Mesophyll Architecture and Cell Exposure to Intercellular Air Space in Alpine, Desert, and Forest Species

Abstract

Internal leaf anatomy of 56 species in 21 families from alpine, forest, and desert habitats was examined for relationships between anatomical characteristics that might be linked functionally to photosynthesis. Leaf mesophyll architecture, particularly the amount of cell surface area exposed to intercellular spaces (Ames), expressed per unit leaf area (A), or Ames/A, has previously been associated with increased photosynthesis per unit leaf area. The numerical value of Ames/A is influenced by leaf anatomical characteristics that include leaf thickness; the amount of intercellular air space; and mesophyll cell size, shape, and density. The Ames/A values measured using digital image analysis of oblique and transverse sections of leaves ranged from 2 to 34. The most important single variable predicting Ames/A was not leaf thickness or cell dimensions but the percent of mesophyll volume occupied by intercellular air space, %IAS. In addition, the extent of contact between individual mesophyll cells appeared to...