transport in plants xylem: evapo-transpiration. objectives describe the structure of xylem vessels...

Download Transport in plants Xylem: Evapo-transpiration. Objectives Describe the structure of xylem vessels & sieve tubes. Describe the structure of xylem vessels

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Transport in plants Xylem: Evapo-transpiration Slide 2 Objectives Describe the structure of xylem vessels & sieve tubes. Describe the structure of xylem vessels & sieve tubes. Discuss how the structure of the xylem vessels suited for its function Discuss how the structure of the xylem vessels suited for its function Describe the process involved in transpiration. Describe the process involved in transpiration. Discuss the external factors that affect transpiration Discuss the external factors that affect transpiration Slide 3 Why do plants need a transport system? To transport food and water throughout the plant from roots to leaves at the top of the plant. To transport food and water throughout the plant from roots to leaves at the top of the plant. These substances are used by the plant to aid in photosynthesis. These substances are used by the plant to aid in photosynthesis. There are two structures used to transport material, the xylem vessels and phloem tubes. There are two structures used to transport material, the xylem vessels and phloem tubes. Vascular bundles are xylem and phloem tubes in close proximity to each other. Vascular bundles are xylem and phloem tubes in close proximity to each other. Slide 4 The position and orientation of vascular bundles vary throughout the plant. The position and orientation of vascular bundles vary throughout the plant. The phloem however is always found on the outer part of the bundle The phloem however is always found on the outer part of the bundle Slide 5 Xylem Xylem vessels transport water and dissolved minerals from the root to the shoot of plants. Xylem vessels transport water and dissolved minerals from the root to the shoot of plants. Slide 6 Xylem adaptations These are well adapted with: Long & Tubular cells Long & Tubular cells Hollow (no cell contents) Hollow (no cell contents) Thick bands of cellulose and lignin Thick bands of cellulose and lignin Water-resistant walls Water-resistant walls Slide 7 Direction of movement of substances in vascular tissue. Slide 8 Xylem tissue Slide 9 MONOCOTS Root pattern (xylem and phloem) ring Slide 10 DICOTS Stem pattern Ring- shaped xylem and phloem. LARGE CELLS ARE XYLEM SMALL CELLS ON OUTSIDE ARE PHLOEM Slide 11 DICOTS Root pattern (xylem and phloem) X-shape Slide 12 Mineral and water uptake in root *osmosis Slide 13 Slide 14 Casparian Strip The Casparian strip controls water movement into the vascular cylinder of the root. The Casparian strip controls water movement into the vascular cylinder of the root. Water cannot move between cells. It must move through the cells by osmosis. Why is this important? Water cannot move between cells. It must move through the cells by osmosis. Why is this important? Slide 15 Thinking question: What would happen in a root that had no Casparian strip? Why would this be a problem? What would happen in a root that had no Casparian strip? Why would this be a problem? Slide 16 Water movement up the xylem Step 1:Capillary action Step 1:Capillary action Cohesion and adhesion cause water to crawl up narrow tubes. The narrower the tube the higher the same mass of water can climb. Cohesion and adhesion cause water to crawl up narrow tubes. The narrower the tube the higher the same mass of water can climb. Maximum height: 32 feet. Maximum height: 32 feet. Slide 17 Capillary action Cohesion: polar water molecules tend to stick together with hydrogen bonds. Cohesion: polar water molecules tend to stick together with hydrogen bonds. Adhesion: water molecules tend to stick to polar surfaces. Adhesion: water molecules tend to stick to polar surfaces. Slide 18 Cohesion-tension theory Cohesion between water molecules creates a water chain effect. Cohesion between water molecules creates a water chain effect. As molecules are removed from the column by evaporation in the leaf, more are drawn up. As molecules are removed from the column by evaporation in the leaf, more are drawn up. Slide 19 Part 2: Root pressure There is a higher pressure in roots due to the higher conc. of water molecules being absorbed from soil. Water moves form area of high pressure (in roots) to low pressure (in leaves) Slide 20 Part 3: Transpiration pull due to evaporation Evaporation at the surface of the leaf keeps the water column moving. Evaporation at the surface of the leaf keeps the water column moving. This is the strongest force involved in transpiration. This is the strongest force involved in transpiration. Slide 21 Factors affecting transpiration rate Temperature: temp = TR Temperature: temp = TR Humidity: Humidity = TR Humidity: Humidity = TR Wind velocity: Wind velocity = TR Wind velocity: Wind velocity = TR Light intensity: affects stomatal opening Light intensity: affects stomatal opening Water content in soil : Less water in soil lead to less available for plants. The cellss get flaccid and in turn, plant wilts. Long term deprivation leads to death of plant. Water content in soil : Less water in soil lead to less available for plants. The cellss get flaccid and in turn, plant wilts. Long term deprivation leads to death of plant. Slide 22 Stomata control Guard cells around the stomata are sensitive to light, CO2, and water loss. Guard cells around the stomata are sensitive to light, CO2, and water loss. Cells expand in response to light and low CO2 levels, and collapse in response to water loss. Cells expand in response to light and low CO2 levels, and collapse in response to water loss. Slide 23 Stomata When stomata are open, evaporation draws water out of the leaf. Gas exchange can also occur to keep photosynthesis and respiration running. When stomata are open, evaporation draws water out of the leaf. Gas exchange can also occur to keep photosynthesis and respiration running. When stomata are closed, evaporation cannot occur, nor can gas exchange. What happens to photosynthesis and transpiration? When stomata are closed, evaporation cannot occur, nor can gas exchange. What happens to photosynthesis and transpiration?

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