transport in plants Flashcards
why do multicellular plants need transport systems?
big, high metabolic rate, low SA:VOL ratio so they need this to move substances to and from individual cells quickly
what does the xylem tissue transport?
water and mineral ions in solution, move up the plant from the roots to the leaves
what does the phloem tissue transport?
sugars both up and down the plant
how are xylem vessels adapted for transporting water and mineral ions?
long tube like structures
no end walls water passes easily
dead cells so no cytoplasm
walls thickened with woody substance called lignin which supports the vessel and stops it from collapsing inwards
how are phloem tissues adapted for transporting solutes
sieve tube elements - living cells joined end to end to form sieve tubes, no nucleus
companion cells- for each sieve tube element as the lack of nucleus and other organelles means they cant survive on their own. they provide energy for active transport of solutes
where does water enter a plant?
through its root hair cells
what is the symplast pathway?
goes through the living parts of the cell, the cytoplasm.
what is the apoplast pathway?
goes through the non living parts of the cell, cell walls. mass flow (high hydrostatic pressure to low hydrostatic pressure)
how does adhesion help move water through a plant?
water molecules are attracted to the walls of the xylem vessels, this helps water to rise up through the xylem vessels
how does tension and cohesion help move water through a plant?
water evaporates from leaves at the top of the xylem (transpiration)
this creates a tension (suction) which pulls more water into the leaf
water molecules are cohesive (stick together), so when some are pulled into the leaf others follow. this means a whole column of water in the xylem from the leaves down to the roots, moves upwards
water enters the stem through the root cortex cells
what is transpiration?
its the evaporation of water from a plants surface, the leaves
what is transpiration a result of?
gas exchange
plant opens stomata to let CO2 in for photosynthesis, this lets water out at the same time as higher conc inside than out
what are 4 main factors that affect transpiration rate?
light (stomata opens when it gets light)
temperature (warmer water molecules have more energy so evaporate from cells inside leaf faster)
humidity (the lower the humidity , faster rate. air around plant dry, water potential gradient increased between leaf and air )
wind ( windier, the faster rate as lots of air movement blows away water molecules from around the stomata which increases the water potential gradient
what is used to estimate transpiration rate?
potometer
where are xerophytic plants adapted to live in?
in dry climates