Propagation 2011 - How much light is required?
Photosynthesis
To answer the question of 'what light to dahlias require to propagate?' I had to understand how plants grow. Photosynthesis is the way plants synthesise food directly from Carbon Dioxide - CO2 using energy from light. Water is also required, the whole cycle is called the Calvin Cycle - see diagram below.
Equation
The equation for photosynthesis is:
Carbon Dioxide + water + light energy ® carbohydrate + oxygen.
or in chemical symbols:
2n CO2 + 2n H2O + photons ® 2(CH2O)n + 2n O2
Chlorophyll
Plants absorb light primarily using the pigment chlorophyll. There are two structures which are relevant: chlorophyll a which is universal in occurrence, and chlorophyll b which is found in most plants. These have different peak absorbance frequencies which can be seen in the picture below. Using diethyl ether, chlorophyll a has absorbance peaks at 430nm and 662nm, whilst chlorophyll b has peaks at 453nm and 653nm.