The vast majority of plant dry mass originates from carbon dioxide fixed from the atmosphere via photosynthesis, making this statement a matter of common scientific knowledge that requires no specific paper citation.
The claim that the vast majority of carbon in a plant originates from atmospheric CO2 rather than soil nutrients is a fundamental, textbook biological fact. Photosynthesis builds plant biomass primarily from air and water, with soil providing essential minerals and water rather than the bulk of the structural carbon. Pursuant to Step 0 instructions, trivially true everyday observations and foundational scientific definitions are classified as COMMON_KNOWLEDGE, requiring no papers and yielding empty index arrays.