Specialized Plant Cells: Transport in Leaves 9 Bio

Leaf Structure- Overview Leaf structure is arranged in layers: 1. Upper epidermis Waxy cuticle prevents water loss 2. Pallisade layer Chloroplasts – photosynthesis (glucose production) 3. Spongy pallisade layer Storage of H2O, CO2 and O2 4. Lower epidermis Stomata and guard cells regulate the passage of water vapor( transpiration), intake of CO2, output of O2

Palisade Mesophyll Layer Contains chloroplasts: Outer membrane Granum- stack of thylakoids Thylakoids- contain chlorophyll, catch photons of light photosynthesis glucose Stroma- fluid filled space

Spongy Mesophyll Layer Open space to store gases ( CO2 and O2) and H2O molecules for exchange in atmosphere CO2 needed for photosynthesis O2- by-product of photosynthesis H2O- transpiration

Lower Epidermis Has guard cells surrounding stomata Stomate (singular) Opening and closing of stomata regulated by plant hormone abscisic acid Abscisic acid present: K+ leaves, H2O leaves, stomata close Abscisic acid absent: K+ stays, H2O stays, stomata open

Regulation of Transport Lower Epidermis: Takes in CO2 for photosynthesis Releases O2 from photosynthesis Releases H2O (Transpiration) Why would stomata remain closed in arid conditions? When might plants lose the most H2O? When might plants produce a high level of O2? When might plants need a greater amount of CO2?