ch9: dandelions is such a perfect song for geraskier Flashcards
describe the adaptations of plants in deserts for water conservation (4)
thick waxy cuticle → ↓ cuticular transpiration
few stomata
open at night when it is cooler
CAM physiology
leaves replaced with spines → ↓ surface area
water storage tissue
extensive roots
explain how abiotic factors affect the rate of transpiration in terrestrial plants (9)
humidity ↑ → transpiration ↓
air spaces inside leaf saturated
↓ conc gradient
temperature ↑ → transpiration ↑
faster diffusion of water molecules
faster evaporation
wind ↑ → transpiration ↑
water vapour blown away from the leaf
↑ conc gradient
light ↑ → transpiration ↑
causes stomata to open
more photosynthesis → low CO2 conc inside leaf → stomata open wider
stomata open to allow gaseous exchange
abscisic acid stimulate closing of stomata
guard cells open/close stomata
2 adaptations of xerophyte plant structures reducing transpiration
explain how temperature affects photosynthesis and transpiration (8)
photosynthesis directly proportional to temp up to optimum temp
low temperatures: limit the rate of light-independent reactions
high temperatures: rubisco denatured → does not fix carbon dioxide
graph
temp ↑ → ↑ transpiration rate
faster diffusion of water molecules
faster evaporation
relative humidity ↓
stomata close at very high temperatures → ↓ transpiration rate
some plants open stomata at very high temps to cool by transpiration
outline the use of models to investigate the transport of water in xylem (3)
models allow 1 factor to be studied independently
capillary tubes: model adhesion between water and xylem vessel walls
porous pot: model flow in a xylem vessel due to transpiration from the leaf
describe how the potometer could be used to demonstrate that the transpiration rate is affected by air movement (3)
a fan is placed so that air blows on the leaves
use different speeds of fan to determine effect of a range of air movement
a control with no air blowing
distance moved by the bubble in a given time is measured
greater distance moved by bubble over time = higher transpiration rate
the bubble is reset to the beginning with the tap
describe how water is carried through a flowering plant (7)
transpiration = loss of water vapour from stomata
water lost from the diffusion of water vapour through stomata + evaporation from spongy mesophyll cells → replaced by water from osmosis through xylem vessels
water pulled out of xylem creates suction → transpiration pull
xylem vessels are hollow tubes
cellulose wall with rings of lignin give strength to resist pressure
due to polarity of water molecules
water molecules are cohesive + adhesion between water and xylem → creates transpiration stream
root hairs provide a large surface area for water uptake
describe how plants carry out gas exchange in the leaves (5)
O2 and CO2 enter/exit the leaf through the stomata by diffusion
O2 & CO2 move through air spaces in the spongy mesophyll
CO2 dissolves in moisture in cell walls
photosynthesis maintains concentration gradients of high O2 and low CO2
guard cells open the stomata during the day
explain the processes by which minerals are absorbed from the soil into the roots (8)
plants absorb mineral ions bound to soil particles thru roots
e.g. potassium, sodium, calcium
minerals dissolve in water
mass flow causes movement of minerals with movement of water through soil
minerals can be absorbed by facilitated diffusion
movement of ions down concentration gradient
minerals absorbed by active transport
against a concentration gradient
requires ATP
occurs through carrier proteins
proton pump transports H+ out of cell → creates electrochemical gradient → +ve mineral ions to diffuse into root cells
-ve mineral ions cross membrane linked to H+ ions moving down gradient
increase surface area for absorption of minerals
branching of roots
root hair cells
fungal hyphae
describe the transport of organic compounds in vascular plant (5)
sugars and amino acids are transported inside plants by phloem tissue
glucose → sucrose
loaded into the phloem in sources and translocated to sinks, where they are unloaded
by active translocation: active transport → require ATP
thru sieve tubes: plasmodesmata provide a path between sieve tubes and companion cell
sources
parts of the plant where photosynthesis is occurring (stems and leaves)
storage organs where the stores are being mobilised
sinks: roots, growing fruits, developing seeds
sucrose → starch → stored in sinks
high solute concentration causes water to enter by osmosis at source
high hydrostatic pressure causes mass flow from source to sink
outline active transport in phloem tissue (3)
sources → sinks
loading in sources
unloading in sinks
pumps → load sucrose into phloem
active transport moves H+ out of phloem → H+ gradient at source
co-transport of sucrose into phloem
explain how aphid stylets can be used to study the movement of solutes in plant tissues (3)
plants grown in radioactive 14CO2 incorporate it into carbohydrates
aphids tap into phloem with their stylets to use sap as a food source
aphid body cut from stylet after it has been inserted into phloem
phloem sap flows through the stylet
radioactive-labelled carbon can be detected in phloem sap
stylets at different parts of the plant can show rate of movement
suggest advantages that vascular tissue confers (4)
easier to stand upright
bigger
put leaves higher in the air to get more sunlight
more efficiently…
translocate sugars from leaves for storage
transport water supply + nutrients from roots to other tissues
explain auxin’s role in phototropism (8)
auxin = plant hormone produced by the shoot tip
make cells enlarge
alter gene expression to promote cell growth
cause transport of H+ from cytoplasm to cell wall
H+ pumping breaks bonds between cell wall fibres → flexible
phototropism is growth towards light
shoot tip senses direction of light
auxin moved to darker side of stem → cause cells on dark side to elongate
outline pollination, fertilisation and seed dispersal (4)
pollination = transfer of pollen to the stigma of a flower
pollen grains grow a pollen tube down the style to the ovule
male and female gametes fuse in the ovary during fertilisation
ovary matures into a fruit
dispersal of seeds depends on the fruit
e.g. pods split open to scatter seeds
outline the metabolic processes that occur in starchy seeds during germination (6)
water absorbed by the seed through micropyle → activates metabolism
plant growth hormone gibberellin secreted
stimulates the production of amylase
hydrolyses starch in endosperm to maltose
maltase hydrolyse maltose to glucose
used in aerobic respiration
production of cellulose for new cell walls
