Transport in Plants 3.3 Flashcards
Why do Plants need water?
-Photosynthesis
-Structure and support-turgidity
-Transport dissolved nutrients
-Cooling
Why do plants need transport systems?
-Plants grow throughout their lives so need effective tranport systems to transport nutrients
-Surface area to volume ratio
-Non green plants can’t photosynthesis so need glucose and oxygen transported to them
What is transpiration and translocation?
-Transpiration is where water and mineral ions are transported in the xylem upwards, the process is passive
-Translocation is where sugar and amino acids are transported in the phloem bidirectionally and the process is active
What is found in the vascular bundles?
Xylem, Phloem, Sclerenchyma, Collenchyma, and Parenchyma
What are the functions of Sclerenchyma, Parenchyma and Collenchyma?
-Sclerenchyma provide support and structure
-Collenchyma are involved in growth and strength
-Parenchyma is a soft packing tissue
What are the adaptations of the xylem vessels?
-Cell walls decay and don’t contain cytoplasm or organelles
-The end plates break down leaving a long hollow tube
-Cell walls are thicker than usual to withstand pressure of water
-Cell walls are lignified which makes the cells waterproof, strong and keeps the vessel open but kills the cells
What are bordered pits?
-Non-lignified regions of the xylem vessel that allow water and mineral ions to move laterally between xylem vessels
What are the adaptations of the phloem vessel? and why do they need companion cells?
-Elongated, no nucleus, very little cytoplasm
-The end walls form perforated plates
-Sieve tube elements can’t keep themselves alive so need companion cells to carry out their metabolic function
What are the adaptations of companion cells?
-Large nucleus
-Dense cytoplasm
-Many mittochondria for ATP for active transport
-Infoldings on the cell surface membrane to increase surface area for active transport
What are Cotyledons, Monocots and Dicots?
-Cotyledons= organs that act as food stores for a developing embryo plant
-Monocots= plants that make seeds containing one cotyledon
-Dicots= plants that make seeds containing two cotyledons
What are the roles of water in plants?
-Photosynthesis
-Structure and support: vacuole presses cytoplasm against cell wall
-Transport of dissolved nutrients
-Cooling
What are the adaptations of a root hair cell?
-Microscopic size: penetrate soil particles easily
-Large SA:V
-Thin surface layer: diffusion, osmosis and active transport can take place quickly
-High concentration of solutes to maintain a steep water concentration gradient
What are the three ways water can move from the root hair to the xylem?
1.Apoplast pathway
2. Symplast pathway
3. Vacuolar pathway
Describe the apoplast pathway?
-The continuous flow of water through the open structure of the cell wall due to the pull of water into the xylem and cohesive forces
Describe the symplast pathway?
-Movement of water into the xylem through the continuous cytoplasm connected by plasmodesmata
-Water moves into root hair cell making it have a higher water potential than its neighbour cell so water moves in via osmosis all the way to the xylem.
-Water leaves the cell so there is a steep water potential again and water moves in from the soil.
Describe the vacuolar Pathway?
-Same as the symplast pathway except water isn’t confined to cytoplasm and can travel through vacuoles
-Slower than Symplast pathway
What is the Endodermis and Casparian strip and the importance of the Casparian strip?
-Endodermis: layer of cells surrounding the vascular tissue (xylem and phloem)
-Casparian strip= waterproof layer that runs around endodermal cells
-Its important because it forces water into the symplast pathway and therefore ensures it passes through a selectively permeable membrane
What is root pressure and guttation?
-Root pressure= as water moves into medulla pressure builds up forcing water into xylem pushing water up xylem
-Guttation= loss of water from leaves when root pressure is high
What is transpiration and a transpiration stream?
-Transpiration= loss of water from plants by evaporation
-Transpiration stream= constant movement of water from roots to the leaves. Driven by evaporation of leaves and capillary action
Why do guard cells swell lengthways and not in width?
Cellulose hoops stop them from swelling in width
What is capillary action and mass flow?
-Capillary action= process by which water can rise up a tube against gravity due to polarity of water and hydrogen bonds
-Mass flow= movement of fluids down a concentration gradient
What would happen if there were breaks and bubbles in the xylem and how has it adapted to get around this?
-Any breaks or bubbles would break the cohesion between the water molecules preventing upwards motion
-Bordered pits allow water to move laterally and bypass bubbles and breaks
What is evidence for Cohesion tension theory?
- Cut flowers don’t leak water
- Brocken xylems- they stop drawing water up as cohesion between water is stopped
- Changes in tree diameter- at day during high transpiration rates diameter decreases due to tension
What is the importance of transpiration?
-Tugor pressure= provide hydrostatic skeleton to support leaves
-Cell expansion= tugor drives cell expansion of roots
-Cooling
-Transportation of minerals and assimilates= transported in aqueous solution
-Photosynthesis
