2.42B: Understand How the Structure of the Leaf is Adapted for Gas Exchange

STRUCTURE OF PLANT LEAF:

                                 

Diagram showing Cross-section of Plant Leaf

ADAPTATIONS FOR GAS EXCHANGE:

FEATURE	ADAPTATION
STOMATA	Opens to allow the diffusion of Carbon dioxide into the leaf for Photosynthesis, and the diffusion of waste products of Oxygen and Water vapour out of the leaf - gas exchange
GUARD CELLS AROUND STOMATA	Controls the opening and closing of Stomata depending on the time of day to enable gas exchange - e.g, Guard cells become turgid during daytime to open Stomata and allow diffusion of Carbon Dioxide into the leaf for Photosynthesis (due to presence of sunlight)
THIN	Minimises the diffusion length of Carbon Dioxide into the leaf (for Photosynthesis), and Oxygen and Water (waste product of Photosynthesis) out of the leaf, therefore increasing the rate of gas exchange
FLATTENED SHAPE	Larger surface area to volume ratio increases the rate of absorption of sunlight and Carbon Dioxide for use in Photosynthesis, therefore increasing rate of gas exchange
INTERNAL AIR SPACES IN SPONGY MESOPHYL	Larger internal surface area to volume ratio for absorption of Carbon Dioxide into the leaf (for Photosynthesis), therefore increasing the rate of gas exchange