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.
We have two twin beds that we occasionally push together to make a king size for guests and wanted headboards that, when pushed together, would look like one board. This headboard is perfect for that. It looks great either as two twins or pushed together as a king and the color goes nicely with everything.