Foldscope Day 1: How a Citrus Tree Makes its Scent

Hello there. I’m Aatish, a science blogger, and I’m super excited to get my hands on a foldscope and connect with the foldscope community here.

I assembled the kit yesterday, and then plucked a leaf from a Mandarin orange tree in my backyard at home in Delhi. According to this source, this plant grows widely in India and was apparently brought here from China in the 8th century.

mandarintree

Here’s a closer look at its leaves.

mandarinorange2

Beautiful, isn’t it? I love this tree. The first thing I noticed on plucking the leaf is its wonderful citrus smell. I cut out a small chunk of the leaf, stuck it on a slide, and slipped it under the foldscope. Here’s what I saw.

IMG_7079

You’re looking at the edge of where I cut the leaf. Here’s a closer look at the surface of the leaf (towards the top right.)

citrus leaf dots

I was kind of mesmerized by this, and tweeted out a question. (Click the video to see what I was looking at.)

The thing that puzzled me were those holes. There are two kinds, the little ones, and the big ones that seem to almost cut right through the leaf — you can see the light shining brightly through. I was curious what was going on here. At first I thought these were stomata (the air-holes through which a leaf breathes), but Manu pointed out that those are much smaller. So that wasn’t what I was seeing.

And then a friend on twitter solved the puzzle:

Isn’t that neat? So the dots I’m looking at are the glands from where that delightful citrus scent emanates. The technical term for these structures are pellucid dots, so if you want to read more about them, that’s the term to google for. And you can read more here about the chemistry of this scent, and the various chemical compounds that create this unique fragrance.

I’m really happy with my first day using the foldscope. This is my first time owning a microscope (something I’ve long wanted to get my hands on) and the experience is kind of blowing my mind.

Questions

Here are some more questions I was left with after this experience:

  • What are those larger holes? How are they different from the little dots?
  • Could I see the stomata (air-holes) of this leaf if I used the high magnification lens? I tried this out and took a short video, but found it a little hard to focus and couldn’t get a clear sense of what I was seeing. Need to work on this.
  • How similar are these gland dots in different citrus leaves? There’s an orange and a lime tree in my backyard as well, I could try checking out their leaves too…

Looking forward to hearing your thoughts, and to more exploring!

3 Comments Add yours

  1. laksiyer says:

    Really cool pics. These are a kind of trichome with a transparent shell. One thing would be to study the density of these glands between different species of citrus. An epidermal peel might be easier to see stomata. Did you check the ventral (lower) side. That is where the stomata of ctrus leaves are.

  2. Manu Prakash says:

    Wonderful to see this – I love the cascade of events. It’s so much fun discovering things for yourself with gentle nudges from the inter webs. This makes an impression on the mind like nothing else. It’s your discovery; and everyone else’s – such a joy to watch this here.

    Another aspect of the glad cells would be is to watch the secretion “live” – say if I wanted to know how much of this “oil” is produced per day. Just like my stomata video (https://microcosmos.foldscope.com/?p=8159) – but leave the microscope and your camera/iPod/phone mounted on the tree overnight. I wonder if you could watch the secretion grow over time – would be incredible to know what rate chemical synthesis takes place (which is a molecular process) by just watching microscopic growth. Chemical synthesis is usually estimated in bulk measurements – this would be single cell production of some kind.

    Also; enjoy those lovely oranges 🙂 you might find some Indian species of drosophila larvae in the rotting fruits – our original addiction to alcohol.

    So jealous you are in India – I just returned back. Maybe – you can do another post on terminates. @Laks (foldscope super user) and I have an incomplete story with termite guts – believe me; it’s going to be incredible 🙂

    Start by finding these guys on tree trunks. See my tutorial for collecting termites here: https://microcosmos.foldscope.com/?p=11116

    Cheers
    Manu

    Cheers
    Manu

    Cheers
    Manu

  3. Manu says:

    Wonderful to see this – I love the cascade of events. It’s so much fun discovering things for yourself with gentle nudges from the inter webs. This makes an impression on the mind like nothing else. It’s your discovery; and everyone else’s – such a joy to watch this here.

    Another aspect of the glad cells would be is to watch the secretion “live” – say if I wanted to know how much of this “oil” is produced per day. Just like my stomata video (https://microcosmos.foldscope.com/?p=8159) – but leave the microscope and your camera/iPod/phone mounted on the tree overnight. I wonder if you could watch the secretion grow over time – would be incredible to know what rate chemical synthesis takes place (which is a molecular process) by just watching microscopic growth. Chemical synthesis is usually estimated in bulk measurements – this would be single cell production of some kind.

    Also; enjoy those lovely oranges 🙂 you might find some Indian species of drosophila larvae in the rotting fruits – our original addiction to alcohol.

    So jealous you are in India – I just returned back. Maybe – you can do another post on terminates. @Laks (foldscope super user) and I have an incomplete story with termite guts – believe me; it’s going to be incredible 🙂

    Start by finding these guys on tree trunks. See my tutorial for collecting termites here: https://microcosmos.foldscope.com/?p=11116

    Cheers
    Manu

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