Field of Science

A Sporophyte Gone Wild

What happens when a moss sporophyte's calyptra does not detach properly? Really odd development! I came across this sporophyte in one of my Funaria hygrometrica cultures recently.

Calyptra Recap: The calyptra is a small cap of gametophyte tissue that covers the moss sporophyte apex during its development. It is necessary for proper capsule and spore formation in moss sporophytes. Studying the calyptra-sporophyte interaction was the focus of my dissertation research. (You can read more about my main findings here. The calyptra has a cuticle. - The calyptra cuticle develops early relative to the sporophyte cuticle.)

So, this really odd development. It looks like the calyptra did not detach from the rest of the leafy gametophyte properly. Usually there is a line of dehiscence at the bottom that allows the calyptra to separate as a distinct cap. In this specimen the calyptra appears to have split open down the side with the sporophyte continuing to grow. As usual, sporophytes without their calyptra on top do not develop a capsule at all and instead produce an obconic-shaped sporophyte.

On this sporophyte, the apical region and seta meristem both appear to have turned brown and died. Also, there is a funny little projection of tissue sticking off the right side of the thickened stalk. (There is a zoomed-in photo below.) I don't think that I have ever seen anything that looks like this on a sporophyte before!

What is it? Is it branching? Maybe. Is it the beginning of a leaf? Probably not. It would be really cool to section it and see what the internal anatomy looks like. Does it have  central strand tissue going out into it? It looks pretty small so probably not. I wonder if I saved this sample in the lab after taking some photos of it so that I can process it for some anatomical study. Either way, I think that it is some pretty cool morphology to think about!
On the Left: An close-up of the sporophyte breaking through the side of the not detached-calyptra. On the right: An up-close view of the tissue projecting from the sporophyte.

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