Chapter 36 transport in plants 09 03 2015 Water and minerals enter through the root system Co2 enters through stomata in leaves oxygen goes out Oxygen comes in through roots sends out co2 This is why plants won t grow in clay or why they can drown Symbiotic relationship between fungi and plant roots Proton pumps Use energy to pump hydrogen ions out creating electrical potential across cell membrane Can help to bring in other substances through cotransporters Ion channels Specific ions move through the cells in this way Electrochemical gradients Iso equal inside and outside Hypo more water in environment water moves in Hyper more water outside water moves out Plants want to be hyper tonic to its environment Moves from high concentration to low concentration water Aquaporins gated channels that allow for water to move more swiftly across cell membranes How do things get into the roots Apoplastic route o Move from epidermis all the way through cortex without crossing plasma membrane Symplastic route o Goes through plasmodesmata o Cross into one cell Transmembrane o Going to cross every single cell membrane Casparian strip waxy coating around endodermis Anything must go through this to get to the xylem Every route has to go through at least one plasma membrane at the endodermis All vascular plants have tracheids Phloem have two types of cell sieve plate companion cell Guttation only in small plants Droplets of water at leaf margins Hydanthodes escape valves for pressure relief FIGURE 36 13 Adhesion cohesion are very important in transport of water in plants Once the water moves into the xylem there is a continuous column of water from the roots to the leaves Only about 1 of water coming into tree is used for photosynthesis When the stomata is open evaporation occurs Transpiration pulling column of water up and out through the stomata Transpirational pull cohesion clinging of water molecules together adhesion clinging of water molecules to other surfaces all solar powered hyper tonic cells pull more water in as water is released as vapor through stomata water from xylem goes into mesophyll cells Regulation of opening and closing of stomata Guard cells surround the stomata openings If the plant has plenty of water there is no problem opening the stomata so the guard cells become turgid and fill with water o Potassium ions move into the guard cells pulling water into the cells so that stomata will open o Blue receptor senses light which in turn activates and ATP proton pump o Chlorine comes in for stabilization water follows salt If the plant is lacking water the guard cells become flaccid and the stomata remain closed If there isn t enough carbon dioxide in leaves stomata will open Circadian Rhythms plants have internal clocks occur somewhere during the 24 day cells are programmed to do certain things Movement of water only goes one way How things move through the phloem can go both ways From source to sink Mesophyll cell makes sugar Sugar gets sent to the companion cells who them move the sugar into the phloem Moves with a proton pump 1 loading of sugar into companion cells proton pump phloem 2 uptake of water water moves from xylem to phloem creating a pressure that moves the sugar down concentration gradient 3 unloading of sugar into sink cells roots 4 water recycled moves back into xylem 09 03 2015 09 03 2015