2Transport SystemThe vascular tissues found in plants are the xylem and the phloemThe function of the xylem is to transport water and mineral saltsThe function of the phloem is to transport food materials: mainly sugars and amino acids
3Where Are The Xylem And Pholem? In the Leafmid-ribveinphloemxylem
4Where Are The Xylem And Pholem? In the StemPhloemXylem(note thickened cross walls)Cross-section of stemHigh magnification of a single vascular bundle
5Transport Of Water And Mineral Salts and is lost to the surroundings by the process called transpirationis used in respiration and other cellular activitiestransported up the stem by xylem vesselsWater is absorbed from surrounding soil by root hairs
6Transport Of Water And Mineral Salts The Uptake of WaterUp xylem vessels to plantWater from soilabsorbed into root hair cellacross cortex cellsacross phloeminto xylem vessels
7Transport Of Water And Mineral Salts The Uptake of Mineral SaltsPlants absorb mineral salts in the form of ions dissolved in soil water through the root hairs. This may take place via diffusion.When there is a lower concentration of ions in the soil than the root hairs, ions do not diffuse into the root hairs.It involves the movement of ions against a concentration gradient, and to do this root hairs need energy. This process is called active transport.
8Transport Of Water And Mineral Salts Adaptations of the Root Hair CellThe root hair extends from the root cell. It is long and narrow. This provides a larger surface area to volume ratio for water and nutrients to be absorbed.Soil particlesWater and mineral saltsThe root hair cell is living. It carries out respiration to replace energy that is required for active transport.The cell sap in the root hair cell is of lower water potential than the soil solution. This allows water to enter the root hair by osmosis.
9Transport Of Water And Mineral Salts Transport in the XylemThere are 3 forces that move the water upwards in the xylem:Root pressure - a force that pushes water up the xylem (produced by the continuous movement of water through the root cells.Capillary action - a force that pushes water up the narrow xylem vessels.Transpirational pull - a force that pulls water up the xylem (produced by evaporation of water from the leaves).
10Transpiration Pull In Plants Transpiration is the loss of water in the form of water vapour from the leaves, especially through the stomata, as a consequence of gaseous exchangeThe importance of transpiration:Transpiration pull which is a main factor in ‘lifting’ and sustaining the flow of water and mineral salts from roots up to the rest of the plant
11Factors Affecting The Rate Of Transpiration Transpiration is dependent on the opening of the stomata and the evaporation of water in the intracellular spaces of the leafThis is affected by environmental conditions:Humidity of the air – the more water vapour present in the surrounding air, the lower the rate of evaporation from the plantTemperature – which also affects the rate of evaporationLight – which stimulates the stomata to openWind speed – which transports water vapour away from the transpiring surface
12Factors Affecting The Rate Of Transpiration Wiltingcell surface membranecytoplasmWhat happens during wilting?Water escapes from the vacuole.Turgor pressure decreases.The cytoplasm shrinks and the cell membrane pulls away from the cell wall.The cell loses its firmness and becomes soft. The plant becomes flaccid and limp. At this stage, cell is plasmolysed.
13TranslocationThe movement of sugars and amino acids via the phloem is called translocationGlucose produced by photosynthesis in leaf is converted to sugars(mainly sucrose) and translocatedto different partsof the plantTo growing regionsto be used as energy for growthIf the plant requires more energy than can be produced, food stores are mobilised, converted back to sugars, and transported to wherever it is neededTransport in the phloem occurs in both directions up and down the plant (bidirectional movement)To storage organ (fruit)to be stored mainly as sugarsTo storage organ (tubers in roots)To be stored mainly as starch