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Simply Scientific: Why does my clementine have seeds?

by Martin Payette February 11, 2020
Simply Scientific: Why does my clementine have seeds?

The first thing you do is grab two of them. Not three. If you grab three, then go ahead and take a fourth. You just don’t eat an odd number of clementines. 

Palpate it. Feel around its lumpy cool surface. Press a little with your fingers to confirm that the rind is only lightly gripping the fleshy walls of the pulp beneath. 

Mmm. Yes. That’s good.

For good measure, or maybe to prolong the anticipation, roll it around on the table under your palm. Gently. Every quarter inch of it.

Now, it’s almost time. Aim for the region around the pedicel, the slightly swollen part around where the stem was once attached.

Some will use their fingers for this part. This could leave a zesty residue under your nail. Maybe you like it that way, you silly bean.

But I prefer not to have sticky fingers. Call me dainty; I’ll plead guilty as charged. I use my teeth to break through the skin instead and taste that first spurt of citrus. 

Then, peel. One long strand. Some will make an orange-peel flower and that’s good too. 

Now you have it, that soft, bulbous, delicious fruit. Halve it with both hands. Pull a segment off. Put it in your mouth. Bite and feel the juicy…

SEED!? There’s a seed???

Disappointed? Understandable. The clementine’s seedlessness is one of its biggest draws, after all.

Why do some clementines have seeds and others don’t? The answer is simple. But first, a little history.

Brother Clément Rodier was a French missionary who helped run an orphanage in Algeria in the late 19th century. He introduced hundreds of fruit trees, ornamental trees and rose bushes to the orphanage’s land. He also enjoyed experimenting and developing hybrid plants and fruits. Hybrid plants or animals come from the naturally occurring or artificially induced sexual reproduction of two different breeds, species or genera.

Sometime around 1900, Rodier found a tree with fruit redder than a mandarin orange; not as sweet, but delicious nonetheless. It was the product of a mandarin flower having been cross-pollinated with a sweet orange (or just orange) tree. This new variety of mandarin orange was eventually called clementine in honour of Rodier.

Now, seedless fruits are a naturally-occurring mutation in many plants. It’s even been suggested that certain species have evolved in such a way that seedless fruits serve as decoys to distract herbivores from eating viable ones.

It’s certainly a trait desired by grocers and consumers, since the absence of seeds makes for a better eating experience, as well as a longer shelf-life.

Trees of seedless clementines are reproduced by grafting, which essentially involves sticking a clementine branch into any old stump. These seedless varieties come from being self-incompatible, which is sometimes a side-effect of being a hybrid (sort of like with a mule, which can’t reproduce). In this case, that means that the pollen from identical seedless clementine trees can’t physically reach all the way down to the ovary (plants have ovaries) at the bottom of the flower. The tree still produces fruit, but without pollination, it develops no seeds (sort of like chickens who lay sterile eggs when there’s not rooster around).

But that’s not the whole story, obviously. There is in fact at least one breed of clementine whose reproductive organs are self-compatible. And seedless clementine trees can be pollinated by this breed and by other varieties of orange, through a process called cross-pollinisation. All you need is a bee.

Growers cover their orchards with netting to keep the little buzzers off, but they can never be 100 per cent sure that a pollinator won’t somehow get through. And that means that sometimes, what was otherwise going to be a beautiful moment in your day, becomes a mildly disappointing one.

 

Graphic by @sundaeghost

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