In terms of organisms, photosynthesis occurs in autotrophes that contain the green pigment chlorophyll. This would include the entire plant kingdom, half of the Protista (the algae), & half the Moneran Kingdom (the blue-green algae).
A standard twin mattress is 39 by 75 inches. A king is 76 by 80 inches. This means that a headboard for a king bed is going to be about 76 inches or wider, plenty wide enough to go along the length of a twin bed. Headboards are often slightly wider than the bed for which they are made.
Putting an 80 inch king mattress on two regular 75 inch twin boxsprings is in fact 5 inches shorter than the king mattress leaving the 80 inch mattress hanging off the ends of twin boxspring by 5 inches leaving the mattress unsupported.