Transport In Plants Flashcards
Xylem transports
Water and mineral salts
Long, narrow, hollow tubes whose walls are lined with lignin ligninfied
Xylem have no cross walls and therefore allow for the continuous flow of water
Cells therefore permeable membrane
Water moves through a plant
Root pressure
Transpiration
Capillarity
Root hair
Extension of a single epidermal cell
Increases the surface are of the roots
Cortex/pith
Packing tisse, spherical unspecialised cells packed loosely
Vascular cambium
Constantly dividing cells between the xylem and phloem to form the xylem on the inside and phloem on the outisde
Epidermis
Single layer of cells (flatten
Bark
Waterproof layer composed of cork cells
Cork cambium
Constantly dividing cells to form cork on the outside
Lignin- xylem vessels
Tough and strong helps the xylem vessels support the plant
Root pressure
Push from the roots
Water enters root hairs and epidermal cells of roots by osmosis,
Water travels up the cortex of the root by osmosis
Water is pushed up the xylem vessels of the roots to the bottom of xylem vessels of the stems by the water entering the roots and epidermal cells (root pressure is a push from the roots)
Transpiration
Is a loss of water vapour from the surface of the leave which creates a pull
Water evaporates from the spongy mesophyll cells diffuses out of them through the air spaces and exits through the stomata, more water is pulled from the spongy mesophyll cells by osmosis, this pull/loss of water brings/draws the water in the xylem vessels of the stem to the xylem vessels of the leaves and into the palisade mesophyll cells where it is used for photosynthesis
Capillarity
Helps water move
The cohesion of water molecules between the molecules in the walls of the xylem vessels allow for a continuous flow of water from the roots and helps water move upwards
Transpiration stream
Flow of water through xylem vessels
Control of the loss of water by stomata
Stomata found in the lower epidermis of leaves, open and almost close depending on the turgidity of the guard cells.
If the guard cells are turgid, meaning alot of water(supply of waterin the soil), this means rapid Transpiration
If they are flaccid meaning less water, or water loss, Transpiration decreases
Environmental factors affecting rate of Transpiration
Wind speed
Humidity
Light
Temperature
High temperature low temp
High temp causes water to evaporate quickly and water vapour to diffuse rapidly
Low temp causes water to evaporate slowly and water to diffuse slowly so Transpiration is slowe
Wind speed
Windy conditions water vapour is pulled from the surface of the leaves quickly
Humidity
High humidity the surface of the leaves are saturated with water vapour decreasing the concentration, hence diffusion is slowed and Transpiration slowed
Light intensity
Dim light the stomata almost close, very little water vapoyr can duffuse out reducing the rate of transpiration
Importance of Transpiration
- It cools the leave as water moves through it
- For photosynthesis draws water to palisade cells
- Keeps stems turgid due to the flow of water
- Moving water dissolves mineral salts
Water conservation in plants
Reducing the rate of Transpiration
1. Plantas shed their leaves in dry seasons and winter months
2. Leaves have extra thick waxy cuticles
3. Some Leaves have reduced numbers of stomata
4. Stomata are grouped together in sunken pits that trap water vapour
Have fine hair on their surface that water vapour
Storing water in plants
Many succulent plants store water in their leaves aloe
Many succulent plants store water in the stems cacti
Roots of some plants store water
Increasing water uptake
Some plants have long vertical deep plant roots to ABSORD water from deep within the soil
Some plants have shallow widespread root (ROOT SYSTEMSs to obtain water from the surface of the soil in a wide area
Pholem sieve tibes
Phloem vesels have sieve plates, companion cells that control the functioning of the cells transports organic food mainly sucrose and amino acids contains living cytoplasm
Sugar sources
Produce sugars where the phloem obtains sucrose from e.g. photosynthesizing leaves
Sugar sinks
Parts of plants that require sugars fruits, seeds, stems roots
Mechanism of translocation
Sugars move from the cells of the Sugar source to the pholem by active transport, increases the sugar concentration inside the phloem sieve tubes
Water moves from the xyelm vessels into the adjacent phloem sieve tube by osmosis
Turgor pressure increases as water increased and the turgor pressure forces the sugars and organic food/dissolved substances through the sieve plates
Sugars diffuse through the walls of the phloem into the cells of the sugar sink such as a fruit or seed and sugar concentration decreases
Water then dawn back into the xylem vessels by the suction created by the Transpiration stream and the turgor pressure inside the sieve tubes decreases once again
Movement of mineral salts
Mineral salts are absorbed by the roots in the form of ions, they are dissolved in water present in the soil, move up by active transport where they enter the xylem vessels and carried thright the plant
Importance of FOOD STORAGE in living organisms
- Overcomes the need for continuous food intake by heterotrophs and continuous food manufacture by autotrophs
- It provides food reserves in times of food scarcity in heterotrophs e.g. winter months and in times where food manufacture does not occur in plants e.g. during a drought
enables hibernation in animals and plants to survive during dry season or winter months
it provides food reserves for special functions like the growth and development of an embyronic plant, new plants use stored food as they develop from vegetaive organs
hydrolysis and condensation
the splitting of molecules by the addition of water
substances hydrolysed are: amino acids, fatty acids and glycerol and glucose
the joining of molecules by the loss of water
substances condensed are: starch, glycogen, proteins, and lipids and fats
food storage in animals
storage in adipose (fat) tissue, excess fat is stored around organs and under skin, excess glucose is converted to fat and stored
storage in the liver
vitamins A, B12, D
Iron
Glycogen formed by the condenstaion of excess glucose in blood
storage in skeletal muscle
store glycogen formed from the condensation excess glucose in the blod
storage of food in plants
fruits, stems, leaves, roots, seeds
the phloem sieve tubes transport sugars produced in photosyenthesis (and amino acids), to the above structures, where they are stored or converted to proteins, lipids and starch and stored
storage in vegetative organs
STORE STARCH MIANLY
vegetative organs are undrground structures that are swollen with food at the end of growing seasons
they allow the plant to survive during the unfavourable season and allow it to grow rapidly, using stored food during the favourable season
they can also act as a means of sexual reproduction as new plants grow from the vegetative organs
vegatative organs
stems
stem tubers
english potato yams
rihzomes ginger
corms
eddo
vegatative organs
roots
root tubers
sweet potato
vegatative organs
leaves and leaf bases
such as bulbs that grow from the leaf or make up the bulb
ONIONS ARE BULBS
storage in TAP ROOTS
tap roots are single vertical roots.
sugars: carrot and sugar beet
starch: turnip
storgae in succulent fruits
store mainly sugars
e.g. mango and pawpaw
fats and oils
avocado and olives
starch
breadfruit
thse stored fods attract anumals to eat it and aids in seed dispersal
storage in seeds
the cotyledons and endosperm of seeds can store starch
e.g. rice and wheat
store proteins
peas and beans
store oils
nuts
STORED FOOD SUCH AS THOSE LISTED ABOVE IS USED WHEN THE SEEDS GERMINATE
STORAGE IN LEAVES
MANY LEAVES OF SUCCULENT PLANTS STORE WATER
E.G ALOE
Storage in stems.
the stems of sugar cane store sucrose, some succulent plants store water in their stems
why do we need to cut the stems of celery underwater
This process is called transpiration. That new empty space inside the leaves creates a low pressure, and like a drinking straw, this low pressure allows water below the leaf to travel up the stem. You’ll see the little tubes the water travels up when you cut the celery stem, and you can see the colour up in the leaves.
Why air bubbles are not good.
Cut the stem of the leafy shoot (at an angle to increase the surface area) under water . The reason we cut it under water is to prevent air bubbles entering the xylem vessel.
Water will no longer move up the xylem as a continuous column, as the transpiration pull will not occur if there are air bubbles.
How a potometer works
the moving-bubble potometer, which measures water uptake by the shoot. (Note that water
uptake in a cut stem is likely to be greater than that in a rooted plant. This is due to the direct access to xylem vessels
in a cut shoot, rather than resistance to this across the apoplast in a rooted plant.
