annuals vs. perennials - The Planted Tank Forum
 
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post #1 of 15 (permalink) Old 07-19-2007, 02:19 AM Thread Starter
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annuals vs. perennials

It is scary how often I look up and say "D*mn! I don't know squat about this hobby!" Today was one of those days...

I was reading a recent issue of one of my favorite periodicals - Scientific America - and came across an article about the long term value of mankind returning to the use of perennial crops vs. the domesticated annual crops we use today. The concept is simple in principle - why grow part of the year when you can grow all year? And - why rip up nutrient sequestered roots - only to replace with fertilizers - when you can just rip up the tops of perennials and let their roots continue to nurture the soil?

You can read it all in Scientific American - Aug 2004, V297, Number 2, pp 82-89...

Anyway, it got me to thinking about our own soil uses, and cause me to wonder...

Are all aquatic plants perennial (growing year round?). Or might there be a whole part of the hobby that I'm missing? One that requires fertilization and annual seeding?

As far as I know, this hobby depends on plants that grow by runners (needing no propagation), or is done by replanting of cuttings. But as far as true generational life-cycles go, it (like annuals) is beyond the scope of our hobby? Or am I missing something.

I hope to hear your thoughts...

Steve - 33g reef and a 180g planted in need of a re-scape.
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post #2 of 15 (permalink) Old 07-19-2007, 03:00 AM
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the problem with perennial vs annual crops is with soil errosion with yearly tilling. It's funny how all our grains are annuals and fruits are pernnials.
I think some food company or university is trying to selectively breed a perennial grain right now but they're still generations away from something practical.


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post #3 of 15 (permalink) Old 07-19-2007, 03:18 AM
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well, in nature, the plants are under their "ideal" conditions, and they set seed and such. i beleive the stem plants rarely set seed.

melon sword, i know from experience, sets seed and plantlets. when grown emmersed, it does extremely well, and sets seed from its orchid like flowers. it's all a matter ofcircumstance. our hobby(aquariums) only focuses on the aquatic parts, there are also emmersed and even terrestrial parts of a plants life cycle, in fact, many of our plants aren't mainly aquatic, they just happen to venture out into the water, or live in the water occasianally. Anubias sp. lives on waterfalls and such, mostly just growing with the presense of very high humidity, yet it grows fine underwater.

under the water, most plants will not seed, unless the flower can reach the surface and be fertilized.

And you are overlooking the fact that alot of aquatic plants grow in places where there is no need to be annual, the water temperature generally stays around the same, or the plant can handle the cold. therefore there is no reason for the polant to die and seed. some plants die back(Ie: waterlillies), and come back as the same plant next year.

One of the only real reasons for seeding, that i see anyway, is to increase biogenetic diversity, so that all plants aren't clones of one another. this also opens the doors for evolution, adaptation, and diversity.

So, i don't think the "scope" of our hobby really catches the complete life cycle of the plant.

-Devin-
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post #4 of 15 (permalink) Old 07-19-2007, 06:03 PM
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Steve, I've often wondered the same thing. I'm confident in saying that most (at least around here) are perennial. During the winter, I noticed they die back to the substrate level. However, next year, they seem to pop up in the same places.

In college....so no aquariums for a while.....
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post #5 of 15 (permalink) Old 07-20-2007, 12:42 AM Thread Starter
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Well... thanks for the responded folks.

It's kind of an off the wall question I know, but it seemed an interesting subject.

I've had my own set of flowering plants, but - like the anubias mentioned here - none of them were "true" aquatics. Frankly I've not pulled out a reference book to confirm this, but I suspect few of the plants we use in this hobby are.

So what about the "true" aquatics - plants that have no emersed form and cannot survive out of water? Are those all perennial? And do true aquatics have any form of sexual reproduction?

Steve - 33g reef and a 180g planted in need of a re-scape.
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post #6 of 15 (permalink) Old 07-20-2007, 02:36 AM
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Anacharis flowers, i know that much.
I like to think of most aquatics of more of "evergreen".

-Devin-
Steve irwin- a father, a hero, a memory now. -We'll miss you mate
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post #7 of 15 (permalink) Old 07-20-2007, 02:48 AM
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I don't know if there's such a thing as 'true' aquatic plants. There's no sexual reproduction scheme that takes place underwater.. They all shoot out into the air if underwater for insects to pollinate.. Even hornwort flowers.

Java ferns, a more primitive plant, have a different reproduction scheme though... They have spores.

Somebody who studies this stuff should chime in.


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post #8 of 15 (permalink) Old 07-20-2007, 06:28 AM
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Java fern is not meant to grow underwater. If you've ever seen pictures of it, it grows quite emersed. It just so happens to grow underwater.

True aquatics, like Potamageton, Cabomba, and Egeria, seem to all be perennial. They simply pop up from underground root systems every year when the weather starts to warm. I've witnessed it here in central Illinois.

In college....so no aquariums for a while.....
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post #9 of 15 (permalink) Old 07-20-2007, 04:13 PM
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Interesting post, Scolley! It's got me to thinking.

Relatively speaking, there are very few true annuals, and there has long been a debate about whether even those are true annuals in the strictest sense of the definition. To be a true annual, a plant would have to sprout from a seed and die out completely, roots and all, within one year, even when the optimum growing conditions don't change. If this life cycle takes more than one year, they're called biennials.

Most plants thought to be true annuals are vegetables such as beans, squash, and corn, and some wildflowers. Then there are another group of plants that are grown as annuals, but really aren't, such as tomatoes and bedding begonias. These are called tender perennials. If their optimum growing conditions didn't change (including no killing winter freezes that extend down to the root zone), begonias and tomatoes would continue to grow for years. I have a pot of regular old begonias, the kind you get cheaply in six-packs absolutely everywhere in spring, that I've had for four years. I just put it in the greenhouse in winter. Some easy-to-propagate tender perennials are grown as annuals because it's just less trouble to let the old ones die and replant next year than to dig and overwinter them.

Keeping this in mind ~ the relative scarcity of true annuals plant-kingdom-wide ~ and thinking of the mechanisms that forced some plants to evolve into true annuals, I'd say there are very few aquatic annuals as well. Of course this is only supposition on my part, but if you think about it, true annuals developed because of a need for a dormant period, imho usually triggered by cold temperatures or dry climates in part of the year, and most aquatics aren't exposed to that. Water doesn't change temperature as easily/drastically/much as air/land does and most bodies of water don't dry up seasonally either. Therefore, I'd guess that most aquatics haven't had a need to evolve an annual life cycle to survive as a species, so there aren't that many if any.

Again, this is only supposition on my part since I haven't ever really thought about it until you asked this (interesting and thought provoking! ) question. And it's not even taking into account the difference between aquatic and true aquatic, or completely submerged true aquatic or partially submerged true aquatic (a la water lilies), or...

If you want to find any true annual aquatics just for grins, I'd concentrate my research efforts on natives of areas where the bodies of water do drastically change seasonally. Seems plants in those areas would have a reason to evolve that way.


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I was reading a recent issue of one of my favorite periodicals - Scientific America - and came across an article about the long term value of mankind returning to the use of perennial crops vs. the domesticated annual crops we use today.
That's a basic tenet of permaculture and is a quite interesting subject. Permaculture is basically an idea where humans' needs (food, shelter, etc.) are interwoven into a sustainable, permanent and ecologically sound way of living. Many perennials are used in this system since it just makes sense ~ not having to replant all your food plants means less work for more food, having perennials to shade your house means less energy output for heating and cooling, etc. If you want to know more about the plant side of it atleast, you can visit Plants for a Future or Google up "Permaculture" for an idea of the full permaculture movement ~ loads of sites about it out there. Interesting stuff.

Now I'm going to keep an eye out for that issue of Scientific American. That article sounds like one I'd like to read. Thanks for the tip, Scolley!

~ Linda ~

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post #10 of 15 (permalink) Old 07-24-2007, 12:11 AM Thread Starter
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Wow Linda! What a great reply! Thanks. :-)

I love your discussion of true annuals. And your tip about restricting my research to places that drastically seasonally seems like a good idea... but wouldn't that encourage plants to not be true aquatics? Having a emersed form? Or am I missing something?

Either way, you post is why I love this place... ask a good enough question, and some well informed people are likely to show up! Once again I'm humbled by my lack of knowledge, but am happy to post at a place where there is such a deep well of knowledge to tap. Thanks!

Steve - 33g reef and a 180g planted in need of a re-scape.
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post #11 of 15 (permalink) Old 07-24-2007, 01:55 AM
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Originally Posted by scolley View Post
Wow Linda! What a great reply! Thanks. :-)
You're sure welcome! I'm enjoying this discussion myself. I like exercising my brain and thinking about stuff like this, and the questions raised and ideas presented in this thread sure are making me think.

Quote:
I love your discussion of true annuals. And your tip about restricting my research to places that drastically seasonally seems like a good idea... but wouldn't that encourage plants to not be true aquatics? Having a emersed form? Or am I missing something?
Yes, you are right ~ that would surely encourage plants to not be true aquatics. That's probably exactly why most of our aquatic plants aren't true aquatic-only plants. But it's a definite possibility (a probability actually) that at least a few plants wouldn't have been able to make the transition to emersed growth. Those plants had a "choice" ~ use another mechanism to keep the species going (such as seeds) or become extinct. Some of them adapted and some didn't.

It's amazing the number of different ways plants have evolved to "hang in there". There are plants that never stop growing no matter what time of year, plants that go dormant in winter by dying back to the ground and re-emerging from their rootballs (or corms or tubers or bulbs) in spring, plants that go dormant but just lose their leaves then sprout them anew in spring and some plants that might go dormant but don't even lose a bud. There are plants that propagate themselves by offsets of bulbs, runners sent out from the mother plant, rooting from a branch that touches the ground, sprouting from a piece of root (not a bulb, corm, etc. ~ just a piece of root severed from the mother plant) and even some that will sprout roots from a small piece of leaf! Incredible.

And seeds! The different mechanisms that seeds use to "know" when to sprout is just amazing. Some need a certain temperature, some need a certain day length (yes, some seeds can tell time! ), some need a long wet monsoon. Some will lay in the ground for years until they are uncovered (as by plowing) and sun hits them for just a split second, and that's all that's needed for them to sprout, even if the plowing immediately covers them right back up. That's it ~ just a split second of light! Amazing.

And did you know there are seeds for certain plants that must hang around in their environment for years before sprouting to allow the weathering of their tough seed coat? Then, when the seed coat's thin enough and conditions are right for them, they sprout. And it's individual to the seed even ~ some weather faster than others of the same species. This appears to be a mechanism developed to allow the species to survive despite frequent drought years ~ the sprouting of the seeds would be staggered, so the ones that sprouted in year one of an extended drought wouldn't make it, while year four seeds would since the rains would come back by then. Lotus is one, the big pond lotus ~ Nelumbo spp. And there are others and they're not as uncommon as you think ~ some hard-shelled nuts are that way, though most nuts' shells probably developed their hardness more as a safeguard against getting eaten too easily by wildlife.

And think about that for a bit ~ that nuts developed such a hard shell to keep from being eaten. Imagine ~ if there were no such thing as squirrels, it'd probably be a helluva lot easier for us to eat walnuts.

Here's a neat story about the tenacity of seeds~ A few years ago, I tilled an area out here that hadn't been tilled in twenty years. There were NO unicorn plants (Proboscidea louisianica) growing within two hundred feet of that area for that entire twenty years, and only a couple-three plants growing anywhere on the ranch during that time. Yet, once that area was tilled, the unicorns popped right up en masse. The seeds are too heavy for them to have been blown or washed into this spot, and there isn't a luscious "fruit" for the birds to eat and therefore spread them (they're spread by those "talons" on the seed pod that grab ahold of an animal as it goes by). Those seeds laid there in that ground until I tilled it, watered it and fed it ~ twenty years after they formed. Incredible.

Can you tell I have a thing for seeds? Plants of all types, really. And Mother Nature in general. I tend to go on and on and ON when talking about them. Sorry.

Quote:
Either way, you post is why I love this place... ask a good enough question, and some well informed people are likely to show up! Once again I'm humbled by my lack of knowledge, but am happy to post at a place where there is such a deep well of knowledge to tap. Thanks!
Isn't that cool about this forum? I spilled coffee on my laptop keyboard and the enter key wouldn't work anymore. I thought I was in for a LARGE repair bill or a new computer since I'm pretty much a computer dummy. I posted about it just to see if there was any other thing I could do than lug around an external keyboard or pay through the nose and bingo! Someone linked me to a neat little program where I can "re-key" unused keys on my keyboard to do something else. I got my enter key back and it cost about an hour instead of hundreds of bucks. I'm a happy girl! Yep, this place is great.

~ Linda ~

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post #12 of 15 (permalink) Old 07-24-2007, 03:03 AM
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That's an awesome part of the forum, sharing knowledge.

Steve, don't sell yourself short, your electronic setup of the son of kahuna is a masterpeice.

Just to add to linda's post, Lotus seeds are the oldest viable seeds, thousands of years ago, a lotus set seed in an old chinese river. 3 thousand years later, the river is dry, and a scientist excavates an old lotus pod.
A few months of aging and preping, and there was a baby lotus.

-Devin-
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post #13 of 15 (permalink) Old 07-24-2007, 03:26 AM
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Steve, don't sell yourself short, your electronic setup of the son of kahuna is a masterpeice.
No kidding!


That's interesting about those lotus seeds, Dufus! Were they any different than the descended version of the species? Where can I read more about that? Interesting as all get out. I just love this kind of stuff.

Check this out ~ a story about a 2000 year old date palm seed that germinated. It happens to be of a species that went extinct in the Middle Ages! Here's another story with a lot more info ~ that one mentions lotus seeds from China sprouting, but they were only 1200 years old. ( Only 1200 years old. )

A quote from the second story I linked to:
Quote:
Lotus seeds about 1,200 years old have been sprouted in China, and after the Nazis bombed London's Natural History Museum in World War II and a lot of water was used to put out the fire, seeds about 500 years old also germinated.

~ Linda ~

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post #14 of 15 (permalink) Old 07-24-2007, 02:50 PM
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I don't remember where i read it, but if i can dig it up, i'll post the link.

-Devin-
Steve irwin- a father, a hero, a memory now. -We'll miss you mate
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post #15 of 15 (permalink) Old 07-24-2007, 06:39 PM
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Please do! I just LOVE reading about stuff like this. It's like making history literally come alive. Before hearing of the lotus you mentioned, the date palm and the 1200 year old lotus & 500 year old seeds in the above quote (isn't that a HOOT?! Water from the firefighting efforts made them sprout ~ still makes me giggle), the main "old seed" story I'd heard about was of the Anasazi beans.

~ Linda ~

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