Transport in plants Flashcards
The transport of minerals over longer distances through vascular system is called
Translocation
The direction of transport of water and minerals through xylem is
unidirectional
The direction of transport of organic compounds or withdrawal of nutrients during senescence is
multidirectional
Passive transport of molecules over short distances occur by
Diffusion
Gaseous movement within the plant body occurs only through
diffusion
Diffusion rate is affected by membrane permeability, temperature, pressure and ______
Gradient of concentation
Hydrophilic substances pass through the membrane by
facilitated diffusion
The pre-requisite for facilitated transport is the presence of carrier protein and ____
Concentration gradient
Facilitated diffusion is accomplished with the help of _____ proteins
Carrier
The diffusion in which proteins move substances across the membrane without the expenditure of energy is called
facilitated diffusion
Facilitated diffusion is very specific and is sensitive to ____ which react with protein side chains
Inhibitors
The protein that form large pores in the outer membranes of the membranes of the plastids, mitochondria and some bacteria allowing molecules up to the size of small proteins to pass through are called ____
Porins
Water channels are composed of ___ different types of aquaporins
Eight
The type of facilitated transport in which two molecules move across the membrane in same direction is called
symport
The type of facilitated transport in which two molecules move across the membrane in opposite directions is called
antiport
The type of facilitated transport in which a molecule across a membrane independent of other molecules is known as
Uniport
The transport in which energy is used to transport molecules against concentration gradient is called
active transport
The proteins which use energy to carry substances across the cell membrane are known as
pumps
Pumps are sensitive to inhibitors that react with
protein side chains
The transport which requires a carrier but no energy is referred to as
facilitated diffusion
The mode of transport which does not require any energy and occurs only along the gradient
diffusion
The medium required for dissolution of most of the substances in plants is
water
Water taken yp by terrestrial plants get lost to air by the process called
transpiration
Solute potential and pressure potential are major determinants of ____ potential
water potential
Highest water potential is possessed by
pure water
Water potential is denoted by
Psi
Water potential of solutions is always ____ than that of pure water
less
The lowering of water potential due to dissolution of solute is called
solute potential
For a solution at atmospheric pressure, solute potential is equivalent to _____
water potential
If a pressure greater than atmospheric pressure is applied to pure water, its water potential ____
increases
Turgidity ____ the pressure potential
Increases
Negative pressure potential or tension in which vascular tissue plays a major role in water transport up a stem?
water column in the xylem
The part of the cell that mainly contributes to the solute potential of cell is
central vacuole
The membrane of vacuole is called
tonoplast
Diffusion of water across a selectively permeable membrane is called
Osmosis
The direction and rate of osmosis depends on both the gradient of _____ and _____
pressure and concentration
Osmotic potential is eual to osmotic pressure but with ____ sign
negative
External solution is said to be ____ when it balances the osmotic presure of the cytoplasm
Isotonic
If the external solution is more dilute than the cytoplasm, it is called
Hypotonic
Cell swell up when placed in
Hypotonic solution
When placed in hypertonic solution, cells ____
shrink
The process of water moving out of the cell and cell membrane getting shrinked from cell wall is called
Plasmolysis
During plasmolysis, water is first lost from the ____
cytoplasm
The phenomenon of cell shrinking away when placed in ___ solution is called plasmolysis
hypertonic
There is no net flow of water towards inside or outside when the cell is placed in an ___ solution
Isotonic
When the outer and inner environment of cell are in equilibrium, the cell is said to be
Flaccid
Water while diffusing into a cell causes cytoplasm to build up a pressure against wall, called
Turgor pressure
The tugor pressure exerted by protoplasm due to entry of water against rigid cell walls is called ___ pressure
pressure potential
The pressure responsible for enlargement and extension growth of cells is
Turgor pressure
The special type of diffusion when water is absorbed by solids or colloids causing them to increase in volume is called
Imbibition
The absorption of water by seeds is an example of
Imbibition
The movement of water during imbibition is _____ the concentration gradient
along
Movement of water in plants usually occurs through
Xylem
The system by which water, minerals and food are transported in plants across long distances is called
Bulk/ mass flow system
Bulk flow in plants is usually achieved through _____ gradients
Hydrostatic pressure
The bulk movement of substances through the vascular tissues of plants is called
Translocation
The vascular tissues associated with translocation of water, mineral salts, some organic nitrogen and hormones from roots to aerial parts of the plant is
Xylem
Translcation of organic and inorganic solutes occur mainly from leaves to other parts of plant through
Phloem
The responsibility of absorption of water and minerals from soil through roots is of
Root hairs
Root hairs are thin - walled slender extensions of root _____ cells
Epidermal
Absorption of minerals and water in root occur through the process of
Diffusion
The two pathways involved in movement of water into root layers after absorption are
Apoplast and symplast pathway
The apoplast system is continous throughout the plant except at ______
casparian strips
The movement of water which occurs through intercellular spaces and walls of cells is
Apoplastic
The pathway for movement of water which does not involve crossing the cell membrane is called
Apoplast pathway
The _____ does not provide any barrier to water movement and water movement is through ___
apoplast; mass flow
Mass flow of water in apoplastic movement is due to which two properties of water?
Cohensive and adhesive
The symplast system is the system of interconnected _____
Protoplast
Intercellular movement of water in symplastic pathway occurs through _____
Plasmodesmata
The movement of water aided by cytoplasmic streaming is called
Symplastic movement
Majority of water flow in roots occurs via which pathway?
Apoplast
Endodermis is impervious to water because of presence of suberised matrix called
Casparian strip
The movement of water in endodermis is always _____
Symplastic
In young roots, xylem vessels and tracheids are a part of _____
Apoplast
A symbiotic association of root system with a fungus is called
Mycorrhiza
The part of fungus that absorbs mineral ions and water from soil is
Hyphae
In mycorrhiza, much larger volume of minerals and water are provided to the roots by
Fungus
Sugars and N-containing compounds are provided by ____ to mycorrhizae
Roots
Name a plant having obligate relationship with mycorrhizae
Pinus
Pinus seeds cannot germinate and establish without the presence of which association ?
Mycorrhizae
The positive pressure responsible for pushing up water to small heights in stem is called
Root pressure
Water loss from plants in liquid phase is called
Guttation
Majority of water transport occurs due to pressure generated in plants by _______
Transpiratory pull
Cohensin-tension-transpiration pull model states that the driving force for water movement is ____
Transpiration
The loss of water through stomata in leaves by evaporation is called
Transpiration
Transpiration mainly occurs through _____
Stomata
The opening and closing of sromata is due to change in tugidity of _____ cells
gaurd
Thickness and elasticity are characterised of which wall of gaurd cells?
Inner wall
Cellulose microfibrils are oreintated ____ rather than ______ making it easier for stoma to open
Radialy; longitudinal
During water stress, stoma closes because gaurd cells become _____
flaccid
The type of leaf exhibiting more number of stomata on lower side is called
Dorsiventral leaf
The leaf exhibitingequal number of stomata on both surfaces is called
Isobilateral leaf
Dorsiventral leaf is a characteristic feature of which plants?
Dicot plants
The leaf possessed by monocot planrs is
Isobilateral layer
Cohension, adhension and surface tension are the factors affecting
Transpiration pull
Mutual attraction between water molecules is called
Cohension
Adhension refers to the attraction of water molecules to
Polar surfaces
The phenomenon of water molecules getting attracted more to each other in liquid phase more than to water in gas phase is termed as
Surface tension
Cohension, adhension and surface tension provides ____ strength and capillarity to water
Higher tensile
Small diameters of tracheids and vessel elements provide high ____
Capillarity
Transpirationsl pull is created due to lower concentration of water vapour in ______
Atmosphere
The transpirational pull for absorption and transport in plants is created by _____
transpiration
Water for photosynthesis is supplied by the process of
Transiration
Evaporative cooling is due to?
Transpiration
The evolution of which photosynthetic system has maximised the availability of carbon dioxide minimising water loss?
C4 pathway
C4 plants are twice as efficient as C3 plants in terms of ____
CO2 fixation
The minerals which are present in lower concebtration in soil than roots are absorbed by
active transport
The process of osmosis keeps going due to water potential gradient in roots which is maintained due to?
Active uptake of ions
The quantity and type of solutes that reach xylem is regulated by transport proteins of which cells?
Endodermal cells
Root endodermis has ability to actively transport ions in one direction only due to the presence of _____
Suberin
After ions have reached xylem, further transport occurs through
Transpirational stream
Unloading of mineralions occur at the fine vein endings through __ and ___ uptake by growing regions of plant
diffusion and active
Structureal components like ___ are not remobilised before senescence
Calcium
Four most readily mobilised elements in plants are
phosphorous, sulphur, nitrogen and potassium
Most of the nitrogenin plants is transported in ____ form
organic
The vascular issue which transports sucrose in plants is _____
phloem
The direction of movement in phloem is
Bi-directional
The two main components of phloem sap are
Water and sucrose
Phloem sap is mainly water and sucrose, but other sugars, hormones and amino acids are transported or translocated through _____
Phloem
The accepted mechanism for translocation of sugars from source to sink is
Pressure flow hyphothesis
Glucose prepared by photosynthesis is converted into _____
sucrose
Hypertonic condition created in phloem leads to transport of water from adjacent xylem to phloem by the process of
Osmosis
The process of loading sucrose at sorce generate ______ condition in phloem
Hypertonic
The type of transport which mobilises sugars in plants is
Active transport
Phloem tissue is composed of ____, which form long columns with holes in their end walls
Sieve tube cells
The water from phloem returns to xylem due to loss of ___ in it
Solute
The expeiment which was used to identify the tissues through which food transport is _____
Gridling
Plants need to move molecules over very long diatances, much more than animals do; they alsodo not have a ____ system in place
Circulatory
Water taken up by the roots has to reach all parts of the plant, up to the very tip of the ____
growing stem
The _____ or food synthesised by the leaves have also to be moved to all parts including the root tips embedded deep inside the soil
photosynthesis
Movement across short distances, say within the _____, across the ___ and from ___ within the tissue has to take place
cell, membranes, cell to cell
What are the substances that would need to be transported in a flowering plant?
water, mineral nutrients, organic nutrients and plant growth regulators
Organic compounds synthesised in the photosynthetic leaves are exported to all other parts of the plant including ____
storage organs
From the storage organs the organic compounds are later _____
re-exported
The mineral nutrients are taken up by the roots and transported upwards into the _____, _____ and the _____
stem, leaves, growing regions
When any plant part undergoes ______, nutrients may be withdrawn from such regions and moved to the growing parts
senescence
______ or ______ and other ______ are also transported, through in very small amounts, sometimes in a strictly polarised or unidertional manner from where they are synthesised to other parts
Hormones, plant growth regulators, chemical signals
In a flowering plant there is a _____ traffic of compounds (but probably very ______ ) moving in different directions, each organ receiving some substances and giving out some others
complex, orderly
Movement by diffusion may be from one part of the cell to the other, or from ____ or over ____, say from the _____ spaces of the leaf to the outside
cell to cell, short distances, inter-cellular
In diffusion, no _____ expenditure takes place
energy
In diffusion,molecules move in a _____ fashion
random
The net result of diffusion is substances moving from regions of _____ concentration to regions of ____ concentration
higher, lower
Diffusion is a slow process and is not dependent on a ‘_____’
living system
Diffusion is obvious in ____ and ____
gases, liquids
_____ in solids is more likely rather than of solids
Diffusion
A ______ must already be present for diffusion to occur
gradient
The diffusion rate depends on the size of the substances; obviously ____ subatances diffuse faster
smaller
The diffusion of any substance across a membrane also depends on its solubility in _____, the major constituent of the membrane
lipids
Substances soluble in lipids diffuse through the membrane ____
faster
Substances that have a _____ moiety, find it difficult to pass through membrane; their movement has to be facilitated
hydrophilic
Membrane _____ provide site at which hydrophilic molecules across the membrane
proteins
Facilitated diffusion cannot cause net transport of molecules from a ____ to a ____ concentration
low, high
_______ reaches a maximum when all of the protein transporters are being used(saturation)
Transport rate
Facilitated diffusion allows cell to select substances for ____
uptake
The proteins form _____ in the membrane for molecules to pass through
channels
Some channels are always open; others can be ____
controlled
Some protein channels are _____, allowing a variety of molecules to cross
large
The porins are proteins that form large pores in the _____________ allowing molecules up to the size of small proteins to pass through
outer membranes of the plastids, mitochondria and some bacteria
The transport protein _____ and releases the molecule inside the cell, e.g., water channels
rotates
______ transport is carried out by specific membrane-proteins
Active
Different proteins in the membrane play a major role in both _____ as well as _____ transport
active, passive
_______ are proteins that use energy to carry substances across the cell membrane
pumps
Pumps can transport substances from a ____ concentration to a ____ concentartion (‘uphill transport’)
low, high
Transport rate reaches a _____ when all protein tansporters are being used or are saturated
maximum
Like _____ the carrier protein is very specific in what it carries across the membrane
enzymes
Proteins in the membrane are responsible for _____ and ____
facilitated diffusion, active transport
Protein transporters are liable to ____, respond to ___ and are under ___ regulation
saturate, inhibitors, hormonal
____ whether facilitated or not- take place only along a gradient and do not use energy
Diffusion
Water is essential for all _____ activities of the plant and plays a very important role in all living organisms
physiological
The _____ of the cells is nothing but water in which different molecules are dissolved and (several particles) suspended
protoplasm
A ____ has over 92 per cent water; most herbaceous plants have only about ____ percent of its fresh weight as dry matter
watermelon, 10 to 15
Distribution of water within a plant varies- _____ have relatively very little water, while ____ mostly contains water
woody parts, soft parts
A seed may appear dry but it still has water- otherwise it would not be _____ and ____
alive, respiring
Terrestrial plants take up huge amount water daily but most of it is lost to the air through _____ from the leaves
evaporation
A mature corn plant absorbs almost ____ litres of water in a day
three
A _____ plant absorbs water equal to its own weight in about 5 hours
mustard
Water is often the limiting factor for plant ____ and ____ in both agricultural and natural environments
growth, productivity
______ is a concept fundamental to understanding water movement
water potential
Water molecules possess ____ energy
kinetuc
In _____ and ____ form water molecules are in random motion that is both rapid and constant
liquid, gaseous
The greater the concentration of ___ in system, the greater is its kinetic energy or ‘water potential’
water
Random movement of water molecules in a close system will result in net movement of water molecules from system with ___ energy to the one with ____ energy
higher, lower
Water will move from the system containing water at ____ water potential to the one having ____ water potential
higher,low
This process of movement of substances down a gradient of _____ is called diffusion
free energy
Water potential is expressed in pressure units such as ____
pascals (Pa)
By convection, the water potential of pure water at standard temperatures, which is not under any pressure, is taken to be _____
zero
If some solute is dissolved in pure water, the solution has fewer free water molecules and the ____ of water decreases
concentration (free energy)
Solute potential is always _____
negative
The more the solute molecules, the ____ is the Ys
lower (more negative)
Pressure can build up in a plant system when water enters a plant cell due to diffusion causing a pressure built up against the _____
cell wall
A pressure build up against the cell wall makes the cell ____
turgid
Pressure potential is usually ____
positive
The plant cell is surrounded by a ____ and a cell wall
cell membrane
The cell wall is ____ to water and substances in solution hence is not a barrier to movement
freely permeable
In plant cells, what together are important determinants of movement of molecules in or out of the cell?
the cell membrane and the membrane of the vacuole, the tonoplast
Osmosis occurs ____ in responsible to a driving force
spontaneously
Water will move from its region of higher chemical potential (or concentration) to its region of lower chemical potential until ____ is reached
equilibrium
At equilibrium the two chambers should have nearly the same ____
water potential
The pressure required to prevent water from diffusing is in fact, the ___ and this is the function of the solute concentration
osmotic pressure
More the _____ greater will be the pressure required to prevent water from diffusing in
solute concentration
Osmotic pressure is the ____ pressure applied, while osmotic potential is ____
positive, negative
The behaviour of the plant cells (or tissues) with regard to water movement depends on the surrounding _______
solution
If the external solution is more concentrated than the cytoplasm, it is called
hypertonic
During plasmolysis, water is first lost from the _______________
Cytoplasm
Water moves out; it is first lost from the cytoplasm and then from the _______
vacuole
The water when drawn out of the cell through diffusion into the __________ fluid causes the protoplast to shrink away from the walls.
extracellular
During plasmolysis movement of water occurred across the membrane moving from an area of __________ to an area of ____________ outside the cell.
high water potential, lower water potential
If the _________ balances the _________ of the cytoplasm it is said to be isotonic.
external solution, osmotic pressure
The process of _________ is usually reversible.
plasmolysis
When the cells are placed in a _________ solution, water diffuses into the cell causing the cytoplasm to build up a pressure against the wall.
hypotonic
The pressure that is produced by the __________ had been used by prehistoric man to split rocks and boulders.
swelling of wood
If it were not for the pressure due to _______, seedlings would not have emerged from the soil into the open.
imbibition
The seeds and other such materials have almost no water hence they ________ water easily.
absorb
Water potential gradient between the ________ and the _______ is essential for imbibition.
absorbent, liquid imbibed
In addition, for any substance to imbibe any liquid, affinity between the adsorbant and the liquid is also a ___________.
pre-requisite
Long distance transport of substances within a plant cannot be by __________ alone.
diffusion
Diffusion is a slow process and can account for only ___________ movement of molecules.
short distance
The movement of a molecule across a typical plant cell (about 50 µm) takes approximately _______ seconds.
2.5
In ________ and ________ organisms, often substances have to be moved to long distances.
large, complex
Sometimes the sites of production or absorption and sites of storage are too far from each other; _______ or ___________ would not suffice.
diffusion, active transport
Special long distance transport systems become necessary so as to move substances across ___________ distances and at a much ______ rate.
long, faster
Mass flow is the movement of substances in bulk or en masse from one point to another as a result of _________ differences between the two points.
pressure
It is a characteristic of __________ that substances, whether in solution or in suspension, are swept along at the same pace, as in a flowing river.
mass flow
In diffusion, different substances move independently depending on their ________ gradients.
concentration
Give an example where positive hydrostatic pressure occurs.
a garden hose
Give an example where negative hydrostatic pressure occurs.
suction through a straw
The higher plants have highly specialised vascular tissues – _________
xylem and phloem.
Root hairs that are present in __________ at the tips of the roots.
millions
Once water is absorbed by the root hairs, it can move deeper into root layers by _____ distinct pathways.
two
The __________ does not provide any barrier to water movement.
apoplast
As water ________ into the intercellular spaces or the atmosphere, ________ develop in the continuous stream of water in the apoplast.
evaporates,tension
During symplastic movement, the water travels through the cells – their ________
cytoplasm
Neighbouring cells are connected through cytoplasmic strands that extend through __________
plasmodesmata
In which process, water absorbed by root hairs has to enter the cells through the cell membrane?
Symplastic pathway
Among apoplast and symplast, which of the two has faster water movement?
Apoplast pathway
In symplastic pathway, movement is again _______ a potential gradient.
down
In cells of the ________ leaf; the movement of chloroplast due to streaming is easily visible.
Hydrilla
The __________ cells are loosely packed, and hence offer no resistance to water movement.
cortical
Water molecules are unable to penetrate endodermis layer, so they are directed to wall regions that are not suberised, into the cells proper through the ___________.
membranes
The water then moves through the symplast and again crosses a membrane to reach the cells of the _________
xylem
Symplast is the ultimate way through which water and other solutes can enter the _______ cylinder
vascular
Once inside the xylem, __________ is again free to move between cells as well as through them.
water
Xylem vessels and/or tracheids are __________ conduits.
non-living
Some plants have additional structures associated with them that help in water (and mineral) __________.
absorption
The_______ filaments form a network around the young root or they penetrate the root cells.
fungal
As various ions from the soil are actively transported into the vascular tissues of the ________, water follows (its potential gradient) and increases the pressure inside the xylem.
roots
Effects of root pressure is also observable at night and early morning when ___________ is low
evaporation
Due to guttation excess water collects in the form of droplets around special openings of veins near the tip of ________, and leaves of many _________ parts.
grass blades, herbaceous
_________ can, at best, only provide a modest push in the overall process of water transport
Root pressure
Root pressure do not play a major role in water movement up ________.
tall trees
The greatest contribution of root pressure may be to ________ the continuous chains of water molecules in the xylem.
re-establish
Continuous chains of water molecules in the xylem often break under the enormous tensions created by __________.
transpiration
__________ does not account for the majority of water transport.
Root pressure
The upward flow of water through the xylem in plants can achieve fairly high rates, up to ________ per hour.
15 metres
Most researchers agree that water is mainly __________ through the plant
pulled
The driving force for the process of water movement in xylem is _________ from the leaves.
transpiration
Water is ________ in plants.
transient
Less than __________ of the water reaching the leaves is used in photosynthesis and plant growth.
1 percent
Water loss from a leaf can be studied ___________ paper, which turns colour on absorbing water.
cobalt chloride
Exchange of __________ and __________ in the leaf also occurs through these stomata.
oxygen, carbon dioxide
Normally stomata are open in the _______ and close during the _________.
day time, night
The immediate cause of the opening or closing of stomata is a change in the ________ of the guard cells
turgidity
The inner wall of each guard cell, towards the pore or ___________, is thick and elastic
stomatal aperture
When turgidity increases within the two guard cells, the thin outer walls bulge out and force the inner walls into a _______ shape.
crescent
The opening of the stoma is also aided due to the __________ of the microfibrils in the cell walls of the guard cells.
orientation
Cellulose microfibrils are oriented _______ rather than longitudinally
radially
The guard cells lose turgor, due to ____________.
water loss (or water stress)
When the guard cells lose turgor, the elastic __________ regain their original shape.
inner walls
Mention the external factors that affect transpiration.
temperature, light,humidity, wind speed
Mention the plant factors that affect transpiration.
number and distribution of stomata, percent of open stomata, water status of the plant, canopy structure, etc.
The transpiration driven ___________ depends mainly on the physical properties of water.
ascent of xylem sap
An ability to resist a pulling force in water is called _________.
tensile strength
The ability to rise in thin tubes is called __________.
capillarity
The system of ___________ from the root to the leaf vein can supply the needed water.
xylem vessels
As water evaporates through the stomata, since the thin film of water over the cells is _____________, it results in ________ of water, molecule by molecule, into the leaf from the xylem.
continuous, pulling
Because of lower concentration of water vapour in the atmosphere as compared to the _____________ and ______________, water diffuses into the surrounding air.
substomatal cavity, intercellular spaces
Measurements reveal that the forces generated by transpiration can create pressures sufficient to lift a xylem sized column of water over _______ high.
130 metres
Transpiration cools leaf surfaces, sometimes ___________, by evaporative cooling
10 to 15 degrees
Transpiration maintains the ____________ of the plants by keeping cells turgid
shape and structure
An actively photosynthesising plant has an insatiable need for ________.
water
__________ is limited by available water which can be swiftly depleted by transpiration.
Photosynthesis
The humidity of __________ is largely due to this vast cycling of water from root to leaf to atmosphere and back to the soil
rainforests
A C4 plant loses only half as much ____ as a C3 plant for the same amount of CO2 fixed.
water
Plants obtain their carbon and most of their oxygen from ______ in the atmosphere.
CO2
Plant’s remaining nutritional requirements are obtained from _________ and _______in the soil.
water, minerals
Unlike _______, all minerals cannot be passively absorbed by the roots
water
Minerals are present in the soil as __________ which cannot move across cell membranes
charged particles (ions)
The concentration of minerals in the _____ is usually lower than the concentration of minerals in the ______.
soil, root
In roots, active absorption into the cytoplasm of epidermal cells needs energy in the form of _____.
ATP
The active uptake of ions is partly responsible for the __________ in roots
water potential gradient
Some ions also move into the epidermal cells __________
passively
__________ are absorbed from the soil by both passive and active transport
Ions
Specific proteins in the membranes of root hair cells actively pump ions from the soil into the __________ of the epidermal cells
cytoplasms
The endodermal cells have many ___________ embedded in their plasma membrane; they let some solutes cross the membrane, but not others
transport proteins
Mention the chief sinks for the mineral elements in plants.
The growing regions of the plant, such as the apical and lateral meristems, young leaves, developing flowers, fruits and seeds, and the storage organs
Unloading of mineral ions occurs at the fine vein endings through ______ and active uptake by these cells
diffusion
Mineral ions are frequently remobilised, particularly from __________, _______ parts.
older, senescing
Older dying leaves export much of their mineral content to ________.
younger leaves
Before leaf fall in decidous plants, ________ are removed to other parts.
minerals
An analysis of the xylem exudates shows that though some of the nitrogen travels as inorganic ions, much of it is carried in the organic form as __________ and related compounds.
amino acids
Small amounts of P and S are carried as ________ compounds
organic
In addition, small amount of exchange of materials does take place between _______ and ______.
xylem, phloem
Hence, it is not that we can clearly make a distinction and say categorically that xylem transports only _________ while phloem transports only ___________, as was traditionally believed.
inorganic nutrients, organic materials
Food, primarily ________, is transported by the vascular tissue phloem from a source to a sink.
sucrose
Usually the source is understood to be that part of the plant which ___________ the food, i.e., the leaf
synthesises
Part of the plant that needs or stores the food is called _________
sink
The source and sink may be ___________ depending on the season, or the plant’s needs.
reversed
Sugar stored in roots may be mobilised to become a source of food in the early _______.
spring
In the early spring the ________ of trees, act as sink; they need energy for growth and development of the photosynthetic apparatus
buds
Since the __________ relationship is variable, the direction of movement in the phloem can be upwards or downwards, i.e., bi-directional.
source-sink
In the _________ the movement is always unidirectional, i.e., upwards.
xylem
Unlike one-way flow of water in transpiration, food in phloem sap can be transported in any required direction so long as there is a source of sugar and a sink able to ___________ the sugar.
use, store or remove
The sugar is then moved in the form of sucrose into the ___________ and then into the living phloem _________ cells by active transport.
companion cells, sieve tube
As ___________ pressure builds up the phloem sap will move to areas of lower pressure.
osmotic
At the ________ osmotic pressure must be reduced.
sink
The cells which use the sugar –convert it into __________, ___________ or ___________.
energy, starch, cellulose
As sugars are removed, the osmotic pressure decreases and ______ moves out of the phloem
water
The movement of sugars in the phloem begins at the ________, where sugars are loaded (actively transported) into a sieve tube.
source
__________ of the phloem sets up a water potential gradient
Loading
Cytoplasmic strands pass through the holes in the __________, so forming continuous filaments
sieve plates
As ___________ pressure in the sieve tube of phloem increases, pressure flow begins, and the sap moves through the phloem.
hydrostatic
At the sink, incoming sugars are actively transported out of the phloem as complex __________
carbohydrates
The loss of solute produces a high water potential in the ________, and water passes out, returning eventually to xylem.
phloem
On the trunk of a tree a ring of bark up to a depth of the ________ layer, can be carefully removed.
phloem
In girdling, due to the absence of _________ movement of food the portion of the bark above the ring on the stem becomes swollen after a few weeks.
downward
