Why do bananas easily break into thirds when squeezed?

[ilenisaatio]

Reminded by the recent thread “Why is the strawberry the way it is?”, I’ve been meaning to ask about bananas.

Some time ago, as I was breaking of bits of banana to our toddler by squeezing the fruit between two fingers, I noticed it kept breaking into almost neat thirds in cross-section. It has repeated every time I’ve done it, now that I’ve known to follow it. The tendency remains whether I use different amounts of fingers, or even something like BBQ-tongs (?) I’ve been wondering if the phenomenon originates already from the floral level.

So I ask if anyone knows why this happens?

[einsum]

Yes bananas flower’s ovary is tricarpellate, and although these carpels look fused in fruit development, they remain sufficiently structurally distinct within the final fruit.

So naturally these three weaker plane boundaries create preferential splits in banana - like how a wood splits along the grain.

Notice the image bottom left cross-section of ovary showing three carpels:

[ilenisaatio]

@einsum Thank you!