I just want to throw a topic for discussion.
I have limited knowledge about plant biology. I would like to seek opinions from you guys for my views below.
Increase in temperature will increase the metabolism rate(enzyms activity, etc.) and respiration (consumption of carbohydrate and giving out CO2) in plants. This will drive up plants demand for C and energy and other nutrients. It will also reduce the stored carbohydrate in plants.
Increase in temperature also the photosynthetic rate in plants up to a certain point (at fixed light and CO2 level). The maximum point is limited by the photorespiration. Photo respiration will increase at an increasing rate with temperature. The gross photosynthesis rate is increasing at a decreasing rate with temperature. There will be a optimal temperature wher the net photosythesis (gross photosynthesis - photorespiration) will be at maximum. Beyond that temperature, the increase photorespiration rate will exceed the increase in photosynthetic rate and the net rate of photosynthesis will reduce.
The problem will set in when the temperature rises beyond the optimal temperature. The net photosynthesis will reduce while the metabolism/respiration will continue to increase and demanding more C and energy. This is happen when we have high temperature but low light and CO2.
To overcome the problem at higher tempature, we can increase the light and CO2 level. This way we can raise the optimal temperature. And the increase the photosythetic rate will help to overcome the demand from the increase in metabolism/respiration.
What is your take on this?
BC
I know that prolonged heat stress will also cause denaturing of proteins within plants (another way to kill plants), not only an imbalance in metabolism. Plants deal with denaturing by synthesising heat-shock proteins (HSP) hence, it is my opinion that chemical energy maybe diverted to its synthesis instead of growth.
Geoffrey, does this denaturing of protein occur within the temperature range of our aquariums?
BC
In the literatures I read, they don't exactly tell you at what temp denaturing starts and it's plant dependent. However they do say that when plants are exposed to temp at 38~40Deg for a few minutes, the synthesis of normal proteins slowed dramatically and the synthesis of HSP increases significantly.
The question I like answered is if it takes only a few minutes at 38 Deg for a plant to synthesis HSP at the expense of growth to protect itself from heat stress, would the 28~31Deg over a prolonged period actually have the same effect?
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Does that literature tells you that the temperature was at 38~40 deg when it happen or did the temperature had started from somewhere lower?
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I am guessing that heat shock may not be as significant as the energy balance in the typical temperature range of our tank. The temperature we operate our tank in may be beyond the optimal temperature for some plants.
I understand that there is 3 main components in the energy balance equation.
1. Photosynthesis
2. Photorespiration
3. Respiration
Net photosynthesis = photosynthesis - photorespiration - respiration
Both photorespiration and respiration will increase exponentially with temperature.
Photosynthesis (at a fix light/CO2 level) will increase with temperature but the rate of increase will lower with temperature.
Here is one chart I got from the net.
There will be a point where the increase of photosythesis with temperature is equal to the increase of respiration/photorespiration. That is the optimal temperature. Beyond that the increase of photosynthesis with temperature will be lower than the increase of respiration/photorespiration. The net photosynthesis rate will reduce. Finally there will be a point (Tmax) where respiration/photorespiration exceeds the photosythesis. That will be when the plant start to die.
When we raise the light and CO2, the photosynthesis rate will increase while reducing photorespiration. That means for a specific temperature the net photosynthesis will be greater. Therefore, this will push the envelope higher and we have a higher optimal temperature and maximum temperature.
BC
No, those books I read are simpler ones that do not say but I found in the website, super chimmer that I don't understand a thing. Some kind of experimental procotol where temp are raise slowly, certain conditional setup, here and there, this and that...and then that and this is measured...----------------
On 10/16/2003 1:06:37 AM
Does that literature tells you that the temperature was at 38~40 deg when it happen or did the temperature had started from somewhere lower?
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I tend to agree with BC that heat-stress is less likely in our tanks but could it be possible that plants may be forgoing some growth for some HSP for protection against some denaturing at those temp range of 29~31 that we are experiencing.
BTW, high temp also causes leaky cell membranes, lipids. Affects ions and solute transporting.
bclee,
Those are theories though every things we do we wish to have figures as a medium to represent the findings.
Plants' servivor, growth and being healthy require a complete set of equations. Some camps said there are no fixed formulae, to some extend yes. However, there are certain perimeters we can stick to for a good tank.
Lately, I had been thinking why vetarans say matured tanks do wonders to plants, they could not explain that fully too. I am close to conclusion that bio-modified chemicals have alot to do with well being of plants. Much more important than all have been dicussed here about light, CO2, pure chemical fertlisers, etc.
I have now a very forgiving and relatively successful planted tank that I beleive is coming from the matured gravel that I artficially boosted. I beleive the bio activities there did many wonders with the fish wastes to serve the plants.
Regards,
Freddy Chng
www.killies.com
don knw wat u guys talking about. totally confuse....
[]
Understanding the science behind certain phenomena definitely will help to push the hobby further. Anyway, you do not have to fully understand the science behind it to make things work.
I am always inquisitive on all the things I see.
I have seen many tanks with very low light and people are able keep many plants that I struggle to keep alive under low light. (I doubt having a mature substrate will help this.) The only difference I find is the temperature. Their tanks are running at 23-24°C while mine is consistantly at >27°C. That spur me to find out whether temperature is a critical factor for low light tanks.
I hope that hobbyist who have experience or knowledge on this can share so that all can benefit.
BC
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On 10/17/2003 11:12:21 AM
don knw wat u guys talking about. totally confuse....
[
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To put it very simply...
I am trying to say low temperature is important for low light/non-CO2 tanks. Some plants can run into problems in low light and high temperature. High temperature push the plant to consume more energy. But low light and CO2 do not give the plants enough energy to cope with that, so some plants die.
If you are able to lower the temperature, you might be able to keep more plant varieties in low light condition. If you cannot keep temperature down, you will need more light/CO2 for the plants to cope with the energy demand from high temperature.
... better?
BC
bc, now i understand better liao. u really are somebody that knw and contribute alot to this hobby in my opinion.
thanks and hip hip huray!
bc, what kind of plants do you have in your tank
do you have any experience with taiwan moss at a temp >27
please share
thanks
Currently, I have Bacopa caroliana, Lobelia cardinalis, Barclaya longifolia, Hydrocotyle leucocephala, Cryptocoryne undulata, Marsilea sp., Elatine triandra, Eleocharis parvulus, Vallisneria americana and Tonina sp from Balem.
I have no experience with mosses.
BC
I managed to discuss this topic with Ole at the Tropica booth at the Aquarama.
Basically, he agreed that plant die at high temperature due to enzymes working faster at high temperatures. This "burns" the plant up as the plant cannot photosynthesis enough to meet what is consumed. Plants usually die off very fast (could be overnight) this way.
More CO2 and light can help, but there is still a limit how much more photosynthesis a plant can produce.
BC
Which is why global warming would eventually kill the earth. No plants...no oxygen...no life. []
Plant Physiology by Taiz and Zeiger
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