My wife’s breakfast of choice includes cold cereal and a banana. But unlike most mornings, my wife put on her “green tinted glasses” this particular morning and began to question her routine breakfast spread. Instead of seeing her average, mundane breakfast, she saw questions that needed answering. Why are bananas so readily available to her in the winter? Why are bananas shaped the way they are? Why don’t they have seeds? Why are they yellow? Why do they have a peel? Needless to say, I was thrilled when my beautiful and inquisitive wife turned to me for the answers and suggested I make it a blog post.
The bananas that we eat and can purchase at the grocery store even in the coldest of winters originate from tropical regions of our planet. There are many misconceptions that surround this unassuming fruit. The banana actually comes from herbaceous plants and not a tree. The banana is technically a berry. But my favorite misconception is that all bananas are the same. There are actually more varieties than the yellow crescent shaped ones we are used to. Some bananas are fuzzy, some are striped, and some even taste like strawberries.
The bananas we all know and love come from a single genus (or classification group larger than the species level) known as Musa. From this one genus, scientists have selectively bred and cultivated the perfect banana for eating. Scientists looked for bananas that had improved plant vigor, were hardier than other bananas, had a sweeter and more pleasant taste, and had a higher fruit to plant ratio. But my favorite trait that scientists looked for was parthenocarpy. This is a trait that causes bananas to have seed sterility… or in other words, the banana had no seeds! Once scientists found Musa bananas that possessed the desired traits, they bred them over and over again until they had created a delicious banana that is easy to eat and cultivate.
As you may have noticed (even without green tinted glasses) bananas start as a green color. Almost all plants have a green color due to a chemical called chlorophyll inside of them. Chlorophyll takes energy from sunlight and transforms it into nutrients that the plant needs. This chlorophyll inside a green banana is responsible for supplying the banana with nutrients. These nutrients make the fruit inside the banana sweet. Once the fruit behind the peel has reached a satisfactory level of nutrients, the banana starts to turn yellow in color. This happens because the fruit no longer needs chlorophyll to supply nutrients, so the chlorophyll breaks down causing the peel to become thinner and the fruit to become softer and edible. Ever try to eat a green banana? If you ever did, you might break a nail trying to peel it and your eating experience would be very dull and unsatisfying.
All fruit-bearing plants have various strategies at their disposal to help ensure their posterity survives. This usually involves a strategy to protect the seeds until they are fertile and then another strategy to distribute the fertile seed. Imagine, if you will, that you are an animal in the tropical jungle. Once the banana plant’s seeds are fertile, the flowers on the plant will produce a scent attracting you to the fruit. Once you encounter the fruit, its shape makes it easy to grab and pull off of the plant. You will find the peel has become yellow and soft, making it easy for you to peel and eat. You will take a bite and find the fruit delicious and filled with 30 to 150 black seeds. This is part of the banana plant’s brilliant design to disperse its fertile seeds once it passes through your system. Thankfully you are an animal so the seeds don’t bother you, but to humans that is a very undesirable trait. That is why scientists searched for seedless banana traits.
To start with a fruit that only grows in tropical jungles and is fairly undesirable as far as taste and seed number goes and create a seedless, scrumptious, easy to produce fruit is very significant in my book. Science once again has proven to be a very powerful tool for good. But there is a flip side to this miracle of biology. The bananas we eat are merely clones. Once scientists found the desired traits and selectively bred the bananas for many years, clones of these optimal bananas began to be produced. Now the banana you eat could be identical to the banana someone is eating in Rome. Since all the bananas we eat are clones, this means that one little disease that happens to affect our mass produced optimal banana could threaten to destroy the highly globalized fruit. In nature, there are checks and balances for this sort of thing. But when you biologically engineer something until all versions of that something have the same exact genes, it becomes a very fragile, all be it optimal, kind of something.
May you never look at your ordinary breakfast banana the same again.
If you read this whole blog post, you are my hero! Thanks for reading. Please feel free to leave me a comment and feedback below. Also, let me know if there is any particular science topic you would like me to look at “through green tinted glasses” and I will write about it.
Science Word of the Week: parthenocarpy–The development of unfertilized fruit which makes the fruit seedless.