Expert: Dana Krempels, Ph.D. - 1/2/2008

Question
Hello,
What purpose does the banana fruit serve for the tree if it's not the holder of the seed? I guess this question applies to all plant life forms whose fruits are seedless.
Thanks!

Answer
Dear Matt,

Wild type bananas actually *do* have seeds.  It's only the cultivars we eat that completely lack them, and they probably would not last long in the wild without human help.

On the other hand, they do grow like mad (vegetatively), and the ones I have in my backyard grow like gangbusters despite producing fruit regularly.  It could be that the parthenogenic fruit are just not enough of a liability to select against seedless individuals, since they grow via runners so well.  

Seedless fruit occur in nature periodically due to random mutations, but unless the plant that produces them is an aggressive vegetative grower, a seedless plant isn't going to stay in the gene pool.  Only when humans discover them and cultivate them do they stick around, to our mutual benefit.

There are some plant species, however, that produce *some* seedless fruit in the same crop as fruit with seeds.  In this case, it's believed that the seedless fruit serve to decoy herbivores and make them fill up on seedless fruit, allowing more of the seeded ones to survive.  So the genetic tendency for seedlessness--at least in some offspring--can actually be adaptive.

Hope that helps.

Dana