Imagine a tree assembled from smaller parts, like LEGOs.
Now let me blow your mind: living plant LEGOs already exist!
In nature, it’s called “inosculation”; when humans do it, it’s called “grafting”. Humans often graft a stem or bud from a desirable “scion” onto a hardier, older “rootstock”. Take a look at this crazy pic:
When the scion and rootstock grow together, you’ll have a Franken-plant that will have both sturdy roots and branches that bear delicious oranges!
You can’t graft just anything- plants have to be somewhat related for it to work- but the results are unbelievable.
When natural grafting, or inosculation, happens within one tree, it’s called autografting. Check out this insane pic of an old bicycle:
The tree is pretty much stuck with it now…
Inosculation can also occur between two different individuals. This pic of a “Husband and Wife” tree will blow your mind:
Notice how the trees aren’t just touching, they’re fully intersecting. Whoa!
Root grafting is even more common than branch grafting in the wild. Unfortunately, it’s hard to peek below ground. Here’s some #relatable aboveground content:
In terms of the items you have in your apartment, a lot of them might be the result of grafting too.
Your houseplants may be grafted. One really obvious example is when Hibiscus plants of multiple flower colors are grafted to a single rootstock.
You can also find the effects of grafting in your pantry. Citrus fruits, avocado, apples, and roses are all commonly grafted, among others.
So, now that you’ve seen grafting both done by humans and in the wild, get ready for your mind to be blown. Did you know people have made grafted art? Artists do some absolutely next-level stuff:
Axel Erlandson took it even further by opening a “Tree Circus” amusement park in Scotts Valley, CA in 1947 that was filled with grafted oddities:
Some of the trees were transported to the Gilroy Gardens amusement park and exist to this day:
Because grafting looks really awesome, and because we depend on it for food, you’d think that scientists would know how it works at a molecular level.
But that’s where things get weird.
We do know some things about the physiology of grafting. It uses many of the same processes as plant wound healing. First, a waxy substance seals off the open wound. Then plant cells start to divide and form an undifferentiated “callus”.
Because the two plants are pressed together, their callus interlocks and starts developing into vascular cambium, aka the stuff on the inside of plant stems. Eventually, the stem grows xylem and phloem, and the two grafted plants are connected as one functional plant.
What we’re still figuring out is how plants control this process, why certain plants are compatible and certain ones aren’t, and what effects grafting might have on whole plants.
Now, something you really won’t believe…
Grafted plants can share GENOMES.
Well, I hope you believed it, because it’s true.
And that means you can make NEW SPECIES by combining different genomes through grafting!
This is different from hybridization through sexual reproduction. In sexual reproduction, the two parents each pass down half of their chromosomes, so the offspring end up with the same number of chromosomes as the parents- so in many respects at least, they’ll be pretty similar.
Grafting, on the other hand, is asexual, and the offspring can get all of the chromosomes from both parents. That’s a lot of extra genetic information.
The offspring in this case look like a mix of the two grafted plants, but they’re bigger (probably due to the extra chromosomes making extra proteins).
The authors speculate that some common crop plants may have formed through grafting, and that new crop species can be produced using this method.
What will ~the future~ of grafting look like?
TBH, the future probably won’t look like that, but it’ll definitely hold more crazy grafting pics.
Sources & Further Reading:
Epstein, A.H. 1978. Root Graft Transmission of Tree Pathogens. Annual Review of Phytopathology 16: 181-192.
Fuentes, I., Stegemann, S., Golczyk, H., Karcher, D., Bock, R. 2014. Horizontal genome transfer as an asexual path to the formation of new species. Nature 511: 232-235. (Featured paper)
Mudge, Ken. The How, When, & Why of Grafting. Department of Horticulture, Cornell University. cornell.edu, 2017. Online course. https://courses.cit.cornell.edu/hort494/mg/history/HistGB.html
Reames, Richard. “Arborsculpture.” arborsculpture.blogspot.com, 2012.
Roose, Johnna. “May Bouquet: Hibiscus”. New Under the Sun Blog. https://newunderthesunblog.wordpress.com/2014/05/06/may-bouquet-hibiscus/ Photo credit for the grafted hibiscus to Monica Russell.
Smagala, Suzanne. “Tree Circus.” Ripley’s Believe it or Not, 2014. http://www.ripleys.com/weird-news/tree-circus/
Stegemann, S., Keuthe, M., Greiner, S., Bock, R. 2012. Horizontal transfer of chloroplast genomes between plant species. PNAS 109.7: 2434-2438.
Van Aken, Sam. “Tree of 40 Fruit: Trees.” samvanaken.com, 2017. https://www.samvanaken.com/trees/
Willey, Dan. “Grafting Orange Trees – How to Graft a Tree by T-budding.” FruitMentor, 2017. http://www.fruitmentor.com/grafting-orange-trees-t-bud
PLANT HUMOR 
Sam Van Aken’s little buddy looks like its taken root in the SciLi courtyard.
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Sam Van Aken’s little buddy looks like it’s taken root in the SciLi courtyard.
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And apostrophes are the callus of the linguistic world, but only when they are used correctly! Sorry about my poorly grafted first comment.
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