Transport in Plants Flashcards
why do plants require a transport system
to ensure all cells receive a strong supply of nutrients
important as substances travel against gravity up the stem
relate the structure of xylem to its function
long continuous columns of dead tissue allowing transportation of water
pits allow water to move sideways between vessels
thickened with lignin providing structural support
relate the structure of phloem to its function
sieve tube elements transport sugars around plant
companions cells designed for active transport of sugar into tubes
plasmodesmata allow flow of substances between cytoplasm of different cells
describe the structure and function of vascular system in the roots
consists of xylem and phloem
xylem arranged in an x shape to provide resistance against force
surrounded by endodermis which are a water supply
describe the structure and function of vascular system in stem
xylem on the inside bundle to provide support and flexibility
phloem on the outside
layer of meristem cells that produce new xylem and phloem
describe the structure and function of vascular system in leaves
forms the midrib and veins
involved in transport and support
define transpiration
evaporation of water from the leaves of plants
consequence of gas exchange as occurs when the stomata open to exchange o2 and co2
name the factors that affect the rate of transpiration
increased light intensity increases transpiration
high temperature increases transpiration
increased wind increases transpiration increased humidity decreases transpiration
waxy cuticle prevents transpiration
how can we measure transpiration
potometer
plant cutting is placed in a water filled tube with an air bubble
rate is calculated by measuring movement of air bubble over time
explain the apoplast pathway
method of osmosis through root hair cells
water moves through cell walls and intercellular spaces
pathway can only be used up until the casparian strip
explain the synplast pathway
water moves through cytoplasm via plasmodesmata
water must be actively transported into cells to begin this
explain the cohesion tension theory
water molecules form hydrogen bonds with other molecules causing them to stick together
surface tension of water also creates effect
as water lost through transpiration, more can be drawn up stem
give adaptations of xerophytes to live in dry conditions
small, rolled leaves
densely packed mesophyll
thick waxy cuticle
closed stomata
hairs to trap moisture
give adaptations of hydrophytes to live in wet conditions
thin or no waxy cuticle
air spaces for buoyancy
open stomata
wide, flat leaves
summarise translocation
sucrose produced in leaves actively loaded into sieve tube elements
lowers water potential causing water to move in to the phloem from the xylem creating high hydrostatic pressure mass flow of solutes down a pressure gradient to the sink
describe the process of adhesion
attraction of water molecules to the impermeable walls of xylem tissue
explain why large multicelluar plants need a transport system
long diffusion distance and diffusion isn’t fast enough
small surface area:volume
explain the benefit to plants of internal transport systems
surface area:volume too small
ensures molecules reach all tissues
allows high metabolic rate
what type of cell makes up the cambium
meristem
explain how the casparian strip prevents ions from reaching xylem of the plant by apoplast pathway
casparian strip is impermeable to water so forces water to pass through cell surface membrane
how does water enter the endodermis
ions enter against the concentration gradient by active transport which reduces water potential of endodermal cells
water moves by osmosis down the concentration gradient
state one similarity between xylem and phloem
both made of cells joined end to end
state two differences between xylem and phloem
xylem vessels contain lignin but phloem only contain cellulose
xylem have a wide lumen but phloem have a narrow lumen
state the function of pits in xylem tissue
lateral movement of water
how can a potometer be used to calculate a more accurate rate of transpiration
potometer is air tight and uses dry leaves
measures the rate of transpiration by measuring movement of air bubbles per time interval
stem cut underwater and mean volume of water loss is calculated
suggest why it is beneficial for the plant for carbohydrates to be transferred throughout plant as sucrose
sucrose is soluble so can be transported in sap
sucrose is relatively metabolically inactive so none used up during active transport
