transport in plants Flashcards
(17 cards)
why do plants need transport systems?
allows them to have specialised areas increasing surface area to volume ratio
multicellular
what does the xylem do?
transports water and minerals through plant contains dead cells arranged end to end forming continuous vessels when mature vessels =no cytoplasm have hollow central space/lumen where water passes walls of xylem =woody material = ligin
whats life of xylem?
begin as living cells with normal cytoplasm and cellulose cell walls as develop become entangled and original cell walls become impregnated with ligin made in cytoplasm as happens cells die forming hollow tubes lignification makes them very strong and enables them to carry water up tall plants without collapsing ligin=impermeable to water
what is the phloem?
living cells at all stages tubes are formed by cells arranged end to end cell walls = cellulose retain cytoplasm end of each cell formed by cross wall of cellulose with holes = sieve plates which cytoplasm extents through to link each cell with next = long sieve tube
what does phloem transport?
transports products of photosynthesis from leaves to other parts, sugars for energy amino acids for growth carried to young leaves, sugar taken to roots to be converted to starch, for storage, no nucleus controlled by other cells along sieve tubes = companion cells
what is the vascular system of the root?
consists of xylem and phloem
in leaves photosynthesis is used to assimilate h20 with co2 into glucose
phloem transports soluble sugar to plants growing regions flow is bidirectional
xylem is only up to stem
what are vascular bundles?
in root tissue vascular bundles forms central core
in young stem vascular bundles for ring around outer part of stem in older stems vascular bundles form complete ring woody xylem forms core of stem
how is water transported to the root hair cells?
soil water is a weak solution of dissolved mineral ions. sap in root cells is a more concentrated solution than water water enters root hair cell through osmosis passing a permeable membrane h2o moving from dilute soil water to more concentrated cell sap
how is water transported through cells?
as water enters cell 1 contents= more dilute higher water potential than next cell water passes into cell 2 by osmosis making contents more dilute than cell 3 h2o passes into cell 3 by osmosis
how does water get from root cortex tissue to xylem?
process continues until water passes across entire root cortex tissue eventually reaches centre of root particular in xylem vessels which carry h2o up to all other parts of plants
whats transpiration stream?
much of water which plants take in from soil not used in photosynthesis most water lost as water vapour which evaporates from the surface of leaves. loss of h2o evaporates = transpiration water lost by transpiration replaced by continuos coloum of h2o in xylem = transpiration stream
xylem= high water potential and leaf cells = low water potential passes through osmosis
how is water vapour lost?
water evaporates from leaf cells into air spaces within leaf transpiration loss of h2o through stomata into air stomata must be opened at some times for photosynthetic gases
how does h2o get up xylem?
as h2o pulled out xylem lowers hydrostatic pressure at top of xylem creating tension, pulls h2o up xylem by cohesion tension as h2o molecules are attracted to each other pulling one up pulls a chain of h2o molecules up creating column of h2o
what does wind do to rate of transpiration?
rate increases because wind blows h2o molecules away from leaf and increases concentration gradient of water vapour between inside and outside of plant increase rate of evaporation
what does humidity do to rate of transpiration?
rate decreases
humidity increases number of h2o molecules around leaf and decreases concentration gradient between inside ad outside of plant
what does temperature do to rate of transpiration?
rate increase s
water evaporates quicker heat decreases number of h2o molecules surrounding leaves increases concentration gradient
what does light intensity do to rate of transpiration?
rat increases
stomata open to allow for gas exchange and more h2o molecules lost
