Today’s Wonder of the Day was inspired by Ashley from AL. Ashley Wonders, “How do seedless watermelons grow?” Thanks for WONDERing with us, Ashley!
On a hot summer day, there's nothing better than a nice tall glass of ice cold lemonade. Well, unless, of course, you pair that lemonade with a big wedge of juicy watermelon. The only drawback to enjoying the watermelon is the need to spit out the seeds constantly.
That minor annoyance can be avoided, however, if you purchase a special “seedless" variety of watermelon. If you take a gander around your local grocery store, you'll also likely find other seedless varieties of fruits, such as grapes.
If you think about it, are seedless fruits really fruits? As any botanist will tell you, the scientific definition of a fruit is a flowering plant's mature organ that contains seeds. If that organ doesn't contain seeds, can it really be considered a fruit?
Technically, a seedless fruit probably shouldn't be considered a fruit. However, since seedless fruits resemble their seeded counterparts in all other ways, everyone uses the term fruit for convenience. So how do we get these seedless fruits? Can you plant a seedless fruit?
The answer is no! You can't plant a seedless fruit, because the plants that produce them don't occur in nature because they're sterile. That means they can't reproduce. So how do we get seedless fruits? They have to be made.
Over the years, scientists have developed many different seedless varieties of fruits to make them more convenient to eat. Since they can't be planted, they have to be specially cultivated through different scientific processes.
For example, to make seedless grapes, new plants are made from existing plants. Adult grape plant stems are sliced diagonally and cut into sections. The cut ends are then dipped into a rooting hormone and planted. The new plants that begin to grow are basically genetic clones of the original parent plant, except that they produce seedless fruit.
Creating seedless grapes in this way dates back to the days of ancient Rome. That means that some seedless grape varieties might come from plants that are essentially over 2,000 years old, since they're clones!
In the case of seedless watermelons, the process of producing seedless fruits is completely different. Normal watermelon plants have two sets of chromosomes. Scientists discovered how to genetically engineer watermelon varieties that have four sets of chromosomes. If normal watermelon plants are pollinated with pollen from genetically-engineered plants, the resulting plants (called hybrids) have three sets of chromosomes, which makes them sterile and able to produce seedless watermelons.
One other method of creating seedless fruits that come from trees is known as grafting. In the grafting process, a branch from one tree is cut and attached to another fruit tree. This is usually done at a specific time of year when the sap in the trees is running high.
If the graft takes root on the new tree, it will begin to grow using the nutrients provided by the parent tree. Grafting allows a single tree to grow many different types of fruits, some of which can be special seedless varieties.
Scientists who study genetics are always looking to push the envelope when it comes to new varieties of seedless fruits. As technology advances, don't be surprised to see newer and better varieties of seedless fruits, such as tomatoes, cherries, cucumbers, and green peppers.