Dustymac

Well, ever since I put the light on the other side, the leaves aren't growing straight up anymore. But 16 inches tall is OK, right?

Jim

mistergreen

Hi,
Just curious, what are some of the chemical make up of Allelochemicals. And if it's hard to do experiment with, how do we know it has any affect?

f1ea

I think there is another interesting component in the plant/algae 'equilibrium' in a natural or simulated environment.

So far 1) Alleopathy (in the form of chemicals released by the plants) and 2) nutrient competition (light, CO2, macros/micros) have been discussed here... But another component that might very well either assist or complement the Plant vs Algae battle in water systems is BACTERIAL COLONIZATION.

These bacteria could be 'hosted' by plants in a symbiotic relationship to help them outcompete algae, or they can be present in the water column, substrate etc... in this case, rather than wonder which and how much of a certain chemical a plants secretes that kills algae, we may be dealing with how much and which type of bacterial colony do we have in our tank that erradicates algae. It would also be easier to identify specific bacterial colonies in healthy water/tanks (with a microscope) rather than specific chemicals which may or may not harm algae and which may or may not have been released by plants...

I came accross this very interesting talk (link below), and if we humans live with an incredibly large number of bacteria performing protective and vital functions for us... why not plants as well??

http://www.ted.com/talks/bonnie_bass...mmunicate.html

Perhaps this is another way of plants beating out algae and another reason why sudden changes in conditions trigger algae: the bacterial colonies living on plants, the water column etc being much more primitive and simple organisms than plants/fish are much more susceptible to environmental conditions and therefore die easily, triggering algae outbreaks.

Not an easy subject anyway, but there went a few cents......

dwalstad

The list of about 30 specific inhibitory chemicals (e.g., nicotine, vitexin, etc) found in aquatic plants is in my book on pages 37-39.

Even though its very hard to do these experiments, a few investigators have done the job. I've discussed their work in my book. The hard part is showing that the other plant species didn't simply outcompete the other plant species for nutrients. The scientists doing these investigations were able to eliminate that variable and still show significant inhibition.

Allelopathy is real. Might (or might not be) relevant to aquariums. What intrigued me about allelopathy is the great effort that plants go to protect themselves with these chemicals. BTW, much of allelopathy is directed against herbivores. When you think of it, its pretty amazing that so few fish eat aquatic plants.

mistergreen

So in a healthy plant environment in the aquarium, what's the contributing factor that keeps the algae at bay? Is it the allelochemicals? Or many other factors as well.

I've always wondered why/how healthy plants can create an environment that keeps the algae spores from blooming.

Dustymac

interesting idea...but I would have to ask why there aren't similar bacteria which attack living underwater plants. Afterall, natural selection would suggest an equal opportunity for evolution. On the other hand, there certainly are plenty of bacteria in a fish tank. I see them in nearly every tank sample under the microscope.

f1ea

In the same vein: why would alleopathy work in a plant vs algae and not so much plant vs plant scenario? (perhaps minus some of the extra-invasive species).

Its not uncommon to see LOTS of plants coexisting in a small space with no algae (sure, there is nutrient competition and so on, but from a chemical point of view?).

Also, there is bacteria that 'attack' plants: cyanobacteria. But plants are much more complex than bacteria/algae, so it would seem reasonable that plants can form symbiotic relationships with bacteria to deter algae rather than algae to deter plants. Basicially, the most complex being has the advantage to form the symbiotic relationship.

Exactly, there is always bacteria present in water/soil; but the task would be to find which bacteria colony (and size) is present in tanks without algae that is not present in tanks with algae, and which plants are better at having such relationships. Maybe even someone could actually get to SEE a certain type of bacteria destroying algae cells in the way we've seen bacteria digesting, decomposing, nitrifying, attacking other cells etc....

I dont really have the experience/background to give 'solid' statements on these matters, but perhaps the more knowledgeable folks in here do or are able to deduct something more elaborate; so i guess nothing's wrong with a little bit of innocence....

Diana K

It has been shown that land plants do indeed have symbiotic relationships with bacteria and fungi. One of the most obvious is legumes (Peas, beans, alfalfa...) that have nodules on the roots. These nodules are Gram negative bacteria that have invaded the roots. They remove nitrogen from the atmosphere and make it available to the plants.
There are many other bacteria and fungi that are both positive and negative toward land plants, but not quite so many algae. It is possible to buy an innoculant for the soil to aid the plants in getting a good start by boosting the population of beneficial microorganisms.
http://en.wikipedia.org/wiki/Soil_inoculant

I would not be surprised that similar associations can be found in aquaria. I think this is part of what is going on when someone specifies that a certain fish or plant will thrive in a 'mature' tank, not a recently set up tank, even if it has a good nitrogen cycle going. It is all the 'other' microorganisms that are still sorting themselves out that must mean something to help or hinder fish and plants.

Land plants also display allelopathy. Some common examples: Look at how few plants grow under certain trees. Eucalyptus, Pine and Walnut are among the plants known to inhibit the growth of plants under their canopy. Even if plants do mange to grow under these trees the plants are often spindly, poor growing, and not dense, healthy plants.
On the other hand, there are plants that thrive under trees. Look at the Coast Redwood community on the west coast of North America. The plants that thrive here are specialists in their way, but the chemicals from the redwoods and other trees do not inhibit them.

dwalstad

I have hi-jacked this quote about allelopathy from another thread, because I think its a good addition to the allelopathy discussion.

Philosophos, I think you're on to something here. Rather than assuming that allelochemicals quickly disappear into the bulk water, I suspect they hang around long enough to inhibit algae. (Earlier I talked about how my Cryptocoryne cordata never has algae on its leaves, while other plant species easily succumb to algae.)

It is well known (by scientists) that the boundary layer (an unstirred region on leaf surface) is always present in aquatic plants. Water movement decreases the boundary layer, but it never becomes zero. Could released allelochemicals hang around within this layer long enough to impact algae?

As to waxy cuticles.... Deep-water rice actually brings air oxygen down to its root area on the outside of the plant. A waxy cuticle on leaf surface provides air layer whereby air can move downward to roots. The total volume of the air layers on both sides of the leaf is about 45% of the leaf blade itself.*

So these cuticles, waxes and boundary layers are micro-environments where allelochemicals could be concentrated enough to truly protect the plant.

*Raskin I and Kende H. 1983. How does deep water rice solve its aeration problem. Plant Physiology 72: 447-454.

mudboots

Nice indeed Dustymac.

Good thought provoking conversation. I have 0 water movement (this will change after I add a Koralia next week in the 125), and while I get lots of settling of "stuff" on leaves while the tanks heal from my inability to leave them alone, the only leaves with noticeable algae are my young anubias plants and some java "needle leaf". It's interesting that the regular Java fern is algae free while the needle leaf is not faring quite so well. Other than that it's just the driftwood (or deco regarding Abby's 10 gallon).