Presentation on theme: "Leaf Anatomy Objectives:"— Presentation transcript:
1 Leaf Anatomy Objectives: 1. Identify Internal and External Leaf Anatomy2. Learn the function of these structures3. Write the equation for photosynthesis4. Make quality wet-mount slides to observe these structures.
2 The Leaf – External Anatomy VeinBlade,(Lamina)MidribStalk/petiole
3 The Leaf – Cross-section VeinLaminaMidribMidribExtension of the stalk into the leafVeinBranch-off from the midribLaminaThe blade of the leafStalkAttaches the leaf to the stem
5 Waxy Cuticle & Epidermis The waxy cuticle is a thin layer atop the epidermis.Its function is to reduce the water lost from the leaf.In arid conditions this cuticle layer can be quite thick.Epidermis cells contain no chloroplasts – not true of the stoma cells.They form layers on the upper and lower surfaces of the leaf.Their function is to prevent water getting out and stopping unwanted substances/organisms getting in.
6 Palisade Mesophyll Layer The palisade mesophyll layer is where most of the photosynthesis occurs in the leaf.Palisade mesophyll layerThe palisade cells contain a lot of chloroplasts to help them perform this photosynthesis.The palisade cells are closely packed together to maximize light absorption.In the leaf cross-section we can see the palisade cells are only found in the upper part of the leaf.
7 Spongy Mesophyll Layer The cells in the spongy mesophyll layer are not as closely packed as the cells in the palisade mesophyll layer.This creates air spaces inside the leaf to enable gases to move in and out.Spongy mesophyll layerThere are not as many chloroplasts in the spongy mesophyll cells as there are in the palisade mesophyll cells – but photosynthesis still occurs in the spongy mesophyll layer.
8 Stomata There are holes found in leaves called stoma. These holes allows gases to diffuse in and out of the leaves.The stoma are formed by two highly specialized epidermis cells.These cells, called guard cells, are the only epidermis cells that contain chloroplasts.The stoma open and close depending upon the requirements of the plant.It is through these stoma that water leaves the leaf, the process that powers transpiration.Stomata
9 Stomata Stomata open Stomata closed During photosynthesis carbon dioxide diffuses in and oxygen diffuses outWhen the stomata are closed,often at night or in a humid environment, this stops gases diffusing in and out of the leaf
10 Key Words Waxy cuticle Waterproof layer atop the epidermis Stoma Pores that allow gaseous exchangeFound in the spongy mesophyll layer, enable gases to reach the leaf cellsAir spacesOne-cell thick outer layer of cells that prevent water loss from the leafEpidermisPalisade mesophyll cellContain numerous chloroplasts and are densely packedLoosely packed cells that do not contain as many chloroplasts as palisade cellsSpongy mesophyll cell
11 PhotosynthesisChloroplasts are organelles of plant cells that contain a chlorophyll which absorbs light energy and this energy is then used to make food.The raw materials of photosynthesis are carbon dioxide and water. The waste product of this reaction is oxygen.The carbon dioxide required is absorbed through the stoma in the leaves – this is how the oxygen is also removed.The water required is absorbed by the roots.The word equation for this reaction is...The chemical equation for this reaction is...6H2O + 6CO2 C6H12O6 + 6O2
12 Review: Leaf Anatomy 1. _____ Vein 2. ______ Lamina 3. _______ Midrib Extension of the stalk into the leafVeinThe blade of the leafLaminaAttaches the leaf to the stemStalkBranch-off from the midrib
14 Pores that allow gaseous exchange Waterproof layer atop the epidermis Review: FunctionPores that allow gaseous exchangeWaxy cuticleFound in the spongy mesophyll layer, enable gases to reach the leaf cellsStomaWaterproof layer atop the epidermisAir spaces
15 Palisade mesophyll cell Review: FunctionLoosely packed cells that do not contain as many chloroplasts as palisade cellsEpidermisOne-cell thick outer layer of cells that prevent water loss from the leafPalisade mesophyll cellContain numerous chloroplasts and are densely packed, where most of the photosynthesis occursSpongy mesophyll cell
16 Review: Insert the Missing Words Chloroplasts are __________ of plant cells that contain a green substance called __________.Scientists believe chlorophyll absorbs _____ energy and this energy is then used to make _____.The raw materials of photosynthesis are carbon dioxide and _____. This waste product of this reaction is _______.The carbon dioxide required is absorbed through the ______ in the leaves – this is how the oxygen is also removed.The water required is absorbed by the _____.organelleschlorophylllightsugarwateroxygenstomarootsroots organelles light sugarwater chlorophyll oxygen stoma
17 Review: Short Questions - Photosynthesis 1. Which organelles in plant cells contain a green substance called chlorophyll?2. Which two raw materials are required by green plants for photosynthesis?3. What is the waste product of photosynthesis?4. Where does this waste product leave the plant?5. What process uses this waste product to enable green plants, and us, to release energy from their food?ChloroplastsWater and carbon dioxideOxygenThrough the stomata (stoma – pl.)Respiration
18 Review: Short Questions – Plant Nutrition 1. What do we call the process whereby green plants make glucose using light energy and the raw materials carbon dioxide and water?2. During the night many green plants perform another process whereby they release the energy from their food they have made. What do we call this process?3. The sugar glucose, the product of photosynthesis, is changed to starch when it is being stored by the plant. Why?4. What is the chemical formula of glucose?PhotosynthesisRespirationGlucose is soluble in water, starch is insoluble in water. By storing the food starch it means it is easier for the plant to keep the food in the required placeC6H12O6
19 Exercise 10: Short Questions – Plant Nutrition 1. What is the word equation for photosynthesis?2. What is the chemical equation for photosynthesis?3. Name the arrowed organelle.4. Which substance does this organelle contain that allows green plants to absorb the Sun’s light energy for the process of photosynthesis?6H2O + 6CO2 C6H12O6 + 6O2ChloroplastChlorophyll
20 Exercise 2: Label the Parts of a Plant 1. _______Flower2. _______Leaves3. _____Stem4. ______Roots
21 Exercise 3: Label the Parts of a Plant LeafRootsStemFlower