BIOSCI 152 1st Edition Lecture 16Plant Form and Function II Leaf anatomy and photosynthesis Learning Objectives: After suitable revision, you should be able to –  Describe a leaf cross section and know the types of cells and where photosynthesis is carried out  Describe the basic structural components of a chloroplast  Name the major pigments plants use to absorb light for photosynthesis  Explain how pigment absorption spectra relate to photosynthesis action spectra  Name the substrates and products of photosynthesis  Explain how the light and dark reactions of photosynthesis interact  Name the cycle for CO2 fixation and the first enzyme catalyzing CO2 fixation  Explain the advantages and benefits of C4 and CAM photosynthesis for plants and the basic differences between C4, CAM and C3 photosynthesis Vocabulary Leaf Chromatography Epidermis Light reactions Cuticle Light-independent (dark) reactions Mesophyll Calvin (C3) cycle Palisade mesophyll ATP Spongy mesophyll NADPH Vascular tissue Organic C Stomata (stoma) Carbon dioxide Gas exchange Chemical energy Guard cells Electron transport Chloroplast 3-phosphoglycerate Thylakoid membrane Starch Grana (granum)Sucrose Stroma Cellulose Pigment C4 metabolism Absorption spectrum Crassulacean acid metabolism Chlorophyll (CAM) Carotenoid Plasmodesmata Absorption spectrum Water use efficiency Action spectrum Climate change Plant Form and Function II Leaf anatomy and photosynthesis Learning Objectives: After suitable revision, you should be able to –  Describe a leaf cross section and know the types of cells and where photosynthesis is carried out  Describe the basic structural components of a chloroplast  Name the major pigments plants use to absorb light for photosynthesis  Explain how pigment absorption spectra relate to photosynthesis action spectra  Name the substrates and products of photosynthesis  Explain how the light and dark reactions of photosynthesis interact  Name the cycle for CO2 fixation and the first enzyme catalyzing CO2 fixation  Explain the advantages and benefits of C4 and CAM photosynthesis for plants and the basic differences between C4, CAM and C3 photosynthesis Vocabulary Leaf Chromatography Epidermis Light reactions Cuticle Light-independent (dark) reactions Mesophyll Calvin (C3) cycle Palisade mesophyll ATP Spongy mesophyll NADPH Vascular tissueOrganic C Stomata (stoma) Carbon dioxide Gas exchange Chemical energy Guard cells Electron transport Chloroplast 3-phosphoglycerate Thylakoid membrane Starch Grana (granum) Sucrose Stroma Cellulose Pigment C4 metabolism Absorption spectrum Crassulacean acid metabolism Chlorophyll (CAM) Carotenoid Plasmodesmata Absorption spectrum Water use efficiency Action spectrum Climate changeLeaf structure and tissue organization Fig. 24.12 • Epidermis • Mesophyll (meso – middle, phyll- leaf) • Palisade mesophyll – top • Spongy mesophyll - bottom • Vascular tissue Epidermis and Stomata • Cuticle • Stomata (singl. Stoma) Stomata Fig. 25.13 • CO2 enters, H2O and O2 leave during the day (photosynthesis and transpiration) • O2 enters, CO2 leaves during the night (Respiration) • Guard cells regulate gas and water vapor movement by opening and closing stomaLeaf structure and tissue organization Fig. 24.12 • Epidermis• Mesophyll (meso – middle, phyll- leaf) • Palisade mesophyll – top • Spongy mesophyll - bottom • Vascular tissue Epidermis and Stomata • Cuticle • Stomata (singl. Stoma) Stomata Fig. 25.13 • CO2 enters, H2O and O2 leave during the day (photosynthesis and transpiration) • O2 enters, CO2 leaves during the night (Respiration) • Guard cells regulate gas and water vapor movement by opening and closing stomaMesophyll Tissue Palisade layer – main site of photosynthesis Spongy mesophyll – loose packing of cells facilitates gas diffusion. Some photosynthesis occurs hereVascular Tissue • Continuous with stem (and roots) • Xylem + Phloem • Structural support and transport Leaf structure and photosynthesis Typical leaf palisade cell contains 30 – 40 chloroplasts • Cell is 30-40 um diam. = 0.00004 m • Chloroplast is 2-10 um diam = 0.000002 m • Chloroplast has circular genome – endosymbiotic origin • Outer and inner membranes • Stroma and thylakoid membranes  Thylakoid membranes - function in the light reactions (photosynthesis) - converting light energy to chemical energy  Thylakoids stacks (grana/granum) contain chlorophyll and accessory pigments that absorb light  Stroma - functions in the light- independent reactions (dark reactions), which fix carbon dioxide and H2O into sugars – (Calvin Cycle)Mesophyll Tissue Palisade layer – main site of photosynthesis Spongy mesophyll – loose packing of cells facilitates gas diffusion. Some photosynthesis occurs hereVascular Tissue • Continuous with stem (and roots) • Xylem + Phloem • Structural support and transport Leaf structure and photosynthesis Typical leaf palisade cell contains 30 – 40 chloroplasts • Cell is 30-40 um diam. = 0.00004 m • Chloroplast is 2-10 um diam = 0.000002 m • Chloroplast has circular genome – endosymbiotic origin • Outer and inner membranes • Stroma and thylakoid membranes  Thylakoid membranes - function in the light reactions (photosynthesis) - converting light energy to chemical energy  Thylakoids stacks (grana/granum) contain chlorophyll and accessory pigments that absorb light  Stroma - functions in the light- independent reactions (dark reactions), which fix carbon dioxide and H2O into sugars – (Calvin Cycle)Light spectrum (wavelength - energy) Fig. 6.16 • Why are leaves Green? • Chloroplasts reflect green, absorb red and blue light (source of light for photosynthesis) White light composed of spectrum of (rainbow) colors • Color observed = color reflected, not absorbed •Chlorophyll molecules are main light harvesting pigments •Fig. 6.18 Absorption and Action spectra (graph plotting pigment absorption or