sec3 bio, chap7, transport in plants

Phloem vessels

________ are living, but have no nucleus (they have cytoplasm)

Lignin & cellulose

________ on cell wall provides mechanical support for plant.

suction force

Def: the ________ which pulls the whole column of water up the xylem vessel from the roots to the leaves.

companion cells

They depend on ________ to carry out metabolic processes and provide nutrients.

amino acids

Def: allows movement of manufactured foods like sucrose and ________ from leaves to other parts of the plant (translocation)

Releases energy

________ for active transport for uptake of mineral salts between the cells 1. water potential of root hair cells> water potential of neighbouring cells; water enters neighbouring cells via osmosis 2. the water dilutes the sap of root hair cell 3. the water potential of those cells will be higher than the cortical cells, thus water is transported via osmosis 4. water continues being transported via osmosis down a concentration gradient to the inner cells until it reaches the xylem vessels water moving up plant transpiration pull.

Cools

________ plant: evaporation of water from cells in the leaves removes latent heat of vaporisation, thus cooling the plant and preventing it from being scorched.

transverse movement

Pits allow ________ across different vessels (xylem → phloem)

Photosynthesis

________: lifts water and mineral salts up from the roots to the leaves so that ________ can occur.

Humidity

________: the more ________ the environment, the less steep the concentration gradient, the lower the rate of diffusion and transpiration 7.5 wilting how wilting occurs 1. turgor pressure ensures that the cells of the leaves are firm and allows for maximum light exposure 2. when rate of transpiration> rate of absorption of water 3. the vacuole and cytoplasm of the cells shrink.

water molecules

Def: allows ________ and dissolved mineral salts from roots to other parts of the plant, provides mechanical support.

Light intensity

________: the greater the ________, the greater the rate of photosynthesis, the greater the rate at which light energy is converted to chemical energy, the greater the rate at which glucose is formed in the guard cell causing the water potential of the guard cells to be higher and water to enter the guard cells down a concentration gradient, the greater the rate at which the guard cell swells and opens, the greater the rate of water evaporation out of the leaf.

Xylem

________ has a thick cell wall, empty lumen, varying lumen sizes in the cross section of a stem phloem vessel.

Companion cells

________ have more mitochondria in order to load sugars from mesophyll cells into the sieve tubes via active transport others epidermis.

def

allows water molecules and dissolved mineral salts from roots to other parts of the plant, provides mechanical support

def

allows movement of manufactured foods like sucrose and amino acids from leaves to other parts of the plant (translocation)

increases sa

v ratio of root hair cells w the soil solution for greater absorption of water molecules

def

the suction force which pulls the whole column of water up the xylem vessel from the roots to the leaves

(def of transpiration stream

the stream of water up the plant) 1. the water potential of the mesophyll cells decreases as water evaporates from them 2. water is drawn from the inner cells nearer to the xylem vessels via osmosis 3. those cells in turn draw water from the xylem vessels, resulting in a transpiration pull transpiration

def

the loss of water in the form of water vapour from all parts of a plant, mainly through the stoma

photosynthesis

lifts water and mineral salts up from the roots to the leaves so that photosynthesis can occur

cools plant

evaporation of water from cells in the leaves removes latent heat of vaporisation, thus cooling the plant and preventing it from being scorched

turgid

water enters the leaf to keep the cells turgid and leaves upright so that there is efficient absorption of light 7.4 factors affecting transpiration rate

light intensity

the greater the light intensity, the greater the rate of photosynthesis, the greater the rate at which light energy is converted to chemical energy, the greater the rate at which glucose is formed in the guard cell causing the water potential of the guard cells to be higher and water to enter the guard cells down a concentration gradient, the greater the rate at which the guard cell swells and opens, the greater the rate of water evaporation out of the leaf

temp of air

the greater the temperature of the air, the higher the rate at which thin film of moisture evaporates

speed of wind

the greater the speed of wind, the greater the speed at which water is blown away in the atmosphere, creating a steeper concentration gradient between the environment and the intercellular air spaces, increasing rate of diffusion and transpiration

humidity

the more humid the environment, the less steep the concentration gradient, the lower the rate of diffusion and transpiration 7.5 wilting how wilting occurs 1. turgor pressure ensures that the cells of the leaves are firm and allows for maximum light exposure 2. when rate of transpiration > rate of absorption of water 3. the vacuole and cytoplasm of the cells shrink

what is the function of the xylem vessel?

allows the water and dissolved mineral salts to move from the roots to the other parts of the plant and provides mechanical support

what are the adaptations of a xylem vessel?

no protoplasm or cross walls, continuous and hollow lumen, pits, lignin and cellulose on cell wall

why does a xylem vessel have no cross walls or protoplasm?

it reduces resistance to water and allows for rapid flow of water and dissolved mineral salts

what is the function of the lignin and cellulose on the cell wall?

provides mechanical support for the plant

what is the function of the pits on the xylem vessel?

allows for transverse movement of water and mineral salts across different vessels

what is the function of the phloem vessel?

allows for translocation, or the transport of manufactured foods like sucrose and amino acids from the leaves to the other parts of the plant

what are the parts of the phloem vessel?

sieve tubes, sieve plates, companion cells

what are the adaptations of a phloem vessel?

no nuclei (only cytoplasm), perforated sieve plates for rapid flow of manufactured foods

what is the function of companion cells?

they have many mitochondria to load sugars from the mesophyll cells into the sieve tubes and to help the sieve tubes with metabolic processes and provide nutrients for them

what is the function of an epidermis?

it has a waxy and waterproof cuticle to prevent evaporation of water from the stem

what is the function of the cortex and pith?

they store substances like starch

state the three methods of translocation studies

studies involving aphids, ringing experiment, radioactive carbon isotopes

state how the study involving aphids is carried out

1. aphids insert their proboscis into the phloem vessel in the stem to obtain food. 2. by cutting the proboscis off and examining the liquid extracted, it can be confirmed that phloem vessel transports manufactured foods

state how the ringing experiment is carried out

1. remove the outer ring of a stem. 2. the phloem vessel is hence removed. 3. the area above the removed ring swells as there is accumulation of sucrose and amino acids.

state how the study involving radioactive carbon isotopes is carried out

1. the plant is provided w co2 that contains radioactive carbon isotopes. 2. the sugars that form also contains radioactive carbon isotopes. 3. under an x-ray, the phloem is seen to also contain radioactive carbon isotopes.

how does h2o move from the soil to roots?

1. they have a lower water potential than the soil. 2. water moves from the soil to the root hair cells via osmosis down a concentration gradient.

what are the 4 adaptations of a root hair cell?

long and narrow, cell surface membrane, concentrated cell sap, many mitochondria

why is a root hair cell long and narrow?

increases sa:v ratio of root hair cells w the soil solution for greater absorption of water molecules

how does a root hair cell's cell surface membrane facilitate movement of water?

it prevents cell sap from leaking out, so that the w.p of the root hair cells is always lower than the soil solution

what is the function of the concentrated cell sap?

ensures that the water potential in the root hair cells is lower than the soil solution, so that water from the soil can enter the root hair cells

why does a root hair cell have many mitochondria?

allows aerobic respiration and releases energy for efficient uptake of mineral salts via active transport

how does h2o move between cells?

1. when water enters the root hair cells, the water dilutes the cell sap. 2. the w.p of root hair cells is higher than the inner cells, so water moves via osmosis down a concentration gradient into those cells. 3. the w.p of those cells is then higher than their neighbouring cells, so water moves via osmosis to those cells. 3. the water continues moving via osmosis until it enters the xylem vessel

define transpiration pull

the suction force which pulls the column of water up the xylem vessels from the roots to other parts of the plant

define transpiration stream

the stream of water up the plant

how does transpiration pull occur?

1. water evaporates out of the intercellular air spaces. 2. the w.p in the spongy mesophyll cells is lower than the inner cells. 3. the water moves from the inner cells into the spongy mesophyll cells via osmosis. 4. the w.p of the inner cells is lower than the w.p of the xylem vessel, so the water enters the inner cells from the xylem vessel, resulting in transpiration pull

define transpiration

transpiration is the loss of water in the form of water vapour from all parts of the plant, mainly through the stoma

how does transpiration occur?

1. water leaves the spongy mesophyll cells and forms a thin film of moisture outside them. 2. water evaporates to form water vapour in the intercellular air spaces. 3. water vapour then leaves the cells into the environment through the stoma, resulting in transpiration

state three reasons why transpiration is important

photosynthesis, cools the plant, keeps cells turgid

explain why transpiration is important for photosynthesis

lifts water and mineral salts up from the roots to the leaves so that photosynthesis can occur (transpiration pull)

explain why transpiration is important to cool the plant

evaporation of water from the cells removes latent heat of vaporisation, therefore cooling the plant and preventing it from being scorched

explain why transpiration is important to keep the cells turgid

transpiration allows water to enter the leaf so that the cells are always turgid and the leaves are firm and gets maximum exposure to sunlight

what are the 4 factors affecting transpiration rate?

light intensity, temperature, wind, humidity

explain how light intensity affects r.o.t

the greater the light intensity, the greater the rate of photosynthesis. the light energy is converted to chemical energy to allow glucose to be formed in the guard cells. the w.p of guard cells is lower and water enters the guard cells causing them to swell and open. the rate at which the stoma opens is hence greater and allows faster water evaporation out of the leaf

explain how temperature of air affects r.o.t

the higher the temperature of air, the higher the rate at which the thin film of moisture evaporates. the concentration of the water vapour in the intercellular air spaces is greater than the concentration of water vapour in the surrounding environment, resulting in a steeper concentration gradient. thus water vapour leaves the cells via diffusion at a faster rate.

explain how wind affects r.o.t

the greater the speed of the wind, the greater the rate at which water vapour is blown away in the environment. this results in a greater concentration of water vapour in the intercellular air spaces as compared to the environment and a steeper concentration gradient. thus water vapour leaves the cells via diffusion at a faster rate.

explain how humidity affects r.o.t

the greater the humidity in the surrounding air, the less steep the concentration gradient of water vapour between the intercellular air spaces and the suurounding environment. hence water vapour leaves the cells via diffusion at a slower rate.

how does wilting occur?

turgor pressure ensures that the leaves are firm and exposed to maximum light. when the rate of transpiration is greater than the rate of absorption of water, the cell vacuole and cytoplasm shrink, the cells lose their turgor and become flaccid and the plant wilts

why may wilting occur?

when the light intensity is too strong, the rate of transpiration is hence higher. when there is too much fertiliser in the soil, the w.p of the soil is lower than the root hair cells and the water moves out of the root hair cells into the soil solution, so the plant has not enough water.

advantage of wilting

the cells become flaccid, the leaf folds up and the sa:v ratio is lower, the guard cells are flaccid causing the stoma size to be smaller and the rate of transpiration is lower causing less loss of water from the plant.

disadvantage of wilting

the cells become flaccid, the leaf folds up and the sa:v ratio is lower, guard cells are flaccid causing the stoma size to be smaller. water is also a limiting factor and the rate of photosynthesis is lower causing the plant to have shortage of manufactured food

explain the movement of h2o

1-2: water molecules move from the xylem vessels (1) into the mesophyll cells (2) down a concentration gradient. 2-3: the water molecules leave the spongy mesophyll cells (2) and form a thin film of moisture on the spongy mesophyll cells. the water molecules evaporate to form water vapour in the intercellular air spaces (3). water vapour accumulates in the intercellular air spaces forming a higher concentration of water vapour comapred to the drier air outside the leaf (5). 3-5: water vapour diffuses from the intercellular air spaces (3) to the stoma (4) and diffuses out of the cells into the environment (5).