthenocarpic chilly fruits are obtained by shifting the plants from temperatures of 32° -  38°C to 10° - 16°C at the time of dehiscence of anther. Parthenocarpy is induced in tomatoes with low temperatures and high light intensity. Under these conditions, pollination is poor.

Chemically induced parthenocarpy

              Plant hormones such as auxins and gibberellins in low concentrations have been very successfully employed to induce parthenocarpy in many plants which normally bear seeded fruits. These are applied in the form of paste or sprays. As a result of artificial pollination, most of the guava varieties developed into seeded fruits except an ' Allahabad Round' variety. In this variety, parthenocarpy could also be induced by treating the emasculated flowers with an aqueous extract of pollen. This "pollen hormone" effect could be duplicated by the application of indole acetic acid and indole butyric acids. Other plants where auxins could bring about parthenocarpic development of fruits include tomato, black berry, figs, cucurbits and citrus. Gibberellic acid has been reported to induce parthenocarpy in a number of rosaceous fruit trees, grapes, figs and tomato.

            It has been suggested that for the induction of parthenocarpy through auxin treatment, the growth substance should be applied sometime after anthesis (dehiscence of anthers) because an early application may damage the flowers and cause seed abortion and consequently fruit drop. On the contrary, gibberellic acid is applied preferably at anthesis.

            Parthenocarpy finds its importance in horticulture because seedless fruits are ideal for consumption either as such or in the juice and jam industries. Parthenocarpy may also increase proportion of edible part of the fruit.