Theenergyandmassexchangesbetweenlivingorganismsandtheirenvironmentaretheprincipalphenomenathatdeterminetheexistenceoflifeonearth.Plants’abilitytotakeupwaterandnutrientsfromthesoil,fixcarbonfromtheatmosphereandusesolarenergytosynthetizesugarsthroughphotosyntheticactivityisakeyproces