What is the mechanism?

[Soilwork]

I was just sat here wondering why some plants in a hugely dense aquarium setting can still have perfectly healthy lower leaves that are almost shadowed in to complete darkness.

Then I thought that because the PAR is low at the site of these leaves that they can get by with less co2, less flow and less nutrients. But this would mean that the leaves have their won individual life cycle semi independent from the ‘main’ plant and when a leaf suffers a shortfall it falls off. I find this pretty remarkable if this is how it works, if all the leaves are working/sensing individually yet in unison for the greater good of the plant as a whole.

Any thoughts?

 

[dw1305]

Hi all,

Any thoughts?

It depends upon the nutrient status and type of plant.

If you have a shade adapted plant it won't necessarily absciss a leaf that is receiving PAR below compensation point. If you think of a tropical forest floor, plants are going to receive most of their light energy via transitory bright sun flecks, all of the rest of the time PAR will be below light compensation point.

If a plant is nutrient limited it will try to maximise the amount of light it can use, and then it will shed less photosynthetically efficient leaves.

There is good (scientific content) at <"Chapter 12 - Sunlight and plant production"> .

cheers Darrel

 

[Edvet]

Man Darrel you always have the good links

 

[dw1305]

Hi all,

Man Darrel you always have the good links

Serendipity, when the thread came up I was looking at that actual page with one of our students, because they've just competed a practical where they extract chlorophyll from shade and sun leaves of Common Nettle (Urtica dioica) and Common Lime (Tilia x europaea). They use a spectrophometer to measure absorbance (at 663 and 645nm) and then use one of the simultaneous equations to work out the chlorophyll a, chlorophyll b and total chlorophyll content. After that they perform some (appropriate) statistical analysis and decide if there is a difference, and why?

So it was a page that served both purposes.

cheers Darrel

 

[Edvet]

Lol

 

[Nelson]

Hi all, Serendipity, when the thread came up I was looking at that actual page with one of our students, because they've just competed a practical where they extract chlorophyll from shade and sun leaves of Common Nettle (Urtica dioica) and Common Lime (Tilia x europaea). They use a spectrophometer to measure absorbance (at 663 and 645nm) and then use one of the simultaneous equations to work out the chlorophyll a, chlorophyll b and total chlorophyll content. After that they perform some (appropriate) statistical analysis and decide if there is a difference, and why?

So it was a page that served both purposes.

cheers Darrel

I was just about to do that myself .

 

[AverageWhiteBloke]

Serendipity, when the thread came up I was looking at that actual page with one of our students, because they've just competed a practical where they extract chlorophyll from shade and sun leaves of Common Nettle (Urtica dioica) and Common Lime (Tilia x europaea). They use a spectrophometer to measure absorbance (at 663 and 645nm) and then use one of the simultaneous equations to work out the chlorophyll a, chlorophyll b and total chlorophyll content. After that they perform some (appropriate) statistical analysis and decide if there is a difference, and why?

So it was a page that served both purposes.

Just showing off now. I'll try and translate for the rest of us mere mortals. Not enough of a certain fert the plants will ditch leaves that get the least light. So the plant can focus its effort and what it does have left of the low nutrient on leaves that do *waits for Darrel to come back and say "not really, that all depends on...... "

As much as I try and simplify this hobby it just seems to get more complicated.

 

[Edvet]

just seems to get more complicated.

not always a bad thing, understanding the mechanisms made us be weary about to much light

 

[roadmaster]

I always thought CO2, or lack thereof down low in the tank(always wants to rise up/out), to be reason for plants to shed leaves in favor of those leaves higher up in the water column where CO2 is more plentiful.
Believe EI method of dosing would pretty much eliminate nutrient deficiency given the amount's and frequency of dosing.
Also,, I have seen houseplant's in window turn towards the glass where light is more available/ intense.
Can turn the plant away from the glass, and a few day's or week later,it has once again turned towards the glass.

 

[zozo]

In my outdoor aquarium stood a 180cm tall Lobelia cardinalis planted in the substrate.. The sideit was planted the submersed part was competely overgrowen with Potamogeton gayi, i didn't see any substrate for months, not from the side nor from the top.. After the summer i took all potamogeton out and every string wass in perfect health also the parts which where all the way down. What surpriced me the most was the perfectly healthy carpet of bright green Lobelia plantlets growing at submersed at the substrate level. It all grow under a dense layer of potamogetons from the mothers rootstock with a minimum of light. This can only mean the emersed mother was charing energy with her offspring..

First it looked like this, you see the Lobelia mothers base growing out the tank and the Potamogeton bellow it.

After taking all pondweed out, this is what Lobelia was growing submersed from her rootstock beneath all the pondweed.

 

[dw1305]

Hi all,

Not enough of a certain fert the plants will ditch leaves that get the least light. So the plant can focus its effort.....

That is it.

say "not really, that all depends on...... "

It doesn't work for shortages of non-mobile elements like iron (Fe).

I always thought CO2, or lack thereof down low in the tank(always wants to rise up/out), to be reason for plants to shed leaves in favor of those leaves higher up in the water column where CO2 is more plentiful.

That is the most likely element to be deficient.

A lot of "aquarium" plants will have the strategy of trying to become emersed as rapidly as possible (like Hygrophila), as soon as they do they will grow leaves with a different morphology and shed the submerged leaves.

The side it was planted the submersed part was competely overgrown with Potamogeton gayi,

Potamogeton spp. are obligate aquatic plants, and adapted to ambient CO2 levels, I would expect them to keep their leaves all the time there is sufficient PAR and nutrients.

This can only mean the emersed mother was charing energy with her offspring.......this is what Lobelia was growing submersed from her rootstock beneath all the pondweed.

Yes, the Lobelia plant will export nutrients to its over-wintering (perennating) stage. Lobelia cardinalis is native to <"N. America, all the way to Canada"> in the east, where you have a very cold winter. This means that the plant will lose its top growth every year to the frost. Often, in these circumstances the over-wintering stage will be an underground bulb or tuber, but Lobelia will overwinter via the basal rosette of evergreen foliage. The basal plants aren't really off-spring, they are the same plant as the flowering shoot.

cheers Darrel

 

[zozo]

Potamogeton spp. are obligate aquatic plants, and adapted to ambient CO2 levels, I would expect them to keep their leaves all the time there is sufficient PAR and nutrients.

Yes it absolutely did, the base substrate in this tank is a nutritious clay peat mix. And outdoor in the sun this plant is unstoppable, never seen it grow so much so fast in such density in such short time. And new shoots from the substrate completely covered and shaded was as healthy as everything above it.

I guess it's probably for all plants what you say about the Lobelia. If it originates from the same rootstock it is actualy one and the same plant and it shares everything mobile also with the most shaded parts all the way down. Compairing with how this potamogeton grows in the indoor tank, it sheds lower leaves, likely because the top doesn't get enough PAR to get the rootsystem running in a 100% capacity.. Matter of speaking..