Transport in plants Flashcards
what are the plant tissues responsible for transport in the plant
xylem & phloem
why is water important for plants?
- photosynthesis
- solvent for organic food
- replace water lost during transpiration
- keep cell turgid
name the path in which the water moves through the plant (3)
- from the soil INTO the root
- UP the stem
- OUT of the leaf
how is the root hair specifically adapted for absorption of water
- root hair cells are thin-walled -> easy movement of water
- finger-like outgrowth increases the absorption surface
- root hair is in direct contact with the soil solution
- large vacuole ensures a water potential gradient that promotes water absorption by osmosis
discuss passive absorption
T
- absorption of water takes place through osmosis
- moves from the soil solution through thin cell wall and cell membrane into cytoplasm
- when there’s water inside cytoplasm of the cell, osmosis of water continues into vacuole - cell sap of vacuole has a lower water potential & tonoplast is selectively permeable
discuss active absorption
T
most of the mineral salts are passively absorbed with water
some minerals are present in the soil solution in minute quantities that they must be absorbed actively
active absorption needs energy that’s provided by the mitochondria in the cell
name & discuss how water moves through the cortex to the central cylinder
- apoplastic route : 90% of the water moves through the cell walls, lumens of dead cells and hollow tubes of the xylem elements
- symplastic route : water moves through the plasmodesmata & cytoplasm
name 3 forces responsible for the upwards movement of water in xylem
- sucking force😈😏
- root pressure
- capillarity as a result of adhesion and cohesion forces
describe the sucking force used in movement of water up the stem
- strongest force responsible for upwards movement of water in xylem
- water molecules form a continuous chain in xylem
describe root pressure in the upwards movement of water in the stem
- water is continuously taken up by root hairs -> osmotic gradient towards vacuole
- therefore water is literally forced up the xylem of the stem to make room for the water still being absorbed
what is capillarity in relation to how water moves up the stem
- water moves upwards in narrow tubes
* adhesion & cohesion forces cause the upward movement of water
describe what adhesion & cohesion forces are
- AF: forces of attraction between different types of molecules i.e. water & xylem walls
- CF: forces of attraction between molecules of the same sort i.e. water molecules
name 4 reasons why xylem is so suitable for the upwards movement of water
- walls of the wood vessels & tracheids are lined with lignin
- pits allow lateral transport ; water can be evenly distributed
- wood vessels segments and tracheids are connected end-to-end to form continuous tubes
- wood vessel segments & tracheids have no living cell components so nothing interferes with movement of water
how does water move from the xylem to the leaves? (3)
- driven by the pulling force of transpiration
- when the water moves into vascular bundles of leaf it evaporates into surrounding mesophyll cells
- water is used in the palisade & spongy parenchyma for photosynthesis
where does bulk of the water evaporate from?
stomata i.e. transpiration
