MTTC Integrated Science (Secondary) (094) Practice Test

Gas exchange between inside tissues of a woody stem and the atmosphere is what lenticels enable. Lenticels are small, loosely structured openings in the outer bark that create intercellular air spaces, forming a diffusion pathway from the living tissues beneath the cork to the outside air. This allows oxygen to diffuse inward for cellular respiration and carbon dioxide to diffuse outward, especially important when the bark is thick andholds back direct gas movement. Water transport from roots uses the xylem, not these surface openings. Nutrient uptake from soil occurs mainly through roots and is transported through the phloem, not lenticels. Photosynthesis in bark cells is not the function of lenticels, which are about gas exchange rather than light capture.