Effect of light intensity on the frequency of stomata

Question

According to this article, the frequency of stomata increases with an increase in the intensity of light. What I inferred from this is, since the rate of photosynthesis increases at higher light intensities, more C0₂ is is required and hence the frequency of stomatal openings increases.

I know that the Light Harvesting Complexes inside chloroplasts use light to release electrons, which are then subsequently used in photophosphorylation. If we compare the process with the photoelectric effect, we shouldn't see an effect of the intensity of light, but instead we should see changes for different frequencies(which we already do).

So how does the rate of photosynthesis increase with higher light intensities? Is the mechanism of light absorbtion by LHCs similar to that of a photoelectric cell?

Answer 1

You are misunderstanding photoelecric effect.

Intensity of light does not have effect on maximal kinetic energy of individual ejected electrons. Maximal kinetic energy of ejected electron is determined by energy it can get from single photon which is in turn determined by frequency of light.

However, intensity of light definitely does have effect on number of ejected electrons. More incident photons (higher intensity of light) result in more ejected electrons (and higher measured electric current).

In photosynthesis number of utilized photons is more important than their energy. Photon either does have enough energy for separating the electron (e.g. red or blue light) or it does not (e.g. infrared light). If a photon with energy higher than needed (e.g. blue light) is captured then the excess energy dissipates to heat.