Sinking your teeth into a juicy, ripe watermelon is one of summer’s greatest pleasures, especially when you don’t have to spit out any seeds. In fact, humans have made many fruits seedless for a more pleasant eating experience.
But without seeds, how do such plants reproduce?
Fertilization in fruit plants is usually a two-part process: the pollen of a male plant fertilizes the ovule of a female plant; This ovule becomes a seed, while the ovule becomes a fruit. However, some plants have both male and female reproductive systems, allowing self-fertilization. Without fertilization, no seed or fruit can grow.
In rare cases, however, it is possible for a fruit to develop without fertilization, and this occurs through a few different methods, collectively known as parthenocarpy, after the Greek words for „virgin fruit.” Charles KeserA professor emeritus at the University of California, Davis, who has spent his career studying the molecular evolution of plant ovules, told Live Science that while parthenocarpy is widely used in modern agriculture, it began as a natural phenomenon.
Navel oranges, for example, came about after a random genetic mutation long ago produced a branch with seedless fruit. (Many point out A tree in a Brazilian monastery 1800s.) People grafted cuttings of the branch onto other trees, and today, all navel oranges in the world are clones of this original. Because these clones do not perform well at self-pollination, an orchard of identical plants produces most of its fruit through parthenocarpy. A similar discovery led to Seedless grapesIt is believed to have originated in ancient Rome making their way to America through Iran and Turkey in the 1870s.
Related: Why are bananas berries, but strawberries are not?
For watermelons and bananas, it’s an even more complicated process. Plants often have more than two copies of each chromosome — a condition known as polyploidy — and seedless fruits develop when crossovers produce offspring with incompatible chromosomes. Commercial growers, for example, cross a watermelon plant with four chromosomes with a watermelon plant with two copies of the chromosomes to create seedless watermelons. Progeny ending up with an odd number of chromosomes are seedless, while offspring with an even number are used to produce more seeds. Similarly, all business Bananas Today there are three copies of chromosomes, so they are only transmitted asexually.
In some cases, botanists have learned how to induce polyploidy or parthenocarpy by using hormones. Pineapple Diploid, but they can produce fruit without fertilization when treated with the hormone gibberellic acid.
Gasser said scientists have a few hypotheses as to why plants might have developed these abilities. For one thing, plants can hybridize more easily than vertebrates, and hybridization opens up new evolutionary potential. Although some combinations do not pan out, researchers have documented examples of „”.Mixed virility,” in which a hybrid is more fit than its parent. Polyploidy creates larger seeds to hold all those extra chromosomes, making them more likely to survive the acidic environment of an animal’s stomach.
Finally, because the purpose of fruiting is to attract animals to disperse their seeds, parthenocarpy may eventually allow trees to produce more fruit at a lower energetic cost if they do not need to produce seeds. „One can imagine parthenocarpy arising, even though not all fruits have seeds, because it continues to attract vectors that move the seeds,” Gasser said.
Regardless of why seedless fruits exist, they represent an interesting thought experiment Stacey Smith, a plant evolutionary biologist at the University of Colorado Boulder. On the one hand, many evolutionary bottlenecks cannot sustain themselves without human intervention. But they are largely successful for the same reason. Wild navel oranges are scarce, but California is estimated to produce 76 million of them are cartons Only this year.
„My personal opinion is that all domesticated plants have succeeded in one way or another because they don’t have to make much of themselves. We do that for them,” Smith told LiveScience. „Since they reproduce sexually and don’t make seeds, who cares? We’ll never stop eating watermelons, and if we can make seedless ones it means we eat more watermelons.”
„Oddany rozwiązywacz problemów. Przyjazny hipsterom praktykant bekonu. Miłośnik kawy. Nieuleczalny introwertyk. Student.