Campus notes on Natural History – The Wild Banana

A few years ago on a field trip to Singheshwar some teachers had brought back saplings of wild banana (Musa acuminata or Musa salaccensis) and had planted two of the three saplings on the side of the road leading from Jr. Auditorium to the Dining Hall (DH). The saplings survived but would not do much apart from leaving out a few leaf shafts in monsoon and drying up to inconspicuous stumps in the dry season.

This monsoon, one plant surprised many of us by growing plenty of leaf shafts and also a flower bud. The flowering started soon after and following are some observations on the pollination ecology of the plant.

The flower in bloom
The flower in bloom

I have been looking up on the jelly like secretion of the wild banana flower that has been blooming opposite the Senior Audi. The secretion was strange because I had never seen any flower do this with the only exception being the ferns that secrete a watery sweet fluid to attract ants that in turn keep the herbivores at bay.

I found that the jelly like secretion is a nectar concentrate of about 15-20 % sucrose (anyone who tastes it can verify this) and is primarily an adaptation based on its pollinator choice. Turns out that the wild banana prefers vertebrates (bats and birds) to invertebrates (insects) to help with pollination in it’s natural habitat (jungles of South East Asia). This behavior is termed as “Pollinator Syndrome” and “Zoophily” is the term given to vertebrate driven pollination.

The jelly secretion
Close-up of the flower: the jelly like secretion

I was not a little disappointed when I checked one morning, after assembly, to find that ants were on the nectar because one of the reasons to make the nectar viscous and sticky is to discourage insects. On closer examination I realised that only the last set of inflorescence (group flowering) was ant infested as the jelly had begun to dehydrate and ferment (tastes a little like Neera as Amresh put it). The fresh inflorescence and jelly secretion (happens overnight) was untouched by the ants! Nature had contrived to give evidence to confirm the need for the jelly, with a control right beside it and I almost dismissed it!

Bananas do not need pollination to develop fruits. In the absence of other plants nearby it seems they can self-pollinate and give seedless fruits (Parthenocarpy). This process is known as parthenogenesis. All we need to do is hope the fruits develop fully and then cut one open and see if the seeds have developed.

A few days ago I saw a hornet wasp on the banana plant at around 9:00 AM. I wonder if this contradicts the zoophily theory of pollination syndrome.

The jelly can keep out only the insects!
The jelly can keep out only the insects!

– Arun Kumar

References:

https://en.wikipedia.org/wiki/Zoophily

www.jstor.org/stable/2388300