Photosynthesis uses carbon and h20 as the reactants
For Absolute dating they assign a numerical date to each rock layer studied
For relative dating they go Through geological dating and stratigraphy processes. Also, they use Uranium Dating.
How day length affects crop production most plant donot grow when day length is less than 10 hours . Even if the temperature is kept within the optimum range _ For example in a climate _ controlled greenhouse _ most plant will just sit dormat until the magic 10 hours of light perday arrives