Parthenocarpy ■ Natural and Induced
The term was coined by Noll in 1902. Fruits may sometimes develop without seeds. This may happen in several way:
(a) The flower is pollinated normally followed by fert i lization. However, after some time seed development ceases and the resulting fruit contains only aborted seeds. This condition is observed in certain variety of grapes.
(b) The flower is pollinated and the pollen germinates but fertilization fails and the germinating pollen grains can stimulate fruit growth without actual fertilization of the ovules.
(c) Inviable or even dead pollen may stimulate fruil formation.
(d) No pollination occurs at all as in the cultivated banana.
In all the instances mentioned above, the mature fruits are seedless. Seedlessness should not be confused with parthenocarpy. Parthenocarpy may be defined as the formation of fruits without fertilization. Parthenocarpy, as defined here, would not include the cases listed under the first case: (a) in which seed abortion occurs after fertili¬zation.
In other words, seedlessness and parthenocarpy are not synonymous, for two reasons.
(1) A seedless fruit may have developed after fertili zation by the subsequent collapse of the seeds.
(2) Parthenocarpic fruits may contain seed-like struc-tures. The mangosteen fruit is an example of such seeded parthenocarpic fruit with adventive embryos.
Nevertheless, the above definition of parthenocarpy includes atleast two different types, that is, parthenocarpy with or without the aid of pollen. These have been desig¬nated as stimulative and vegetative parthenocarpy. The examples noted above under (b) and (c) fall under stimu¬lative and vegetative parthenocarpy. The examples noted above under (b) and (c) fall under stimulative parthenocarpy whereas (d) comes under vegetative parthenocarpy.
In the year 1963, Nitsch has classified parthenocarpy into three types which are explained below:
1. Genetical Parthenocarpy: In a number of plants, specially which are cultivated for their edible fruits, one hay find both seeded and parthenocarpic varieties. This ;ype of parthejiocarpy is known to arise through mutation or lybridization. The famous novel oranges arose from a lormal seeded Citrus variety through mutations in an auxiliary bud which grew out into a branch bearing seedless oranges. Besides this it also occurs in Citrus, Cucumis,^ Musa, Vitis, etc.
Environmental Parthenocarpy:
Low temperature, heavy fog, frost, and severe winter appear to induce parthenocarpy in olive, pear, tomato, tobacco, cucumber, Capsicum etc. Especially the night ;emperature in the range of 10-16°C, and a short day of eight lours are known to be the most favourable conditions for parthenocarpic induction. Campbell observed that a heavy fog in June caused the formation of seedless olives and Hostermann noted the formation of seedless pears after a frost. Parthenocarpic fruits in pears were obtained by Lewis (1942) by exposing flowers to freezing temperatures. Osborne and Went were able to be induce parthenocarpy in ;omatoes with low and high light intensity.
