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I’m not gonna lie – I was kinda dreading writing this article.
Well, not writing it – researching it. Tissue culture seemed a bit dull, but it turns out that not only is it more interesting than I assumed, but also more pervasive in everyday life than one might think.
It also starts with quite a sad story.
The fundamentals of tissue culture were discovered by Gottlieb Haberlandt, an Austrian botanist (his son came up with the idea for the birth control pill, and his dad brought soy to Europe). Unfortunately, due to the limitations of nineteenth-century lab equipment, he could only theorise as to how tissue culture could work.
His theory was that of totipotency – the idea that you can grow an entire plant from one (or a few) cells. He knew how to do it, but couldn’t grow his cells explants into full plants due to the limitations if his lab.
What is plant tissue culture?
Plant tissue culture is the practice of taking plant cells and using them to create entire plants. Haberlandt’s theory was true – any living cell, whether differentiated or undifferentiated, can form other cell types or even an entire plant.
Why is plant tissue culture so useful?
There are LOADS of applications of plant tissue culture that affect our everyday life.
1 – Micropropagation
This is the one the house plant world is most familiar with. A TONNE of popular house plants are created using tissue culture.
The one with the most press is probably the Monstera Thai Constellation, which is a variegated Monstera that has speckly variegation and doesn’t revert. They made a Thai constellation by manipulating the cells of a Monstera deliciosa, and used the tissue from that plant to create millions of clones.
If you think about it, that’s intense. Taking a relatively rare (at the time – Thais were made in 90s) plant and then making MILLIONS of clones from that one plant…incredible.
2 – Disease reduction
Orchids are affected by tonnes of viruses, including the dreaded Cymbidium mosaic virus. Tissue culture allowed botanists to create virus-free orchids. The tissue-cultured orchids were 100% virus free, whereas 83% of the non-tissue-cultured ones had the virus.
The samples were randomly selected from Nepal. The studies linked above, and is actually…kinda interesting.
3 – Conservation
Plant poaching is MASSIVE industry, especially, unfortunately, due to the exponential growth of the house plant industry. Aglaonema Pictum tricolor is one of the plants that was tissue-cultured in an attempt to stop it from dying out. Unfortunately, the current methods aren’t quite yielding comparable results. Still, it’s a popular plant, I’m sure they’ll get it done eventually.
4 – Mass produce metabolites
This is something I’d actually never considered, but makes sense.
Metabolites are compounds that, in this case, plants produce as an intermediate or end result of metabolism.
Humans use a LOT of metabolites – medications, spices, and supplements.
Not only can we use tissue culture to rapidly reproduce, for example, chilli plants, but we can also use tissue culture to make a plant that produces exactly the flavour of chilli that we want (and then make millions of them).
5 – Manipulate crop seasonality
When plants grow naturally, we need to wait for them to do things such as set seed. With tissue culture, we can produce plantlets whenever we want, and reproduce plants on our own schedule.
6 – Speed up the creation of cultivars
In the before times, cultivars were a bit hit-and-miss. You’d breed a plant, it had a fun variation, so you’d breed from it and *hope* that you could repeat your results. With tissue culture, the new plantlets created from that plant cell are clones of the parent, so you’re far more likely to get the same variations*.
*This isn’t as perfect as it seems. Variegation in particular is present at a genetic level, but is also determined, in part, by the plant’s, er, upbringing. Nature vs nurture strikes again!
7 – Create hybrids
Creating hybrids is big business in botany, and tissue culture speeds things up. Not only does it speed up the hybridisation (because you can do it all in a petri dish, rather than fannying around with brushes and pollen), but once you have a hybrid that captures the market’s interest, you can make a million of them from that one you made.
8 – Manipulate plant characteristics
Grow a tomato that’s extra sweet? Clone it. Make millions. Grow a tomato that produces twice the yield that it usually does? Clone it to make millions. Hybridize the two, and retire on your winnings.
Also, consider brassicas. One plant, a load of different vegetables – cabbage, broccoli, sprouts, etc etc… all made possible by manipulating different parts of the plant to grow in different ways.
9 – Create mutations
Ever wonder how they make seedless watermelons? Because…they have no seeds! They’re sterile! Surely, once they’re gone, they’re gone??
No, because they were created in tissue culture. Tissue culture is faster, more efficient, and less grubby than planting seeds and watching them grow. Keep one plant, and just keep harvetsing cells to grow more plants.
Now I’m wondering why watermelons with seeds still exist.
How to tissue culture plants
This isn’t something one can do in one’s home unless one forks out a buttload of cash. But here are the basic steps to tissue culture a plant:
(I’ve taken these from the orchid paper – there will be variances between plants and labs)
1 – Select your plant
The bit of the plant you use to tissue culture is called the explant. It can be whichever bit you want – node, root fragment, apical bud. Remember Haberlandt’s theory about plants being totipotent? He was right. Just pick a bit you like!
2 – Clean it
This is both simpler and more complicated than you’d think – a bit like scrubbing for surgery.
If you read the orchid study I linked to before, you’ll know that the first stage of this is…washing it under running tap water.
Then it’s soaked for half an hour in Polysorbate 20, which is worth googling if you have the time. It’s used for cleaning, binding, stabilising emulsions and a vast array of other, entirely unrelated things.
Then we wash our explant under running tap water again
Then we wash it in sodium hypochlorite for five minutes, then ethanol for two minutes, in a laminar flow hood, which is a sterile environment. I like to think they use those gloves that are attached to the hood like they do with babies in grey’s Anatomy.
Then they’re rinsed in sterile water and dried with sterile filter paper.
3 – Feed/house it
Then the explant is put in nutrient solution. It’s usually some kind of weird agar mix, so it’s a weird gel. Any OG vegans remember when all our gummy sweets were made with agar agar? Bad times.
I’m assuming it’ll vary from plant to plant. A TONNE of supplements are added.
4 – Keep it clean
All equipment is run through an autoclave (one of the many reasons I don’t think I’ll be trying it at home – I don’t have an autoclave) before use, and there’s a delicate balance that needs to be struck between light, humidity, and adding nutrients and stuff.
I imagine the dread of having to repeat the cleaning process makes getting this stuff right a bit more pressing.
5 – Harden it off
Once plantlets are formed (around three weeks for orchids, but I’m guessing it varies) they’re run under tap water and treated with fungicide. They’re put into potting medium – a mix of coir, litter (??), and clay (leca, do we think?), topped with spaghnum and put in a perforated polythene bag. in the shade.
Watered daily (I’m gonna assume they’re outside, in a nursery) and fertilised weekly with a 20:10:10 fertiliser.
My immediate thoughts when reading about this is how lucky we are to have people like Haberlandt and the people that developed these procedures.
If all humans were like me, we’d be living in caves crying about how hard life is, and how upsetting it is that we all keep dying after we cough. If the food was terrible I *might* endeavour to learn about, e.g. fire, but if there were mango trees around, the entire human race would laze around eating mangoes until we all died of, er, mango overdose.
Except mangoes wouldn’t taste the same because we’ve probably tissue cultured that deliciousness into them. See also bananas.
Thanks, botanists, we owe you a lot.