Effect of light intensity on photosynthesis

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The Effect of Wavelength on Photosynthesis Rate :: …

Johkan, M, K. Shoji, F. Goto, S. Hahida, and T. Yoshihara. 2012. “Effect of Green Light Wavelength and Intensity on Photomorphogenesis and Photosynthesis in Lactuca sativa,” Environmental and Experimental Botany 75:128-133.

Factors that influence the rate of photosynthesis.

McCree, K. J. 1972b. “Tests of Current Definitions of Photosynthetically Active Radiation Against Leaf Photosynthesis Data,” Agricultural and Forest Meteorology 10:443-453.

Above 700 nm, the photon energy is too low to activate the photosynthetic process via the chlorophylls and various cartenoids. However, the phytochrome photopigment, which is responsible for stem elongation, leaf expansion, shade avoidance, neighbor perception, seed germination, and flower induction, has two isoforms called Pr and Pfr. In its ground state Pr, phytochrome has a spectral absorbance peak of 660 nm. When it absorbs a red photon, it converts to its Pfr state, which has a spectral absorbance peak of 730 nm. When the phytochrome molecule absorbs a far-red photon, it converts back to its Pr state, and in doing so triggers a physiological change in the plant.


Why the rate of Photosynthesis is higher in red light …


It may seem surprising but there are almost no journal articles by chemistry researchers on the effect of surface area on reaction rate - in industry or academia. Those that do relate to the area of catalysts rather than the main reactants (but that does suggest another EEI topic). The most recent paper as a stimulus for a high school chemistry EEI is one by industrial chemists Glenn Damon and Ray Cross from the Michigan College of Mining and Technology, Houghton, Michigan published in journal V28 (2) in February 1936. They reacted sulfuric acid with small squares of copper placed 2 cm under the liquid surface. However, to manipulate the surface area variable they varied the surface area of the solution exposed to the atmosphere. You could prepare a small circular piece of polystyrene foam (with a hole cut in the middle) and float it on the surface of the acid. This will give limited access of oxygen to the solution and hence limit the corrosion of the copper. It is a neat experiment and may give you a few ideas. to download it.

Factors Affecting The Rate Of Photosynthesis - …


You may have also tried this using marble chips and calcium carbonate powder. But how to measure the surface area? My suggestion is to get some marble tiles from a tile shop and cut them into strips with a masonry blade on an angle grinder. If you have five strips you can break one in half, one in quarters and so on. Using a Vernier calliper it will be easy to measure surface area. The method id quite straightforward after that. Nevertheless, give some thought to how you will control temperature, and how much acid you will need, and what concentration so that it is not the limiting reagent. Lastly, what will you measure for reaction rate: time taken for the chips to dissolve, or a flask on a balance with recordings taken every minute...and so on. A great technique for an EEI would be to pour off the acid after a given time and titrate it with standardized NaOH solution to see how much acid (and hence marble) was used.

Investigation into the Factors Affecting The Rate Of Photosynthesis

But how to get samples of these gases? You may have cylinders but you could produce H2 and CO2 by reaction (or let some dry ice sublimate); let some liquid nitrogen evaporate (or remove oxygen from air). And why not propane (BBQ gas) or butane (cigarette lighter fluid)? Remember that balloon gas is not just helium - it has 3% air mixed in with it. The main point is that the law holds for ideal gases but at atmospheric pressure and room temperature they won't be that ideal. And is the deviation from ideality dependent on the molar mass of the gas, or whether it is polar or non-polar, and where on earth do you get a polar gas from (HCl is too dangerous)? What range of temperatures will you use (consider liquid nitrogen, dry ice). What value will they give you for absolute zero when the V/T graph is extrapolated? How do you draw the line of best fit (is least-squares the best, does it give you the most accurate value for absolute zero?). And what is the volume of the gas in the apparatus? And what is the best way to measure temperature (of the gas as in the diagram, or of the water surrounding it)?