Gabe15

That is mostly true Jeffery, except that in bananas parthenocarpy and ploidy level are unrelated, and parthenocarpy can be present in diploid, triploid and tetraploid varieties. Sterility in bananas come form other, non-ploidy related meiotic errors and mechanisms such as pollen tube growth inhibition. There are extremely sterile parthenocarpic diploids, as well as extremely fertile parthenocarpic triploids. Nearly every combination and degree of ploidy level, sterility (of both gamete types, male and female) and parthenocarpy is present in at least some varieties. Many banana varieties, even triploids, can in fact set seed if pollinated. This is why banana breeding is possible.

One way to think about it is this: the growth of fruit is normally triggered by the fertilization and growth of seeds within the fruit. If a banana were to be completely sterile due to triploidy or any other source of female sterility, and thus could not form seeds, then how is the fruit still able to swell and develop? The answer is vegetative parthenocarpy, in which the hormone release promoting the fruit to develop that would normally be associated with the growth of seeds is replaced and executed by an autonomous action. Parthenocarpy is completely separate from anything else, and it even occurs in wild populations of banana, which is how they were first domesticated.

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Growing bananas in Colorado, Washington, Hawaii since 2004. Commercial banana farmer, 200+ varieties.