3.1.3 Transport In Plants Flashcards

Question

Movement of water into the root

Answer 1

Root hair cells are the exchange surface in planhs where water is taken imto the body from the soil - root hair is a long thin extension of a root hair cell (specialsied epidermal cell found near meristem root tip)

Answer 2

Microscopic size means they can penetrate easily between soil particles Large SA:V with there being thousands of them Thin surface layer through which diffusion and osmosis takes place quickly Concentration of solutes in cytoplasm mainatains a water potential gradient between cell and soil water

Answer 3

Soil water has high water potential (low concentration of dissolved compounds) and cytoplasm and vacuole sap of the root hair cells contain many solutes meaning water potential is lower - water moves into the cells Cellulose cell wall (thin)

Answer 4

Symplast | Apoplast

Answer 5

Continuous cytoplasm of living plant cells which is commected through the plasmodesmata - VIA OSMOSIS. Root hair cell has a higher water potential than the next cell along - this is because of water diffusing in from soil which makes the cytoplasm more dilute (higher water potential). This process of osmosis comtinues from cell to cell across root until the xylem is reached

Answer 6

As water leaves root hair cell water potential of cytoplasm in root hair cells drops - low water potential - ensuring that the steep concentration gradient from soil to cells is maintained

Answer 7

Movement of water through cell walls and intercellular spaces - water fills the spaces between the loose, open network of fibres in the cellulose cell wall. As water molecules move into xylem - mlre water molecules wre pulled through ghe apoplast due to cohesive forces ; this pull from water moving into the xylem and up the plant creates a tension that means there is a continuous flow of water through the open structure pf the cellulose wall with little resistance

Answer 8

Apoplast snd symplast pathways until it reaches rhe endodermis - layer of cells surrounding the vascular tissue

Answer 9

It is a band of waxy material called suberin that forms a waterproof layer around the endodermal cells. WATER IN APOPLAST (CELL WALL) can go no further and is forced into cytoplasm

Answer 10

This diversion is important as to get there water must pass through selectively permeable membranes - thus filtering out any potentially toxic solutes from reaching living tissues (no carrier proteins to admit them)

Answer 11

Solute concentraion in cytoplasm of endodermal cells much lower rhan in xylem and endodermal cells move mineral ions into the xylem by active transport - therefore water potential of xylem cells is much lower rhan water potential of endodermal - INCREASES RATE OF WATER MOVING INTO XYLEM VIA OSMOSIS DOWN A WATER POTENTIAL GRADIENT (through symplast)

Answer 12

Water returns to the apoplast pathway to enger the xylem itself and move up the plant - active pumping of mineral ions (to produce movement of water by osmosis) results in root pressure. Root pressure gives water a push up the xylem and is independent from transporation

Answer 13

1) Poisons like cyanide affect mirochondria and prevent production of A - ic cyanaide is applked to root cells, root pressure disappears 2) Root pressure falls with a fall in temperature and vice versa therefore chemical reaction involved 3) Levels of oxygen/resporatory susbatnces fall then root pressure falls 4) Xylem sap may exude from the cut end of stems at certajn times; forced out of special pores at the ends of leaves in some conditions (overnight - when transpiration is low : guttation)

Answer 14

Compromise between gaseous exchange for photosynthesis (taking in CO2) and losinf the water needed for turgir pressure and transport. Large SA:V to capture light but this increases risk of water loss through transpiration

Answer 15

Waxy cuticle Stomata on underside of leaf Roots that grow down to water in the soil

Answer 16

In habitats where often there is a very dhort supply of water + hot dry and breezy conditions, water will evaporate from leaf surfaces rapidly

Answer 17

Plants in dry habitats have evolved a wide range of adaptations that enable them to live and reproduce in places with low water availability

Answer 18

Conifers, Marram grass (found in sand dunes and coastal areas - dry and salty) Many plants that survive in very cold and ice conditions also xerophytes - water is not freely available because it is frozen CACTI

Answer 19

Most plants up to 10% is through cuticle - extra thick layer minimises water loss and this is common in evergreen plants which allows them to survive both hot dry summers and cold winters when water can be hard to absorb from ground

Answer 20

Stomata located in pits - reduces air movmeent and produces a microclimate of still, humid air = lower water vapour potential gradient thus less transpiration

Answer 21

Reduces water loss bur also reduces gas exchange

Answer 22

Water loss decreases as leaf area decreases ; also have thin needles to reduce SA:V, minimising water lost in transpiration

Answer 23

Microclimate of still, humid air and reduces water vapor potential hrsdient - minimising water loss… marram grass even have microhairs in the sunken stomatal pits

Answer 24

Confines all of the stomata within a micro environment of still, humid air to reduce diffusion of water vapour from the stomata. MARRAM GRASS

Answer 25

Store water in soecialised parenchyma tissue in their stems and roots - swollen/fleshy and water is stored when in plentiful supply + used in times of drought. Aloes are succulants + salicornia

Answer 26

Lose their leaves when water is not available - Palo verde sheds ifs leavss and teunk turns green to photosynthesise with minimal water loss

Answer 27

Many xerophytes have root adaptarions thar help them to get as much water as possible from fhe soil ; long tap roots can penetrate several metres so they can access water stored much lower. Mass of widespreadh shallow roots - can absorb kode water before shower evaporated (CACTI HAVE BOTH ADAPTATIONS) MARRAM = LONG VERTICAL PENETRATION

Answer 28

Mat of horizontal rhizomes (modified stems) from shich many more roots develop to form an extensive network that enables sand to hold more water

Answer 29

Plants may lose leaves and become doemant or die completely ; some survive as storage organs such as bulbs, codms or tubers. Some can survive toral dehydration and appear dead but when rain comes the cells recover, become turgid and green again to photosynthesise - DISACCHARIDE TREHALOSE ALLOWS THIS

Answer 30

Plants thar are submerged in water (or on surface) - which need special adaptations to cope with growing in water or in permanenlty saturayed soil

Answer 31

Water lilliee, water cress, duckweeds and bulrushes/yellow iris

Answer 32

Float - so they are near the surface to get the light needed for photosynthesis

Answer 33

Warer logging - air soaces need to be full of air and not water to survive

Answer 34

No need to conserve water as there is always planet available so transpiration is not an issue

Answer 35

Always open stomata on upper surface - maximises gas exchange and no risk to loss of turgor due to abundance of water so guard cells inactive with stomata always open. Floating leaves means stomata must be on top side of leaf in contact with air

Answer 36

Water supports leaves and flowere (turgor pressure) - no need for strong supporting structure

Answer 37

Spread across water to capture as much light as possible

Answer 38

Water can diffuse directly into stem and leaf so less need for uptake theough roots

Answer 39

Maximises area for photosynthesise and for oxygen to difffuse into the submerged plant

Answer 40

Allows them to enable leaves/flowers to float to the surface of the water

Answer 41

Specialised parenchyms packing tisue that forms in stems, leafes and roots : MANY LARGE AIR SPACES FORMED BY APOPTOSIS

Answer 42

Makes the leafes/stems more buoyant Forms a low resistance infernal pathway for movement of O2 to tissues below the water; allows them to cope with anoxic conditions in the mud.

Answer 43

Also provides a low resistande pathway by which methane produced by the rice plants - nothing can be vented into the atmosphere - contributed to greenhouse effect and resulting climate change

Answer 44

Roote can beckme waterlogged - special arial roots called pneumatophores grow upwards into the air

Answer 45

Water is transported from the roots and carbon dioxide into the leaf from the air ; diffuses into the leaf down a concentration gradient from air spaces within the leaf. O2 moves out of the lead cells info air spaces by diffusion down s concentration gradient. Water too evaporates into air spaces

Answer 46

By diffusion theough stomata - they can be opened and closes by guard cells which surround the stomatal opening

Answer 47

This loss of water fapour from the leaves and stems of plants ; an inevitable consequence of gaseous exchange

Answer 48

During the day a plant needs to take in CO2 for photosynthesis and at night when no oxygen is being produced by photosynthesis, it needs to take in oxygen for cellular respiration therefore some stomata are open at all times

Answer 49

Here it moves by osmosis across membranes and by diffusion in the apoplast pathway from the xylem through the cells of the leaf where it evaporates from the freely permeable cellulose cell wallss of the mesophyll into the air spaces. Then it moves down the concentration gradient into the external air through stomata : TRANSPIRATION STREAM

Answer 50

Water molecules evaporate from surface of mesophyll into the air spaces in the lead and move out of the stomata into surrounding air by diffusion down a concentration gradient. Loss of water by evaporation from a mesophyll cell lowers the water potential of the cell so water moved into the cell from an adjacent cell by osmosis along symplast and apoplast pathways. Repeated across leaf to the xylem (ater moves out of xylem through osmosis)

Answer 51

Water forms hydrogen bonds tih carbohydrates in the walls of the narrow xylem vessels (adhesion). Also form hudrogen bonds eith each other - cohesion. Combined effect results in capillary tube action ; water can rise up a tube agsindt force of gravity (narrow). Water is drawn up in a continuous stream to replace the water lost by evaporation - this is the transpiration pull. Transpiraiton pull also results in tension in xylem which helps to move water across the roots from the soil

Answer 52

- When transpiration is at highest during the day - pressure in xylem increases thus diameter of treee trunk decreases. At night when transpiration is lowest, the diameter increases because tension is low - When a xylem vessel is broken ; air is drawn up into xylem rather than water leaking out thus palmt can no longer move water uo the stem because cohesive forces are broken (no continuous stream)

Answer 53

Very difficult to separate water vapour from transpiration and respiration + evaporationg/condensing to collect all water that leaves. Therefore we measure the uptake of water as about 99% of this is lost through transpiration. USE A POTOMETER

Answer 54

All joints sealed with waterproof jelly to make sure any water loss measured is as a result of transpiration from the stem and leaves Stem of fresh root is cur under water and transferred to prevent any air bunnles neinf introduced - if cut in the air it would introudce air bubbles cutting off continuous transpiration stream

Answer 55

Distance moved by air bubble/time taken for air bubble to move that distancd

Answer 56

``` Indepedent = environmental conditions Dependent = rate of transpiration Control = species of plant tested, amount of time for transpiration, soil they grew in, volume of water, ```

Answer 57

Opening and closing of stomata - turgor driven process ; when turgor is low the guard cell walls are closed and when conditions are favourable, guard cells pump in solutes to then increase turgor. Inner wall is thicker than thinner outer wall thus cells become bean shaped and open the pore ; hormonal signals can trigger turgor loss from guard cells which close the stomatal pore and conserve water

Answer 58

``` Light Humidity Temperature Air movement Soil water availability ```

Answer 59

Light causes stomata to open for gas exchanhe ; increasing number of open stomata = increases rate of water vapour diffusing out and increasing evaporation from surface of the leaf. PROPORTIONAL

Answer 60

High humidity lowers transpiration rate because of reduced water vapour potetnial gradient between inside of leaf and outside air. Very dry air has oppsoite effect and increases transpiration rate

Answer 61

Increases KE of water particles and thus increases rate of evaporation from sppngy mesophyll into air spaces Increases the amount of water vapour air can hold until it gets saturated so it decreases relative humdity Both factors increase diffusion gradient inside and outside thus increasing rate of transpiration

Answer 62

Fewtures like hairs decrease air movement close to the leaf - water vapour accumulates here and so water vapour potential around stomata increases thus reducing gradient. Air movement will INCREASE RATE OF TRANSPIRATION and still air will decrease transpiration rate

Answer 63

If very dry the plant will be under water stress and rate of transpiration will be reduced

Answer 64

Leaves produce glucose which is then converted to sucrose - when it reaches the cells where it js needed, it is converted back to glucose for respiration or to starch for stirage or used to produce amino acids

Answer 65

Sources to sinks in translocation ; an active process which requires energy to take llace and substances to be transported both up and down the plant

Answer 66

The products of photosynthesis fhat are transported

Answer 67

Sucrose - makes up about 30% of the phloem sap content

Answer 68

Green leaves and green stems Storage organs such as tubers and tap roots that unload their stores Food stores in seeds when they germinate

Answer 69

Roots that are growing or activeky absorbing mineral ions Meristems that are active,h dividing Parts of the plant that are laying down foot stores such as dwveloping seeds, fruite or storage organs

Answer 70

Solubke products of photosynthesis are moved into phloem from the sources by an active process - sucrose is the main carbohydrate that is transported and is not hsed un. Metabolism as readiy as glucose thus less likely to be metabolised during the transport process

Answer 71

One is large,y passive and the other is active

Answer 72

Sucrose travels through cell walls and inter-cell spaces to the companion cells and sieve elements (apoplast route) by diffusion down a concentration gradient, miantained by removal of sucrose intk thr phloem vessels. In companion cells sucrose is moved into cytoplasn across cell membrane in an actibe process - H+ ions are actively pumped out of the companion cell into surrounding tissue using ATP ; these ions then return down the concentration gradient ejth sucrose thus increasing sucrose concentration in companion cells and sieve elements through plasmodesmata

Answer 73

Have many infoldings in their cell membranes to give a large SA for active transport of sucrose into cell cytoplasm and also many mitochondris to supply ATP needed for transport pumps

Answer 74

Water moves into phloem via osmosis - leads to a build up in turgir oresshre due to rigid cells walks andthe water carrying the assimilates moves into the tubes of the sieve elements, reducing pressure in companjon crlls andthus moving up and down the pksnt by mass flow to areas of lower pressure (sinks)

Answer 75

Solute accumulatuon in source phloem leads to an increase in turgor pressure fhat forces sap to regions of lower pressure in sinks ; these pressure differences are what allow solutes and water to berapidly transported over many metres

Answer 76

Sucrose is unloaded from phloem at any point into cells that need it ; main mechanism is just diffusion of sucrose from phloem into surrounding cells. It moves in rapidly or is converted to another susbtance (such as strach/glucose) to maknfain a concentration gradient between ohloem and surrounding cells

Answer 77

Leads to a rise in water potetnial of the phloem ; water moves outingo surrounding cells by osmosis and some of that water that carried the soljtes is drawn into the transpiration stream

3.1.3 Transport In Plants Flashcards

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