plant transport SLOP Flashcards
which property of water molecules causes cohesion
H bonds between water molecules -> many together can cause water molecules to stick together
what must remain constant in the xylem to enable tension
Xylem must maintain uninterrupted column of water
water is slightly attracted to the walls of the xylem vessels, making transpiration stream easier to maintain - what is the name of this effect and what happens?
adhesion- occurs when water forms H bonds with carbohydrates in cell wall of xylem
function of companion cell
has many organelles that allow sieve tube to function as a normal living tissue
function of sieve plate
allow phloem sap to pass through while filtering organelles
the movement of water through the xylem is driven by hydrostatic pressure differences - explain what this means
water leaves the xylem and enters a leaf by osmosis = this lowers pressure in that section of xylem as vol of water decreases so water is drawn up from stem below
how and why does decrease in light intensity affect transpiration
decreases transpiration -> stomata close in low light decreasing water loss
what is the thin band of tissue on a root cell and what is its function?
casparian strip - waxy layer of suberin prevents water getting past
list 2 reasons why stomata cannot remain permanently closed
- gas exchange for resp + PS
- evaporation of water from stomata drive the transpiration stream, allowing new water to be drawn up into the roots -> replacing water that used to be in metabolic pathways
why are cacti adapted to have spines instead of leaves?
it decreases SA over which water can be lost by evaporation + decrease in stomata
why are cacti adapted to have shallow, broad network of ground roots
allows quick water absorption after rain, since sand doesn’t retain water efficiently
how might leaves folding and rolling inward in droughts reduce water loss
creates pocket of lost water vapour increasing WP around stomata = decreasing diffusion gradient so less water moves out by diffusion
why do aquatic plants (hydrophytes) have spongy arenchyma tissue?
large air pockets -> allowing gases to diffuse quickly + makes plants buoyant
why do aquatic plants (hydrophytes) have reduced root systems?
extensive roots aren’t needed cause water absorbs quickly, water + mineral ions absorbed directly from the water into the leaves
sucrose is described as being ‘co-transported’, what does this mean?
energy not used to move sucrose itself but H ions out of cell. Ions then flow back into cell through transport proteins, bringing sucrose with them
what are sources and sinks
sources - where there is net positive production
sinks - where substances are transported to be used/stored
how might a scientists supply radioactive carbon dioxide to just one leaf?
- surround leaf in airtight container
- cover the stems that enter the container around with gel
- poke a hole in container and use to insert tube
- use to pump radioactive co2
Explain why water in reservoir of potometer is released gradually into capillary using tap
bubble can be used to take measurements over distances longer than lengths of capillary tubing. by using the reservoir to release water and push bubble back to start of ruler, can reset and continue measuring transpiration
why does fan increase the bubble’s rate of movement
usually air made humid by water evaporating from leaves BUT increase in windspeed increases water potential gradient between leaves and air = water evaporates
why does removing the leaves not immediately stop the bubble from moving
-water continues to evaporate slowly from the upper surface where it was cut
-water molecules slightly attracted to one another by H bonds and to walls and xylem and so water can still be drawn up.
what is the tissue found in between xylem and phloem? what is its function?
meristematic tissue - produce stem cells
what is the purpose of parenchyma cells in xylem tissue?
to separate and support vessels
how do bordered pits form and what is their purpose?
where lignin is not present = gaps left in cell wall; bordered pits in 2 adjacent vessels are aligned to allow water to leave one vessel and pass onto the next, as well as leave the xylem.
describe adaptations of xylem vessels that relate to their structure to function?
- lignified walls: support + stretch
- no end walls: columns of water
- pits boarded allows sideways movement of water between vessels
-tubes narrow: column doesn’t break easily
why do sieve tube elements contain no nucleus and very little cytoplasm?
allows space for mass flow to occur
movement of water in xylem and phloem
xylem - upwards
phloem - up and down
how are companion cells adapted for active loading
many mitochondria to produce ATP
why does the presence of starch in the endodermis suggest that an active process is involved?
starch acts as a store of sugars, which can be released and respired to release energy for active processes
describe how water moves up the stem via transpiration pull
tension - loss of water by evaporation from surface of leaf must be replaces by water from xylem. Acts as a suction which pulls water up xylem.
cacti are succulents. What does this mean?
they store water and flesh becomes swollen.
why is it advantageous for some xerophytes to have low water potential inside their leaf cells?
decrease evaporation fo water from cell surface as water potential gradient between leaf surface and cells inside decrease.
what is the difference between active loading and active transport.
active transport is movement of molecules from low to high conc. against conc. grad, pumped using ATP.
Active loading uses active transport to pump H+ ions out of companion cells = movement of sucroses by facilitated diffusion.
