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Photosynthesis Occurs in the Chloroplasts Leaves absorbs sunlight, CO2 and H2O Chloroplasts in cell Chloroplast Chloroplasts contain Chlorophyll To make ENERGY & GLUCOSE Structure of a Chloroplast (fluid) (a stack of thylakoids) What absorbs the light energy? • The chlorophyll is the pigment located in the chloroplast in the thylakoid membrane. • The pigments absorb the light energy from the sun, then the rest of photosynthesis takes place. The Leaf is… • the solar panel of the plant • arranged on the stem to maximize light absorption • used to capture light energy for photosynthesis • the chloroplasts are the site of photosynthesis So where does most photosynthesis take place in the leaf? Leaf Structure Drag and drop leaf quiz: http://tdflashzone.net23.net/index.php?p=2_60 Palisade Mesophyll Layer of a Leaf • Layer just beneath the epidermis • Tightly packed cells • Lots of chloroplasts • Most photosynthesis occurs here Spongy Mesophyll Layer of a Leaf • Layer beneath palisade • Loosely packed cells • Gas can move easily through air spaces • Some photosynthesis How Do Plants Get Carbon Dioxide? • Through the stomata (tiny openings) • Site of gas exchange •CO2 goes in •O2 goes out What Controls the Opening of the Stomata? • Guard cells: – Kidney-shaped cells around each stoma – Swollen guard cells = open stoma – Flaccid guard cells = closed stoma When are the Stomata Open? • During the day, when light is available for photosynthesis • Usually closed at night • Opening the stoma sacrifices water loss so they can’t stay open all the time Stomata! • Can you see the guard cells? • Why do you think they are mostly closed? • No photosynthesis happening at this time How Do Plants Get H2O from Roots to Leaves? • Water enters roots by osmosis. • Vascular plants transport water and minerals/nutrients through tissues called xylem (water transport) and phloem (food transport). • Once in the leaves, it can become a reactant in photosynthesis. Preventing Water Loss The Leaf’s Waxy Cuticle • A waxy covering that prevents dessication (drying out). • It is a plant adaptation to have a thick or thin cuticle • What type of plants need a thicker cuticle?
