Re: Responding to your answer about no seeds in bananas.

Hello Dan,

Bananas are parthenocarpic, which, translated to English, means that they
are capable of reproduction without being pollinated, which will result in
a seedless fruit.  Many fruits are parthenocarpic.  However, bananas are
quite often pollinated in breeding programs, and many varieties are seeded
varieties.  I don't know who told you that the seeds are sterile, but I
assure you, they are not.  They are quite viable and WILL germinate, and
most likely result in another seeded variety.  I'm not going to get into a
discussion of diploids and triploids within this answer, but I strongly
recommend that you get ahold of a book called BANANAS, by William Lessard,
and another called FRUITS OF WARM CLIMATES, by Julia Morton
I also suggest that you contact Don Chafin at Going Bananas Nursery in
Homestead Florida at (305) 247-0397.  With those sources, you will have
all of the most expert knowledge available regarding bananas.

There are dozens of fruits that are either parthenocarpic or produce
aborted seeds. When this outcome is entirely natural, then you are correct
in your statement that the actual fruit production is of no benefit to
the plant itself.  Without Man's intervention and propagation by asexual
means, then the original plant would live its life and that would be the
end of it.  But asexual propagation (grafting, air layering, division,
rooting of cuttings, etc.) is most often commenced by discovery of the
plant in the first place, and intentional propagation.  For example, only
three weeks ago we discovered a navel orange tree which sported one
variegated branch.  As soon as it has good buds, we intend to try to
propagate it and try to get it to hold the variegated characeristic.  Why
did the plant do this?  Nobody knows, but for genetic alterations to occur
spontaneously in nature is nothing uncommon at all.  Now it will be 
propagated simply by the sheer chance of us happening to notice it.  Your
guess is as good as anybody's as to how many plants in this world have
had similar occurrences, went undiscovered, and wound up dying out.
In short, there is no benefit in particular to the plant, but I'm sure
glad it happens.

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Admin note 

David Hershey adds the following:

Actually, seedless fruits could be an advantage to a plant species. For
example, in seasons when pollination or fruit set is prevented due lack of
pollinating insects or bad weather, seedless fruits could help prevent
animals that disperse the plant's fruits and seeds from migrating or
dying.  In pineapple (Ananas comosus), the top of the seedless fruit can
root and form another plant so even a seedless pineapple fruit can
function in reproduction. In wild parsnip (Pastinaca sativa), seedless
fruit are preferentially eaten over seeded fruit by an herbivore (Zangerl
et al., 1991).

In many species, seedless fruit production occurs only under certain
circumstances or to a certain extent so the plants can also produce seeded
fruit. Even if an ability for seedless fruit production under certain
circumstances offers no advantage to a plant species, it may persist
during evolution if it is not a particular disadvantage. Traits that offer
no advantage or disadvantage would not be selected for nor selected
against so could persist simply by chance. Plants that can only produce
seedless fruit, such as triploid bananas, could even survive by natural
vegetative reproduction if the triploid condition gave the plant an
advantage over its diploid relatives.


Reference:

Zangerl, A.R., Berenbaum, M.R. and Nitao, J.K. 1991. Parthenocarpic fruits
in wild parsnip: Decoy defense against a specialist herbivore. Evolutionary
Ecology 5:136-145.