Photosynthesis output

[Laserbeak]

I was wondering, what really is the output of plants as they are exposed to (sun)light?

To be simplistic, let's say something like corn in full summer noontime sun, how much of the sun's energy does it successfully capture per hour? What is the efficiency?

If anyone has information more specific to orchids, that would be great too.

[Pilot]

I have no idea. But I did grow up on a farm in Pennsylvania and have been in the field the day after a night storm, full noon sun as you say, and the very air around you crackles and hums as if life itself is in the air around you. Kinda freaky and amazing all at once.


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[shushu45]

[DavidCampen]

Measured in a bean plant, see Table II:
http://www.plantphysiol.org/content/46/1/1.full.pdf

Also:
The paper
"5.8 Photosynthetic Quantum Yield and Energy Conversion Efficiency
The theoretical minimum quantum requirement for photosynthesis is 8 quanta for each molecule of oxygen evolved (four quanta required by photosystem II and four by photosystem I). Measurements in algal cells and leaves under optimal conditions (e.g., low light) give quantum requirements of 8-10 photons per oxygen molecule released (see Emerson, 1958). These quantum yield measurements show that the quantum yields of photosystem II and photosystem I reaction centers under optimal conditions are near 100%."
and
"CO2 + 2H2O + Light Energy ______> [CH2O] + O2 + H2O

So, at 100% of theoretical efficiency, 8 quanta of light will fix the carbon in one molecule of carbon dioxide. Compare that with the bean plant measurements that found 9 - 14 quanta required to fix 1 molecule of CO2.

[Ray]

Originally Posted by DavidCampen

Measured in a bean plant, see Table II:
http://www.plantphysiol.org/content/46/1/1.full.pdf

David, surely that's a mistake in their abstract:

"The rate was measured as a function of the light intensity at steps of 12.5 nanometers which approximates the length of the leaflet used."

Those are awfully small leaves!!!

[DavidCampen]

Originally Posted by Ray

David, surely that's a mistake in their abstract:

"The rate was measured as a function of the light intensity at steps of 12.5 nanometers which approximates the length of the leaflet used."

Those are awfully small leaves!!!

Yes, whoever wrote the abstract mangled that. It should read something like

"The rate was measured as a function of the light intensity at steps of 12.5 nanometers which approximates the wavelength spread over the length of the leaflet used."

From page 2 of the text:
"Wave Length Range and Resolution.
The wave length limits of the flux incident on a leaf 125 mm long will be X + (D X 1/2) and X - (D X 1/2) where X = wave length at the center of the leaf, D = dispersion (Table I) and 1 = leaf length. For X = 500 nm
one edge is at 507.1 nm and the other at 492.9 nm. With a slit width of 25 mm, a magnification of 2.32, and a dispersion of 0.114 nm/mm, the range of the wave length falling at each point on the leaf will be 25.0 mm X 2.32 x 0.114 nm/mm = 6.6 nm"

[ALToronto]

There a discussion about this on the Slippertalk forum, where a member placed an orchid in a transparent enclosure with a CO2 meter inside and measured the reduction in CO2 levels under different types of lights

Light analysis - Slippertalk Orchid Forum- The best slipper orchid forum for paph, phrag and other lady slipper orchid discussion!.

[lazaah]

Photosynthetic evolution of C02 is routinely estimated using P.A.M. flurometry in the field, check it out on wikipedia

[Laserbeak]

Originally Posted by ALToronto

There a discussion about this on the Slippertalk forum, where a member placed an orchid in a transparent enclosure with a CO2 meter inside and measured the reduction in CO2 levels under different types of lights

Light analysis - Slippertalk Orchid Forum- The best slipper orchid forum for paph, phrag and other lady slipper orchid discussion!.

Great link thanks!

I need to study it more.