7- transport in plants Flashcards
Parenchyma
- cells serve to support plant when turgid
- prevent plant from wilting
- packing+storage
- cells carry out photosynthesis
collenchyma
living cells with unevenly thickened cellulose cell walls- responsible for providing support
schlerenchyma
dead cells with lignified walls- support
What is the main function of companion cells in phloem tissue?
release energy for sieve tube elements
xylem vessel features
- elongated cells with end walls broken down,
- located in vascular bundles in stem+centrally in roots
vascular tissue in leaf
transport water and nutrients
companion cell features
release energy for sieve tube elements
what is the relationship between humidity and the water vapour gradient between the leaf and atmosphere
high humidity decreases the water vapour gradient
describe the adhesion of water molecules in the xylem
hydrogen bonding between polar water molecules and non-polar cellulose in xylem vessel walls
what do stomata do in the water movement process in plants
allow water to evaporate from leaves
According to the mass flow hypothesis, what happens at the source to initiate translocation?
solutes like sucrose are actively loaded into sieve tube elements
Which of the following is a source of assimilates for translocation?
leaves
How are hydrogen ions (H+) involved in the active loading of sucrose into the phloem?
co-transported with sucrose into companion cell
Describe the difference in leaves of monocotyledon and dicotyledon?
leaves in monocotyledon are long, narrow - have no petiole and have parallel veins (grass)
The leaves in dicotyledon are leaves with blades, they are wide, petiole is present and have branched veins
Describe the difference in the stem of monocotyledon and dicotyledon?
Monocotyledon have scattered vascular bundles or as dicotyledon have vascular bundles which are arranged in a ring
where are xylem + phloem distributed in the stems, roots, leaves of plants
stems: vascular bundles arranged forming ring around outer part of stem
roots: vascular bundles found in centre
leaves: form networks of veins in leaf
how does companion cell structure relate to function
large number of mitochondria+ribosomes, provide energy and proteins for active transport of substances
what are diff tissues in a typical plant leaf and their functions
upper epidermis with waxy cuticle: reduces water loss
palisade mesophyll: photosynthesis
spongy mesophyll: has air spaces for gas diffusion
lower epidermis: has stomata surrounded by guard cells for gas exchange
vascular tissue: transports water and nutrients
State two environmental factors that affect the rate of transpiration.
For each factor given, explain how it affects the rate of transpiration
Temperature: increased temperature increases the rate of evaporation/diffusion OR at high temperatures, stomata close so transpiration stops
Humidity: increased humidity decreases rate of transpiration as the water potential gradient is less steep
wind speed OR air movement: Higher wind speed causes a steeper water potential gradient OR at high wind speed, stomata close and transpiration stops
water availability: reduced water availability causes stomata to close and transpiration stops OR when more water is available, there is a steeper water potential gradient between roots and leaves, so transpiration is faster
light intensity: higher light intensity increases transpiration rate as more stomata open OR at very high light intensity, stomata close so transpiration stops
function of vascular tissues
form transport systems in plants. Xylem transports water and minerals whereas phloem is used for TRANSLOCATION of sucrose and amino acids from the source to the sink
location of xylem
- in stem facing the center and arranged in vascular bundles
- in roots, it has a series of arms between which the phloem is found
location of phloem
in stem together with xylem forming vascular bundles that are surrounded by sclerenchyma, as phloem faces outwards.
in roots, found between a series of arms made of xylem vessels
What is the xylem vessel element?
dead, lignified cell found in xylem so specialized for transporting water and for support The ends of the cells break down and join with neighboring elements to form long tubes called xylem vessels
xylem vessel
dead empty tube with lignified walls through which water is transported in plants it is formed by xylem vessel elements lined up end to end
