Stomata in succulent leaves

May 24, 2020 • 10:57 PM UTC

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TCIS Outreach

We are a group of students, volunteers and staff working with TIFR Hyderabad's Science Education and Outreach program: http://www.tifrh.res.in/~outreach/

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At the peak of summer, the potted plants in my balcony get an extra dose of sunlight! One of these plants is the Ceylon spinach ( Talinum fruticosum ) . I noticed that during summer its leaves are curled up most of the time. I guessed the excess of sunlight or wet soil may be the cause.

I wanted to observe the stomata of its leaves, so I peeled off the lower epidermis This is easy to do as the leaf is soft and thick (the nail polish method is not required).
Just as I have done countless times with other leaf peels, I placed this peel with the help of cellotape on a glass slide to view under the Foldscope. Alas, it wouldn’t work! The tape got foggy in no time to give a (beautiful) cloudy image with some flowing particles!

For the second trial, I used a coverslip on the lower epidermal peel. Since the leaves of the succulent are juicy, the fluids can be seen flowing across, with some live microbes making their own way through the flows!!

For my third trial, I added a drop of water on the sample and covered it with a coverslip. Voila! The clarity was enhanced and I could see green balls (what do you think they are?) running helter-skelter and the stomata can be seen with good clarity.
If we observe carefully the second and third videos along with the sap some other granules are moving freely in various directions. Are they microbes? Can anyone help to identify them?

Stomata in Ceylon spinach leaf

This episode sparked my interest to observe stomata in succulent leaves. So I took up another common plant, the Aloe Vera , which has long fleshy leaves.

The epidermis could be peeled off easily. I could see the flowing sap but not the stomata. So I observed the sample under a drop of water.

Here they are! Since Aloe vera is a xerophyte, there are fewer stomata and like other monocots they are in a systematic pattern.

Soon after, I started observing the stomata of green leafy vegetables that are part of our regular diet. We generally add these greens to dal, curry or chutney. All these plant leaves are juicy. Peeling their epidermis is easy and now I have learnt that adding a drop of water greatly improves the clarity of images.
Malabar spinach (Basella alba)

Wow! The stomata of Malabar spinach are open!

Here is Spinach dock or khatta palak ( Rumex vesicarius ). In this plant, I found open stomata when the leaf was fresh! When the leaf was dry (after 3-4 hours) the stomata were closed!

Open stomata of ‘khatta palak’.

Purslane leaves or gangavalli ( Portulaca oleracea ).
Did you know that this green was endorsed by Mahatma Gandhi? Purslane was his favourite green vegetable because of its high nutritious value. Read more here .

Purslane leaves have particularly large subsidiary cells surrounding the guard cells of the stomata.

I have yet another interesting plant in my balcony called Brahma Kamalam ( Epiphyllum oxypetalum ) which is a cactus species. I planted this for its unique flowering pattern and exquisite fragrance! The plant flowers just once a year at night, and the flower wilts away by dawn.

The primary stem of the Bramha Kamalam is terete and the secondary stem is like a leaf with a lobed margin. On the margin there are leaves.

It was very hard to get the epidermis peel, so I had to get back to the dear old nail polish method! The leaf was covered with a waxy cuticle so I scratched the epidermis with a blade! I found very few stomata in this plant too!
I found a great way to observe the stomata of juicy leaves: just add a drop of water to the sample, and place a coverslip on it. The leaves that I observed all had irregular arrangements of stomata except Aloe vera (which is a monocot). The few stomata of Aloe vera were arranged in a staggered parallel pattern, probably along the parallel venation typical of monocots. In my sample of leaves, with the exception of Aloe Vera and Epiphyllum , all the other juicy leaves had plenty of stomata.

This was the first time I saw a stomatal pore, which was an exciting experience!! Thank you, Foldscope team!
Cheers,
Ashalatha