Photosynthesis and Leaf Structure

Parts of a Plant Leaf: where photosynthesis occurs Stem: support system to hold plant upright Roots: takes in water from the soil

Why are leaves GREEN?

Photosynthesis occurs in the Leaf Leaf has a large surface: lots of chloroplasts & chlorophyll Can capture a lot of sunlight

Gas Exchange Happens at the Leaf Stomates: holes in the bottom of the leaf that allow Carbon Dioxide (CO2) in and Oxygen (O2) out Stomates

Water loss Happens at the Leaf Transpiration: Plant “sweat”, leaves plants through their stomates Stomates

Guard Cells control the Stomates Each stomate is surrounded by 2 guard cells Guard Cells: control if the hole is open or closed Can prevent water loss! Guard Cells

Guard Cells Guard Against water Loss Closed Stomate - Water is not lost Open Stomate - Allows water out & gases in and out

stomate guard cells epithelial cells

Challenge! On notebook paper In some land plants, guard cells are found only on the lower surfaces of the leaves. In some water plants, guard cells are found only on the upper surfaces of the leaves. Explain how guard cells in both land and water plants help maintain homeostasis. In your answer: • identify one function regulated (controlled) by the guard cells in leaves • explain how guard cells carry out this function • give one possible advantage of the position of the guard cells on the leaves of land plants

Challenge! • identify one function regulated (controlled) by the guard cells in leaves • explain how guard cells carry out this function • give one possible advantage of the position of the guard cells on the leaves of land plants