transport in plants Flashcards
what is the need for a transport system in a multicellular plant?
larger plant have a smaller SA:VOL so have an increased diffusion distance so it wouldn’t be quick enough to supply the volume of the plant with nutrients. sugars are made in leaves but will need to get to other parts of the plant, same for water in the roots
where are the vascular bundles in the stem ? xylem, phloem, cambium
round outside,
phloem =outer most layer
cambium = in-between phloem and xylem
xylem = innermost
what is the function of the vascular bundles in the stem ?
provides support and flexibility to withstand bending forces on stem
where are the vascular bundles in root? xylem, phloem, cambium
xylem - star like shape in middle
phloem - in-between the points of the star of the xylem
cambium - layer inside epidermis (pericycle)
what is the function of vascular bundle arrangement in a root?
provides strength to withstand pulling forces experienced by roots
where is the vascular bundles in a leaf? xylem, phloem
midrib of leaf watermelon shape
xylem = on top of phloem
phloem = round edge of xylem
state the meaning of transpiration
loss of water vapour from a plant to its environment by evaporation and diffusion form roots to leaves
describe how a water potential gradient is maintained during transpiration and causes a water movement to leaves
loss of water vapour from leaves creates a lower water potential in plants creating a concentration gradient between roots and leaves so water moves upwards towards leaves
describe how water moves from cell to outside
water evaporates out of spongy mesophil into air spaces as water vapour where it diffuses out of stomata down a water potential concentration gradient
what are 5 environmental factors that increase transpiration rate
high wind, high light intensity, high temp, high water availability, low humidity
how does an increase in wind cause transpiration rate to increase?
blow away water vapour in air surrounding leaf, increases water vapour potential gradient out o leaf so maintains steep concentration gradient
how does an increase in light intensity cause transpiration rate to increase?
increased rate of photosynthesis, more stomata open to allow more co2 in so more water vapour is able to diffuse out
how does an increase in temperature cause transpiration rate to increase?
water molecules have more kinetic energy so will evaporate into air spaces quicker so therefore increases water vapour potential gradient and rate of diffusion out increases
hotter air can hold higher concentration of water vapour
how does an decrease in humidity cause transpiration rate to increase?
more water molecules in surrounding air, decrease concentration gradient from in to out of leave and therefore decreasing rate of diffusion
how does the structure relate to function of stomata?
thick inner wall- so doesn’t change shape when tugged so stays convex
thin outer wall - moves outwards when turgid so both will create an opening gin the centre for gases