Dimorphic pollen in gourd

Bottle gourd – a common summer vegetable is a spreading vine that climbs with the help of stem tendrils on the hedges and supports. It has been raining ferociously these days, so the vine in my neighbourer’s  garden had spread on my wall. I could make out the palmately lobed leaves covered with hair giving a rough texture.

The bottle gourd flowers are dioecious, borne singly in the axil of the leaves, the males on long peduncles and the females on short peduncles. The flowers are white in colour with spreading petals. The ovary is inferior and is of the shape of the fruit.

I plucked a flower and it was a staminate one. Male flowers have stamens grouped together in the centre of the flower. The stamens have  short filaments and sigmoid anthers. On cutting a longitudinal section the anthers could be clearly visible. The anther lobes were teased gently to release the pollen.

I was viewing the pollen and clicking images and gently moving my foldscope to capture sharp and clear images, and then a particular focus amazed me. Foldscope had unveiled a focus showing two different types of pollen present together. One type of pollen were light coloured, spherical in shape and  tricolpate, while the other type of pollen were ellipsoidal in shape and dark in colour with striations or ridges present on exine.

Light coloured, spherical tricolpate pollen 

Dark coloured ellipsoidal pollen


6 Comments Add yours

  1. varuni says:

    Dimorphic pollen is pretty rare (and cool)! Did the two types of pollen come from different types of anthers? Is this something you saw if multiple flowers? You should check and see if this has been reported in other members of the gourd family.

    (I suspect you are either observing pollen of another plant that was brought there by a pollinator or that the two different types of pollen you see are at different stages of hydration — you can check this pretty easily.)

    1. Rahul_SD13 says:

      Hello Ma’m. I separated out one anther and gently teased it. I took only one flower, the one visible in my post. My teachers taught to patiently observe a slide at different loci. I did the same and saw two different pollen at more than 3 loci within one slide. My teacher has asked me to perform pollen sterility using dyes.
      In literature, family Cucurbitaceae and Mimosoideae do report dimorphic pollen in some cases.

  2. varuni says:

    Thats really interesting! I’ll try to look out for it next time I find a Cucurbitaceae or Mimosoideae flower. I wonder if this is an evolutionary adaptation like in the Nagalingam flower (https://microcosmos.foldscope.com/?p=37955)

  3. laksiyer says:

    Quite remarkable. The shapes are really quite unrelated it appears. It brings out an issue that I had been thinking about for some time that pollen shapes quickly converge to a few types and this dimorphism suggests why it isnt too difficult. The only one that has been consistently of the same shape in my expolorations are the compositans.. Looking to catch exceptions there too. If there are none, it poses a good biological problem.

    1. Rahul_SD13 says:

      Thanks Laksiyer sir and Varuni ma’m. Reading the discussion on the post, I thought of reviewing my observations. Repeated slides prepared from flower obtained from the same plant confirmed pollen dimorphism in gourd.

  4. varuni says:

    So, firstly, I’m not sure we mean the same thing when we talk about “dimorphic pollen”.

    It seems like in this post (as well as the in newer one: https://microcosmos.foldscope.com/?p=62343) there is a very clear line (which looks likes a line between solution and not) that separates what you are calling the two “types” of pollen. I can imagine that one type can be morphed into the other with application (or removal of) water. While this may seem like just semantics, from my understanding, dimorphic means something quite different from the morphing of pollen shapes in different states of desiccation. Also, as far as I have observed (https://microcosmos.foldscope.com/?p=40088) and read (https://www.paldat.org/search/genus/Cucurbita) Cucurbitaceae does not have dimorphic pollen.

    This is not to say that Cucurbitaceae/Mimosoideae do not have dimorphic pollen — its just that these observations do not seem conclusive. Do these pollen grains come from different anthers? Do you see the two types of anthers in every flower? Maybe you can try to soak all the pollen in water and see if this difference still exists? Maybe try to dry them out and see if this difference still exists?

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