Any water plants release oxygen at night?

Hi.

I was reading about how some cacti, orchids, epiphytics, and bromeliads run counter culture and release oxygen at night. I was wondering if there were aquatic plants that did as well. (Submerged, emergent, floating) A quick goggle didn't provide anything useful. Since the above plants tend to be from the tropical regions of the world, my guess would be any aquatics that did so would be as well, so it's more of a long shot asking this question here. But, you never do know who might know what! One would think that such a plant would be popular with the aquarium folks.

The plants you mention have photosynthetic pathways adapted to minimize heat stress, which includes being able to continuously fix CO2 through special enzymatic pathways (in a million words or less...). The cacti use what's called CAM, crassulacean acid metabolism, and I doubt that aquatic plants need that. Other tropical land plants use the C4 pathway which allows them to conserve H2O during the day, not a problem faced by aquatic plants. Having said all of that, I honestly don't know what pathway is used by various aquatic plants. If you google this, I'd suggest something to the effect of "carbon fixation aquatic plants" or "photosynthetic pathway aquatic plants."

That's called crassulaic acid metabolism; the pores (stomata) are only open at night. It's mainly found in arid-land plants as it helps prevent water loss. As far as I know the only aquatic plants that use it are certain species of quillwort (Isoetes) from eutrophic ponds; it allows them to take in CO2 at night when levels are higher.

EDIT: Sorry, I was typing at the same time that Bruce was. I didn't mean to be redundant.

Edited by Newt, 01 July 2008 - 07:06 PM.

I love smart people!

Thank you gentlemen! I will try goggling CAM. And Newt, no worries. I find the older I get the more repetition I need, and since getting younger isn't an option, you can repeat to me all you want!

Thank you gentlemen! That made for some interesting reading!

Would you consider eutrophic a term interchangeable with stagnant, or is there a slight yet important difference?

I ask, because we have a stagnant pond at our school with native frogs in it. I've discussed this pond with a variety of folks. One retired biologist even helped me collect some plants for it. While he was very kind and helpful, I didn't walk away feeling I was doing the right thing. The plants have survived versus thrived. Part of me thinks, if it ain't broke, don't fix it. If the frogs have been there for decades and they're still breeding, it ain't broke. Part of me wants to plant plants. It's finding the right plant. There isn't much I can do to change the water conditions, it is what it is, schools are notorious for neglect. While it is temping to set up a pump, it just isn't realistic when there is no one there to check on it half the year (counting weekends.)

I learned there are quillworts native to here, now all I gotta do is find them! Wish me luck!

Stagnant simply means not moving, no water exchange, while eutrophic specifically means water with elevated nutrient loading. You can have a eutrophic river (the Mississippi) that's not stagnant, while you could have a stagnant rain pool sitting in a basin that isn't eutrophic. So, they are different although often can both be used to describe especially a shallow pond.

Good luck finding the quillworts! It definitely helps to have an experienced botanist with you; quillworts are not very distinctive looking and are hard (for me at least) to distinguish from the various sedges, rushes, and so on also found in aquatic habitats.

Before you worry about it too much, see if you can borrow a probe that can detect DO levels. Your pond probably has adequate oxygenation for the frogs as is, and the quillworts are unlikely to help much. By all means get them for their own sakes, as they fascinating primitive plants, but don't worry too much about the frogs. Even the tadpoles can gulp air if they need to; I see them doing it all the time in our soupy southern swamps (which I'm willing to bet get much warmer and anoxic than your pond).

Mander,
Being on the east coast, I'm not sure my go-to plants for your situation would be appropriate species. I suggest seeing what the Oregon Native Plant Society might have on aquatic gardening. I noticed that their archived bulletins are on their website.

In general, I would look for some emergent shoreline plants. Here, I would think of lizzard's tail, native iris, pickerel weed, various Eleocharis species, and Hydrocotyle species. Native water lilly if the pond is big enough. Perhaps the Oregon Native Plant Socity has some analogues for these.

Isoetes species are sensitive. I do not recommend collecting them unless you can really keep an eye on them and are a good gardener. While they don't seem to be protected in Oregon, they are rare nonetheless. I have kept some before; they are particular in their requirements. I have never found them in eutrophic environments, but Carolina Bays, along shallow, continuously flooded areas in low nutrient systems. The most I have ever seen were the result of a seed bank study where cold treatment of the soil seemed to prompt the spores to germinate.

Depending on your pond, low oxygen may not be a bad thing. There are a number of species that rely on there not being fish in an environment, such as frogs and salamanders that breed in vernal pools. Anyway, assuming yours is the typical school pond, I would have them stop mowing around the edges, as fertilizers and other contaminants need to be filtered out of the runoff before they get to the water. Also, check to see that they are not herbiciding around the edges - some people do that if the lawnmower gets bogged down.

Thank you, Bruce. That's actually a huge difference. I went back to look and the diagrams I was looking at weren't wrong, just skimmed over certain details. I''m inclined to think a little Venn diagram would have my pond as both! But we shall see.

Thank you , Nate. I need all the luck I can get! My knowledge is limited to "sedges have edges and rushes are round." Which is right about as often as "i before e except after c and words in that are foreign like neighbor and weigh." Anyway, the photos I saw, it shouldn't be too difficult to distinguish a quillwort, it looks sectioned like a horsetail, to which it is related.

Thank you, Pat. I often do the native plant sales, but aquatics are a whole 'nother story. I am told that I'm a decade (or two) late looking for native aquatic plants. There was no money in it, so few if any do it, except to large scale buyers like the State. And yes, you're right, from what I've read, the isoetes on the east coast are very, very site specific. But, if one is to believe the internet, there seems to be one native here that might fit the bill. And yes, I think I will grow it at home first before planting at the school, to see how well it does.

Having installed and/or helped maintained seven or eight school gardens, I have become very selective as to what I will do at school sites. This one, has me heart and soul. It is an interior garden that has been allowed to be blissfully ignored in a positive way. No pesticides, no hackers, no nothing. I put in about a hundred natives a year ago spring and plan to do more this fall. I'd like to put salamanders in the pond, for diversity, but it has yet to happen.