Biology Do Now 3-11-19 Directions: Take out a sheet of notebook (Do Now sheet) and answer the questions.   What are the reactants in the photosynthetic reaction? What are the products in the photosynthetic reaction? What types of cells within the plant leaf carry out photosynthesis? What is the name of the structure in the leaf’s cells where photosynthesis takes place? How does the plant use sugars once they are made? (Two answers)

Biology Do Now 3-11-19 Key What are the reactants in the photosynthetic reaction? Carbon dioxide and liquid water What are the products in the photosynthetic reaction? Sugars and oxygen gas What types of cells within the plant leaf carry out photosynthesis? Palisade mesophyll and spongy mesophyll What is the name of the structure in the leaf’s cells where photosynthesis takes place? Chloroplast How does the plant use sugars once they are made? (Two answers) energy and structure

Objective Students will know how leaves turn air we breathe into food we eat by watching a video, completing a POGIL, engaging in a think-aloud, and reading/annotating an article about photosynthesis. Mastery level: 75% or better

Leaves: Form and structure

Leaves are like natural solar panels that can absorb solar energy. In solar panels, the solar energy is converted to electrical energy. However, in plant leaves, the solar energy is converted into chemical energy (sugars).

When leaves change colors… The green pigment, chlorophyll absorbs sunlight and water. When the days shorten, trees stop producing chlorophyll which exposes the other plant colors like yellow, orange and red. Plant veins close which traps sugars in the leaves creating bright fall colors.

The Plant Body: Leaves FUNCTION OF LEAVES Leaves are the solar energy and CO2 collectors of plants. In some plants, leaves have become adapted for specialized functions.

And so, on to leaves Leaves are the principle structure, produced on stems, where photosynthesis takes place.  Cacti are an exception.  The leaves are reduced to spines, and the thick green, fleshy stems are where photosynthesis takes place.

INTERNAL STRUCTURE OF LEAVES Each part of the leaf has an important job. chloroplasts Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Transports water and sugar to stem and roots Conserves water Photosynthesis Transports water and sugar to stem and roots Structures of the Leaf Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Structures of the Leaf Cuticle – the outermost layer of both the upper and lower surfaces of the leaf. It is clear and waxy to prevent against water loss. Epidermis – a layer of cells one cell thick that provides protection for the inner tissues. These cells are clear to allow light to reach the photosynthetic tissues. Mesophyll – between the epidermal layers. It contains palisade cells that are tall, tightly packed, and filled with chloroplasts for photosynthesis. It also has spongy cells which are irregularly shaped, have large air spaces between them, and fewer chloroplasts.

Structures of the Leaf Stomates – openings in the surface of the leaf and stems for gas exchange. The lower surface of a leaf usually has more. Water vapor also passes out through these holes. Guard cells – two of these special cells surround each stomate and regulate the opening and closing of the stomate. Veins – contain the vascular tissue that is continuous with that in the stem. Xylem carries water and minerals upward. Phloem carries dissolved food throughout the plant.

Typical Dicot Leaf Cross-Section Cuticle Epidermis Palisade Parenchyma Vascular bundles Guard Cells Spongy Parenchyma Stoma

Typical Monocot Leaf Cross-Section Bundle sheath cell Midvein Vein Epidermis Phloem Xylem Bulliform Cells Stoma

Function of the Leaf Photosynthesis Gaseous exchange take in O2 and release CO2 during respiration take in CO2 and release O2 during photosynthesis Water Vapour can be lost from the surface of the leaf in a process known as Transpiration.

GUARD CELLS AND PLANT HOMEOSTASIS Guard cells are kidney-shaped with thick inner walls and thin outer walls. When they become full of water (turgid) the unevenness of the walls causes them to bow outward and the stomate opens. When they lose water they become less turgid and the stomate closes. Guard cells gain and lose water by osmosis.

General overall reaction 6 CO2 + 6 H2O C6H12O6 + 6 O2 Carbon dioxide Water Carbohydrate Oxygen Photosynthetic organisms use solar energy to synthesize carbon compounds that cannot be formed without the input of energy. More specifically, light energy drives the synthesis of carbohydrates from carbon dioxide and water with the generation of oxygen.

Classwork Photosynthesis Worksheet Chromatography Article 1) Write 1 sentence that summarizes the article. 2) What is the main idea of the article? 3) What is chromatography? 4) What is chromatography used for? 5) Use your phone to define solvent and solvent front. 6) LOOK at the image on the back, SKETCH IT (on your paper) and EXPLAIN what it is showing. Answer all questions about photosynthesis on the worksheet. Please pardon the typos in the questions. #5) Why do most leaves appear green? #11) Name 3 sources of CO2.