d.  Nutrients (SPONCH)
	• 1.  Hydrogen from H2O • 2.  Carbon from CO2 • 3.  Nitrogen from N2 (NH3, NO3--, NO2-) • 4.  Oxygen from H2O and CO2 • 5.  Other essential nutrients (P, S, Mg, K, etc.) • e.  Anything else?