Saturday, November 14, 2009

Question for the Hive Mind: Cycas revoluta weird growths

Life has become momentarily unmanageable, due to a combination of factors, some of which are not in my control, so there will be no Saturday afternoon Nina picture, and the posts for today and tomorrow will be a little lightweight. Sorry about that. Something to ponder in the meantime: what exactly are these things I found in the soil of my Cycas revoluta? I think they're attached to the plant, and therefore probably part of the roots (or maybe some kind of symbiotic nitrogen-fixing something?), but I don't remember seeing anything like this when I initially repotted the plant, plus they're strange, so I thought maybe I should ask the collective.


our friend Ben said...

Well, I can see why Nina might need a break; she's still probably exhausted after that interview! As for those nodules, do you think it's possible that cycads have a symbiotic relationship with a beneficial microorganism like the micorrhizae on legume roots? Who'd'a thunk?

MAT kinase said...

It's hard to say without a size reference. Some types of mycorrhizae form club-like growths surrounding roots, but these would be really tiny and surrounded by a thick web mycelium. They're also a lot smaller than I would guess those things are (take a picture with a penny in it?). I've never heard of mycorrhizae occuring in cycads or ferns but it may just be because no one has looked. They're extremely common in conifers though.

Were they growing on/near the surface of the soil? (probably a slime mold or little fungal fruiting bodies) Were the deeper? Were they attached to roots or the base of the plant itself?

If you have time to take a higher-res picture (maybe one zoomed in to the growth and one zoomed out to the plant) I might recognize what it is.

very cool!

MAT kinase said...

i was looking at it again, and some of them look like little mushroom caps with hairy stalks. let us know if they expand into full size ones!

Diane said...

Cycads are, AFAIK, the only cycad that can fix nitrogen, and they do it through a symbiosis with cyanobacteria, not the regular old Rhizobium-type bacteria like with legumes and such. So, it's possible that your nodules are cyanobacteria-made. It's pretty unusual and interesting to see nodules on a houseplant. The roots or soil must have been inoculated by the original grower. (I would blame the death of my cycad on lack of nodules, but I think the massive infestation of scale had more to do with it!)

I did find a couple papers on arbuscular mycorrhizae associations with certain cycads. Like MAT said, though, mycorrhizae are not usually so lumpy and obvious.

Now I need to stop typing the word "cycad" because it looks less and less like a real word every time.

Thomas said...

I'm wondering if they are mushrooms - the little bright-yellow numbers that come up in greenhouses and terrariums sometimes? (Yellow Lepiota?) I had them popping up in a large terrarium once. They developed fast (days), but were short lived, and eventually stopped appearing. They were actually kinda pretty, for mushrooms.

mr_subjunctive said...

They're not mushrooms, unless they're really lazy ones: they've been basically the same size for weeks now.

I'll work on getting a picture that shows the size better.

Diane said...

Gah, I meant to say cycads are the only *gymnosperm* that fixes nitrogen. No wonder it seemed like I was typing "cycad" too often.