142M471B3J Carbon Dioxide Journal Article Research Support, Non-U.S. Gov't Anatomy Conifer LES LMA N762921K75 Nitrogen Potassium RWP5GA015D S c/S cell wall thickness chloroplast area exposed to intercellular airspace conifers gm gymnosperm gymnosperms leaf anatomy leaf economic spectrum leaf gas exchange leaf internal CO2 transfer leaf nutrient content mesophyll conductance nitrogen photosynthesis. photosynthetic capacity photosynthetic limitation