Class Rules 1. Punctuality a. The last person to come into the class later than me will teach the class for 2 minutes on a selected topic by yours truly. b. Homework to be returned during the first Theory lesson of the week. 2. Cleanliness 3. Courtesy a. If you need to speak, raise your hands. b. If someone is speaking, open your ears, and not your mouth. 4. Consistency a. You must always have your notes with you. 5. Commitment a. If you are tasked to do something, I expect it to be done with all your effort. Topic Overview Transport in Plant Nutrition 6.1 Stem & Root Structure & Function 6.1.1 Vascular Bundle Structure & Function 6.1.2 Stem Internal Structure 6.1.3 Root Internal Structure 6.1.4 Leaf Internal Structure in Relation to Vascular Bundle Arrangements 6.2 Transport of Water & Minerals 6.3 Transports in Phloem 6.2.1 Water Potential 6.2.2 Overview of Water Movement 6.2.3 Water Movement in Roots 6.2.4 Mechanism of Water & Mineral Transport in Stems i) Root Pressure ii) Capillary Action iii) Transpiration & Transpiration Pull 6.2.5 Water Movement in Leaves 6.2.6 Factors Influencing Water Movement and Water Loss 6.2.7 Wilting 6.4 Water Relations & Leaf Adaptation 6.3.1 Pressure Flow Hypothesis 6.3.2 Evidence for Sucrose Translocation 6.4.1 Hydrophytic Leaves 6.4.2 Xerophytic Leaves Phloem Transport Xylem is UNIDIRECTIONAL. Phloem is BIDIRECTIONAL. Do you think transpiration pull is a model that can sufficiently explain phloem transport? What do you think is necessary in order for phloem sap to move? Phloem Transport Yes! You need a Driving Force! In order for a Driving Force to be established… You need to have some form of GRADIENT. Pressure Flow Hypothesis Difference in Hydrostatic Pressure 1) SUGAR SOURCE: Parts of plant where excess sugar being released or produced. 2) SUGAR SINKS: Parts of plant where sugar is consumed or stored. Sugar moves to SOURCE to SINK. Phloem Transport Phloem Loading 1. Sugar is first “loaded” from SUGAR SOURCE into Phloem by the Companion Cell. 2. Requires Energy. 3. Phloem Water Potential becomes MORE NEGATIVE 4. Water from Xylem enters Phloem by Osmosis. 5. High Hydrostatic Pressure in Phloem HIGH HYDROSTATIC PRESSURE Phloem Transport Phloem Unloading 1. Sugar is unloaded from Phloem into storage tissues 2. Requires Energy 3. Phloem Water Potential becomes LESS NEGATIVE 4. Water from Phloem returns to Xylem by Osmosis. 5. Low Hydrostatic Pressure in Phloem LOW HYDROSTATIC PRESSURE Pressure Flow Hypothesis Difference in Hydrostatic Pressure 1. Phloem Loading in Sugar Sources: High Hydrostatic Pressure 2. Phloem Unloading in Sugar Sinks: Low Hydrostatic Pressure http://highered.mcgrawhill.com/sites/9834092339/student_view0/ chapter38/animation__phloem_loading.html Evidence for Phloem Transport 1. Use of Aphids 2. Use of Radioactive Carbon Isotopes 3. Bark-Ringing Experiments Evidence for Phloem Transport 1. Use of Aphids Aphids extract phloem sap by inserting their proboscis into the phloem. 1. Anaesthetize aphids with CO2 while they are feeding. 2. Sever aphid body with laser. 3. Phloem sap flows out of severed proboscis by hydrostatic pressure. 4. Analyse phloem sap.. Voila! Sugars found! Evidence for Phloem Transport 2. Use of Radioactive Carbon Isotopes 1. Carbon-14, radioactive isotope of carbon. 2. Incorporated into CO2 . 3. Administered to plant. 4. Section plant and put on photographic plate. Evidence for Phloem Transport 3. Bark-Ringing Experiments Recall: Where is the position of the Phloem relative to the Xylem in a Dicot Stem? Pith Epidermis Cortex Vascular Bundle Topic Overview Transport in Plant Nutrition 6.1 Stem & Root Structure & Function 6.1.1 Vascular Bundle Structure & Function 6.1.2 Stem Internal Structure 6.1.3 Root Internal Structure 6.1.4 Leaf Internal Structure in Relation to Vascular Bundle Arrangements 6.2 Transport of Water & Minerals 6.3 Transports in Phloem 6.2.1 Water Potential 6.2.2 Overview of Water Movement 6.2.3 Water Movement in Roots 6.2.4 Mechanism of Water & Mineral Transport in Stems i) Root Pressure ii) Capillary Action iii) Transpiration & Transpiration Pull 6.2.5 Water Movement in Leaves 6.2.6 Factors Influencing Water Movement and Water Loss 6.2.7 Wilting 6.4 Water Relations & Leaf Adaptation 6.3.1 Pressure Flow Hypothesis 6.3.2 Evidence for Sucrose Translocation 6.4.1 Hydrophytic Leaves 6.4.2 Xerophytic Leaves Leaf Adaptations to Harsh Conditions “Normal” plants are known as Mesophytes. 1. Xerophytic adaptation 2. Hydrophytic adaptation 3. Halophytic adaptation Leaf Adaptations to Harsh Conditions 1. Xerophytic adaptation 1. Limit Water Loss 2. Water Storage 3. Water Acquisition Leaf Adaptations to Harsh Conditions 2. Hydrophytic adaptation 1. Gaseous Exchange 2. Floatation