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If you weigh a mature English oak, it might tip the scales at over fifteen tonnes — yet if you test the soil beneath its roots, virtually no soil mass has disappeared. Where did all that solid timber actually come from?
The answer is startling: almost every single kilogram of that wood was pulled directly out of thin air.
Can an invisible gas really be captured and woven into living wood? Let us trace how that physical transfer works.
The Gateway from Air to Leaf
In Earth system science, a flux is the rate at which carbon flows between stores over time. Photosynthesis is the primary biological flux transferring inorganic carbon from the atmosphere into the living biosphere.
Atmospheric carbon dioxide (extCO2) enters plant leaves through microscopic pores called stomata, moving passively along a concentration gradient from higher concentration in the open air to lower concentration inside the leaf's moist interior.
📊Interactive diagram
Once inside the leaf cells, how does that diffused gas transform into solid plant tissue?
The Chemical Fixation of Carbon
Inside leaf chloroplasts, the green pigment chlorophyll absorbs solar radiation. This light energy splits water molecules (extH2extO) drawn up through the roots, providing hydrogen and chemical energy to reduce and 'fix' the captured extCO2 into simple sugars.
This overall biochemical conversion is represented by the classic balanced equation:
6extCO2+6extH2extOextlightenergyextC6extH12extO6+6extO2
Plants do not keep this carbon as loose glucose. They assemble thousands of glucose units into giant structural polymers: cellulose for rigid cell walls and lignin for waterproof, dense wood.