Seedless oranges grow through a process called vegetative propagation, primarily grafting and sometimes budding, because they cannot reproduce sexually due to their lack of seeds. This method relies on cloning a desirable seedless variety.
Here's a breakdown:
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Origin of Seedless Varieties: The seedless navel orange, a popular variety, originated from a single mutated orange tree discovered in Brazil in the 1870s. Since the fruit was seedless, it couldn't reproduce through seeds.
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Grafting: The primary method of propagation involves grafting a scion (a cutting from the seedless navel orange tree) onto the rootstock of another citrus tree (which does produce seeds, but these seeds will not grow into the desired navel orange).
- Rootstock Benefits: The rootstock provides the grafted seedless orange tree with disease resistance, vigor, and other desirable traits.
- Scion's Role: The scion determines the type of fruit the tree will produce – in this case, seedless navel oranges.
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Budding: A variation of grafting, budding involves inserting a single bud from the seedless variety into the rootstock. The process is similar to grafting in that it clones the desired fruit.
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The Cloning Process: Because grafting and budding involve taking living tissue from the original seedless tree, every seedless navel orange tree is essentially a clone of the original Brazilian tree.
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Why No Seeds? The lack of seeds in navel oranges is due to a genetic mutation that affects the development of the ovules (which become seeds when fertilized). The flowers are still pollinated, but the ovules don't develop into viable seeds.
In essence, seedless oranges don't "grow" from seeds. Instead, they are propagated through cloning techniques to maintain the desired seedless trait of the original mutated tree. The initial seedless variety was discovered organically, but since then, humans have helped the spread of the seedless varieties.
