plant tissues and organs Flashcards
function of xylem
non living transport tissue in plants which transports water and dissolved minerals from soil to roots to leaves
function of phloem
living transport tissue in plants which carries sugars and amino acids from the leaves to the rest of the plant
function of epidermis
outder layer of cells in a plant which protect against dehydration
function of palisade mesophyll
layers of rectangular shaped cells packed full of chloroplast which carry out photosynthesis
function of meristem
rapidly dividing, undifferentiated cells found in growing regions of stems and roots. it differentiates to form other types of cells needed
function of spongy mesophyll
plant tissue with rounded cells, creating air spaces and a large surface area to facilitate the diffusion and exchange of gases
what does the xylem transport
water and dissolved minerals
what does the phloem transport
sugar and amino acids
function of roots
take up water and mineral ions
anchor the plant
function of stem
transports sugars, water and minerals through vascular bundles
supports leaves and flowers
function of leaf
absorb sunlight and carry out photosynthesis
function of flowers
reproductive organs which allow a plant to produce new plants
where is the meristem found
the growing tip of a plant shoot
what is translocation
the process of moving dissolved sugars from the source to where they are needed in the sink, it takes place in the phloem and requires energy -> active process
why is translocation important for plants?
sugars are only produced in the leaves, so they need to be transported to other parts of the plants for respiration
properties/structure of phloem tissue
made up of living cells arranged end to end which develop into tubes. they have cellulose cell walls and contain very little cytoplasm. no nuclei or organelles
kept alive by companion cells
what is the wall at the end of each cell in the phloem tissue called?
sieve plate which contains small pores
what do the small pores in the sieve plate allow you to do?
it allows dissolved sugars to pass from one cell to the next in a long tube
what do garden pests such as greenfly larvae feed on? and what’s the effect
they feed on sugars in the phloem sieve tubes by piercing it with their mouthparts. there is now less glucose for respiration which means less energy is released and less growth
what travels in the phloem
sucrose (NOT GLUCOSE)
what is the transpiration stream
movement of water and dissolved mineral ions from the root to the stem and leaves which takes place within the xylem vessels
what do the walls of xylem vessles contain
lignin (a woody substance) which are impermeable
why is the transport of water and mineral ions so important for plants
it’s needed for photosynthesis and to keep plant cells turgid which keeps the plant upright and prevents it from wilting. mineral ions contain nitrates for growth and magnesium to make chlorophyll
compare structures of xylem and phloem
xylem is made up of dead cells, where as the phloem is made up of living cells. the xylem transports water and dissolved minerals in the transpiration stream, where as in the phloem, sugars are transported. transpiration in the xyelm is a passive process where as translocation in the phloem is an active process which requires energy
what are stomatas
small openings found all over the lower surface of a leaf for gas exchange
what happens when the stomata are open
there’s a steady loss of water from the leaf cells as it evaporates into the internal air space then diffuses out through the stomata
why does the stomata need to be open during the day
to allow carbon dioxide to diffuse in for photosynthesis
why are the stomata closed during night
as there is no sunlight for photosynthesis, so it closes it and reduces the water lost
why is it an advantage to the plant to open the stomata when light intensity is high
because carbon dioxide can diffuse in whilst it absorbs sunlight, allowing it to carry out photosynthesis
suggest how the movement of potassium ions into the guard cells causes the stomata to opene
as potassium diffuses into the guard cells, it means the water potential is lower, which causes water to fill the guard cell via osmosis which makes the cells swell and bend open
why is having a lot of stomata a disadvantage to a plant
a lot of water can be lost, causing the plant to wilt
very little water was lost when the lower surfaces of the leaves were covered in grease, explain why
this is because there are more stomata on the lower surface of the leaf. Since the grease is blocking it, less water can evaporate and get out
explain how mineral ions move from root hair cells to the leaves
the mineral ions are dissolved in water, which travel up the xylem in the plant, and up the stem because of transpirational pull
which two factors increase the rate of movement of mineral ions through the plant
a decrease in the concentration of water vapour in the air
an increase in light intensity causing guard cells to curve/bend more
Potometre required practical:
student repeated investigation but placed the potometre next to a fan blowing air over the leafy shoot
suggest how results would be different
increased of uptake, so there’s more transpiration. higher the air movement, the higher the rate of transpiration
MASS Potometre required practical:
whats the purpose of the polyethene bag wrapped around the plant pot
stops water from evaporating and contributing to the numbers on the scale`
design an experiment using the mass potometre to investigate the effect of changing one of: Light intensity, temperature, humidity or airmovement on the rate of transpiration on a leafy shoot
first place 12 plants which are the same species, with a plastic bag around the whole pot each on a mass potometer. place 4 plants in a dim lit room, 4 in a bright room and 4 in a dark room. measure starting mass for all the plants and leave them in their rooms for half an hour. after, record the final mass of each plant and calculate the percentage change of each plant and work out the mean percentage change for the plants in each light intensity
explain why there is more stomata on the lower side of the leaf
on the lower side of the leaf, there’s more shade which reduces evaporation and prevents excessive water loss
describe how water is transported from the soil to the atmosphere through a plant
the root hair cells absorb the water from the soil via osmosis
the water travels through the xylem vessles to the leaves, caused by transpirational pull where it is lost through the stomata to the atmosphere where it evaporates
