[Science Room Blunders] The story of how I taught that shiso leaves were 'stomata' because they sparkled, only to find out they were actually something else

The 'observation of stomata' is conducted in the biology unit for second-year junior high school students.
It is a classic experiment using a microscope, isn't it?

While using dayflowers or spiderworts is the standard approach, isn't it the nature of a science teacher to want to try various things, wondering if other easily accessible plants might work as substitutes?

Actually, a few years ago, I used common 'shiso' (perilla) leaves and ended up in a major classroom disaster and failure.

With a sense of self-reproach, I would like to share that 'blunder' and the real identity captured by the microscope with teachers across the country.

🔬 The trap of 'The back of the leaf is shining like crazy!'

At the time, I suddenly thought, 'When I peel back the underside of a shiso leaf, there are lots of shiny, round particles. Could this be a dense cluster of stomata!?'

I immediately set it up under the microscope and looked, and this is the field of view that spread out before me.

The whole thing glowed a bright yellow-green, and round, crater-like particles were lined up one after another.

I was so excited at the time. I confidently taught the children, 'Look, the stomata are lined up so beautifully on the back of the shiso leaf!'

I even smugly connected it to textbook knowledge, saying things like, 'See, they really are more common on the back of the leaf!'

However, after class, when I increased the magnification of the microscope and observed it very carefully again, cold sweat ran down my back.

'...Huh? I can't find the lip-shaped 'guard cells' anywhere?'

💧 The shocking reveal: It wasn't stomata, it was 'something else'

After being curious and thoroughly researching it again, a shocking fact came to light. The true identity of those shiny, round particles that I and the children were desperately looking at through the microscope. They were not stomata, but 'glandular scales' that store the unique aromatic components (essential oils) of shiso, commonly known as 'scent orbs'......!

As proof, here is a photo I captured even more clearly.

Please take a look. Between the vivid pink leaf veins of the red shiso, beautiful, plump, dome-shaped capsules that look like glass beads or water droplets are floating three-dimensionally.

Yes, we weren't looking at stomata at all; we were making a huge fuss over 'shiso scent capsules' and calling them 'stomata'! I am so sorry, kids...!

By the way, my intuition that they were 'overwhelmingly more common on the back of the leaf' was the only thing I got right. It seems it was a survival strategy for the shiso: by reinforcing the defenses on the back of the leaf, it keeps scent components (repellents) in ambush to prevent insects from eating it. It was a confusing trap that they miraculously matched the characteristics of stomata (lol).

Here, I would like to add a little supplement regarding the morphological differences for my fellow science teachers.

In the first place, 'stomata'are, as you know, 'gaps (holes)'surrounded by two guard cells. In contrast, the'glandular scales'that the microscope was capturing are a secretory tissue (a type of hair) derived from epidermal cells, and are 'three-dimensional domes (capsules)'filled with essential oils.

In other words, in an experiment where I should have been looking for 'holes,' I was desperately observing the exact opposite: 'protrusions' (lol). No wonder I couldn't find those lip-shaped cells no matter how hard I looked.

Well, after that failure, I decided to use these shiso scent balls (glandular scales) as a hook for my students in class.

I place a shiso leaf in the palm of my hand and slap it vigorously from above with a 'Pop!'

Then, in an instant, the refreshing, pleasant scent of shiso spreads. The kids are overjoyed, shouting, 'Whoa!' and 'The smell changed in an instant!'

If I prepare several shiso leaves and give them to the kids who don't mind the smell of shiso, telling them, 'You can slap them yourself,' it's funny to see them observing through the microscope while hearing the sound of hands slapping 'pop, pop' everywhere (lol).

To explain this rationally,the impact of slapping with your palm causes the glandular scale capsules on the back of the leaf to burst all at once, releasing the essential oil inside into the air in one go. (Of course, if you look at the leaf under a microscope after doing the 'pop,' the dome-shaped scent bags are crushed and gone. It's truly a life-or-death fragrance...!)

Being able to have this kind of'real experience using the five senses'is one of the joys of the science lab, isn't it?

👑 Conclusion: I wandered off the path, but the classic way is still the best

After this painful blunder, I learned a great lesson: 'There is an overwhelming reason why textbooks push dayflowers so hard.'

Once again, here is the view through the same microscope looking at the classic dayflower.

...It's self-evident, isn't it? (lol). The epidermis is easy to peel off, the cell arrangement is straight, and above all, the lip-shaped guard cells and the 'opening and closing' of the stomata are so clearly and uniformly visible. As expected, the dayflower was the classic and strongest teaching material.

Assumptions and wandering in the science lab can be nerve-wracking, but I also feel that the thrill (and deep reflection) of 'So that's what it was!' when you re-observe at high magnification is a real pleasure that only a science teacher can experience.

💬 To all the teachers struggling every day across the country

The reality of the science lab is that things don't always go according to the textbook, right? If you have any 'actual failed experiment episodes' or 'history of wandering' like this 'shiso scent ball incident,' please let me know in the comments!

Also, I am looking forward to hearing any rational and reliable stomata observation techniques that only teachers would know, such as 'We use this for everything except dayflowers!'

Let's bring our collective wisdom together and update our lessons to be even more fun!