XI Chap 11 Transport in Plants Flashcards
___________ won the Nobel Prize in 1961 for mapping of the pathway of carbon assimilation in photosynthesis
Melvin Calvin
Principles of photosynthesis as established by Melvin Calvin are being used in studies on ______________
renewable resources
Plants are much smaller than animals and hence do not need to move molecules over very long distances. T or F?
False, they have to move them over very long distances.
Plants have a circulatory system to transport nutrients and water. T or F?
False, They do not have circulatory system.
Photosynthates are ________
food synthesized by plant leaves
In a flowering plant, what substances need to be transported?
water
mineral nutrients
organic nutrients
plant growth regulators
Over small distances, substances in plants move by _______, ______ and _________
diffusion, cytoplasmic streaming and active transport
Over long distances, substances are transported through __________
vascular system (xylem and phloem)
What is translocation?
Bulk movement of substances
conducting/vascular tissues
long distances
in plants
In rooted plants, transport of ___________ is unidirectional and of ____________ is multidirectional
water and minerals - unidirectional
organic and mineral nutrients - multidirectional
How are hormones or growth regulators transported?
very small amounts,
sometimes in strictly polarised or unidirectional manner
Movement by diffusion is active or passive?
Slow or fast?
Energy requiring or not?
Passive, slow, no energy expenditure
Diffusion is dependent on living system. T or F?
False
Diffusion ___ solids is more likely rather than ___ solids
in solids more likely than of
_______ is the only means for gaseous movement within the plant body
Diffusion
A ________ must already be present for diffusion
gradient
Smaller substances diffuse fast or slow?
Fast
Diffusion across a membrane depends on _________
solubility in lipids, soluble => diffuse faster
Substances that have a ________ find it difficult to pass through membrane
hydrophilic moeity
What is facilitated diffusion
membrane proteins provide sites for hydrophilic molecules to cross the membrane
Facilitated diffusion occurs against the gradient. T or F?
False, occurs along the gradient, just at specific sites
Facilitated diffusion requires ATP. T or F?
False
When does transport rate reach maximum in facilitated diffusion?
When all of protein transporters are being used (saturation)
Facilitated diffusion is non-specific. T or F?
very specific, only allows select substances for uptake
Why is facilitated diffusion sensitive to inhibitors?
They react with protein side chains
Proteins form ____ in the membrane for molecules to pass through in facilitated diffusion
channels
Protein channels can be open or ______
controlled
A porin is ______
a protein that forms large pores in outer membrane of plastids, mitochondria and some bacteria allowing molecules up to the size of small proteins to pass through
Transport/carrier protein rotates to transport a molecule from the outside to the inside. T or F?
True
Water protein channels are made up of ___ different types of _______
8, aquaporins
What are the 3 types of transport proteins?
- Symport - 2 types of molecules move together (same direction)
- Antiport - 2 types of molecules move in opp. directions
- Uniport - one molecule moves across
What is active transport?
against a concentration gradient (low to high / uphill), requires energy
What are pumps?
Proteins that use energy to carry substances across membrane (uphill)
Like enzymes, carrier proteins are very specific. T or F?
True
What’s common and what’s different in
Simple vs Facilitated diffusion?
Common: along gradient so
- downhill transport
- does not require ATP
Simple diffusion - no proteins, not selective, no transport saturation (all true for facilitated)
What’s common and what’s different in
Active transport vs Facilitated diffusion?
Common: both use proteins hence
- highly selective
- transport saturates
- respond to inhibitors
- under hormonal regulation
Active transport - uphill transport, energy required
_______ is essential for all physiological activities of the plant
Water
______ provides the medium in which most substances in living organisms are dissolved.
Water
Protoplasm of the cells is nothing by _____
water
Watermelon has over _____% water
92%
Most herbaceous plants have only about _______ percent of its fresh weight as dry matter
10-15%
Woody parts have the most water in plants. T or F?
False, woody parts - very little water,
soft parts - water
Seed is dry i.e. it does not contain water. T or F?
False, it still has water even though dry
_________ plants take up a huge amount of water but most of it is lost to the air through process called ___________
Terrestrial plants, transpiration
In transpiration, plants lose water through evaporation from _______
the leaves
A mature corn plant absorbs _____ litres of water in a day
3 L
Mustard plant absorbs how much water?
equal to its own weight in 5 hours
__________ is often the limiting factor for plant growth and productivity in both agricultural and natural environments
Water
_______ and _______ are the two main components that determine water potential.
Solute potential and pressure potential
Water molecules possess _________ energy
Kinetic
In liquid and gaseous form, water molecules are in _________ motion that is both ______ and _______
random, rapid, constant
Greater the concentration of water in a system, the greater is its ________ or _________
kinetic energy or water potential
Pure water will have the lowest water potential. T or F?
False, highest
Water moves from system containing _____ water potential to _______. This is aka ________
higher; lower
diffusion
Water potential is denoted by the Greek symbol _____
Psi Ψ
Water potential is expressed in units such as _______
pascals (Pa)
Water potential of pure water at standard temperatures which is not under any pressure is taken to be _____
zero
How does solute reduce water potential?
Dissolved => solution has fewer free water molecules => free energy/concentration of water decreases
All solutions have higher water potential than lower water. T or F?
False, lower
Ψs (solute potential) is always ___________
negative
Solution at atmospheric pressure, what is the relation between Ψw and Ψs
Ψw = Ψs
At atmospheric pressure, Ψp is _____
0
If a pressure greater than atmospheric pressure is applied, Ψw decreases or increases?
increases
Pumping water from one place to another is an example of ___________
increasing pressure => water potential increases
When water enters a plant cell by diffusion, ________ is built up against the cell wall and makes the cell _________. One can say pressure potential in this cell has ________
pressure, turgid;
increased
Pressure potential is positive or negative?
Solute potential is positive of negative?
Pressure - usually positive (can be negative in plant xylem)
solute - negative
Relationship between Ψs Ψw Ψp
Ψw = Ψs + Ψp
Cell wall is freely permeable to water and substances in solution. T or F?
True
In plant cells, ____________ contributes to the solute potential of the cell
vacuolar sap
Which two membranes determine movement of molecules in or out of the cell?
Cell membrane
Vacuole membrane i.e. tonoplast
Osmosis specifically refers to the diffusion of ________
water
Osmosis occurs spontaneously in response to a ______________
driving force
The net direction and rate of osmosis depends on both _____ gradient and ______ gradient
pressure and concentration
Water moves from region of ______ chemical potential to _____ chemical potential
higher to lower
_________ is the pressure required to prevent water from diffusion into a solution.
Osmotic pressure
The more the solute concentration, the _______ the osmotic pressure has to be
greater
Osmotic pressure is equal to osmotic potential. T or F?
False, numerically equivalent but signs are opposite
positive osmotic pressure => osmotic potential is negative
Isotonic vs. hypotonic vs. hypertonic?
Isotonic - external solution balances osmotic pressure of cytoplasm
Hypotonic - external solution dilute
Hypertonic - external solution more concentrated
How do cells react in hypotonic vs hypertonic solutions?
Hypotonic - water enters, cell swells, cytoplasm builds pressure against wall, turgid
Hypertonic - water leaves (cytoplasm then vacuole), protoplast shrinks away from walls, “plasmolysed”
How do cells react in isotonic solution?
no net flow of water, cells are flaccid
Process of plasmolysis is irreversible. T or F?
False, reversible
What is turgor pressure?
When cytoplasm builds up pressure against cell wall due to water diffusing into the cell (hypotonic solution)
Why does cell not rupture in a hypotonic solution?
due to rigidity of cell wall
Pressure exerted by the protoplasts against rigid cell walls due to entry of water is called _______________
pressure potential Ψp
___________ is ultimately responsible for enlargement and extension growth of cells
Turgor pressure
___________ is a special type of diffusion where water is absorbed by solids / colloids
Imbibition
What are the classical examples of imbibition?
Seeds and dry wood
Pressure produced by swelling of wood due to water has been used by prehistoric man to ____________
split rocks and boulders
Imbibition is also diffusion. True or False? Explain.
True, since water movement is along a concentration gradient
In imbibition, in addition to water potential gradient, affinity between _____ and _____ is a pre-requisite.
adsorbant and liquid
Typical plant cell size
50μm
Movement of a molecule across a typical plant cell (50 μm) takes how long?
2.5 seconds
At typical rate of movement of molecule in plant cell, how long would it take for movement of molecules over distance of 1m by diffusion along?
2 years
Water and minerals, and food are generally moved in plants by a _______ system
mass / bulk flow system
_________ is the movement of substances in bulk or en masse as a result of ________ differences between 2 points
Mass flow, pressure differences
In mass flow, different substances are swept along at different paces like in diffusion. T or F?
False,
like flowing river - same pace for all substances in mass flow;
in diffusion, different paces depending on gradients
Bulk flow can be achieved through _______ or ________ gradients. Give examples.
positive hydrostatic pressure gradient (garden hose) or
negative hydrostatic pressure gradient (suction through straw)
_____ plants have highly specialized vascular tissues
Higher plants
Xylem is associated with the translocation of ________________ from roots to the aerial parts of plants.
mainly water, mineral salts;
some organic nitrogen and hormones
Phloem translocates a variety of organic solutes (but not inorganic) mainly from the leaves to other parts of the plant. T or F?
False, organic and inorganic solutes
Responsibility of absorption of water and minerals is the function of ________
root hairs
How many root hairs typically in root tips of plant?
Millions
What are root hairs?
Thin-walled slender extensions of root epidermal cells
Root hairs increase ______________ for absorption
surface area
Water + mineral solutes are absorbed by root hairs by process of ________
diffusion
Two pathways for water in roots?
Apoplast and symplast
Apoplast is a system of __________ while symplast is a system of __________
apoplast - adjacent cell walls
symplast - interconnected protoplasts
Continuous layer of cell walls throughout the plant is broken by _______
casparian strips of endodermis
Movement across apoplast involves intercellular spaces, walls of the cells, and across the cell membrane. T or F?
False, first two correct. does NOT cross cell membrane
Apoplast movement is dependent on _________
gradient
Apoplast does not provide any barrier to water movement and movement is through mass flow. T or F?
True
Why does mass flow of water occur in apoplast pathway?
Adhesive and cohesive properties of water, and tension developed in continuous stream of water as water evaporates into intercellular spaces or atmosphere
In symplast pathway, neighboring cells are connected through ____________ that extend through the _________
cytoplasmic strands, plasmodesmata
In symplastic movement, water travels within cells through _______ and across cells through ________
cytoplasm, plasmodesmata
Water movement is faster or slower in symplastic system? Why?
Slower, because it has to enter through cell membrane
Water movement in apoplast and symplast pathways are along a gradient. T or F?
True
Symplastic movement is aided by ____________
cytoplasmic streaming
Movement of chloroplast in cells of Hydrilla leaf is an example of?
Cytoplasmic streaming
Most of water flow in roots occurs via _________
apoplast
Most of water flow in roots occurs through apoplast since …?
cortical cells are loosely packed and hence no resistance to water movement
The inner boundary of the cortex called the _________ is impervious to water because of ____________
endodermis, casparian strip (band of suberised matrix)
At the endodermis, water moves through ______ (apoplast/symplast) and crosses a membrane again to reach ______
symplast, xylem
Water movement in the root layers in the epidermis is ultimately ________
symplastic
Once inside the xylem, water is free to move apoplastically or symplastically?
Both
In young roots, water enters directly into _______, which are non-living conduits and so are part of the _________
xylem vessels and/or tracheids, apoplast
________ is a symbiotic association between fungus and root system
Mycorrhiza
Fungal filaments in mycorrhiza form a ______ around the young root or they ________
network; penetrate root cells
Hypae have a very large ________ in mycorrhiza that absorb ______ and _____ from soil, much better than roots can
surface area, water and mineral ions
In mycorrhiza, plants provide _______ and ______ to fungus.
sugars, N-containing compounds
Some plants have an obligate association with the mycorrhizae. T or F?
True
Pinus seeds cannot germinate and establish without the presence of __________
mycorrhizae
Water movement into roots is active or passive?
Passive
What is root pressure?
Water follows pressure gradient and increases pressure inside the xylem
__________ is responsible for pushing up water to small heights in the stem
Root pressure
Effects of root pressure are observable at night and early morning when _______ is low; excess water collects in form of droplets around ___________ near tips of leaves / grass blades.
evaporation; special openings of veins
What is guttation?
Water loss in liquid phase due to root pressure, visible at night / early morning when evaporation is low
Root pressure places a major role in upwards water movement in tall trees as evidenced by guttation. T or F?
False, only modest role, transpiratory pull required for major upwards movement
Greatest contribution of root pressure is ________
re-establish continuous chains of water molecules in xylem which break due to transpiration
Upwards movement of water in plants can go as fast as _________
15 meters per hour
Water is mainly ‘pulled’ through plant, driving force being transpiration from leaves. What is this model of water transport called?
Cohesion-tension-transpiration pull model
Less than ______ of the water reaching leaves is used in photosynthesis. Most of it is lost through ____ in the leaves
1%
stomata
What is transpiration?
evaporative loss of water through stomata
Besides transpiration, exchange of _____ and ______ in leaf also occurs through stomata
oxygen and carbon dioxide
Normally stomata are open in the ______ and closed in the ______
day; night
Immediate cause of opening or closing of stomata is a change in __________
turgidity of the guard cells
Inner wall of each guard cell, towards the pore, is _____ and ______
thick and elastic
When turgidity (increases / decreases) in flanking guard cells, think outer walls _______ and force the _______ into a crescent shape
increases,
bulge out,
inner walls
How many guard cells flank stomata?
2
Opening of stomata is aided due to the orientation of ____________ in the cell walls of the guard cells. Cellulose microfibrils are oriented ________ rather than ________.
microfibrils,
radially rather than longitudinally
When turgidity (increases / decreases) in flanking guard cells due to _________, elastic inner walls regain original shape, guard cells become _____ and stoma closes.
decreases,
water stress / loss,
flaccid
Lower surface of a monocot leaf has greater number of stomata. T or F?
False, dicot leaf
Dorsiventral leaf has greater number of stomata in ______ while isobilateral leaf has ________
lower surface, equal on both surfaces
Transpiration is affected by what internal (plant) factors
number and distribution of stomata,
percent of open stomata,
water status of plant,
canopy structure
Transpiration is affected by what external factors
temperature,
light,
humidity,
wind speed
Transpiration driven ascent of xylem sap depends mainly on what properties of water?
Cohesion, Adhesion and Surface tension
What is cohesion property of water?
mutual attraction between water molecules
What is adhesion property of water?
attraction of water molecules to polar surfaces
What is surface tension property of water?
water molecules are attracted to each other in the liquid phase more than gas phase
Cohesion, Adhesion and Surface tension give water high __________ and high ______
tensile strength, capillarity
Tensile strength and Capillarity are?
tensile strength - ability to resist a pulling force,
capillarity - ability to rise in tubes
In plants, _______ is aided by the small diameter of tracheids and vessel elements,
capillary or tensile strength?
Capillary
Forces generated by transpiration can create pressures sufficient to lift a xylem sized column of water over _______ meters high
130
Five functions of transpiration?
- creates pull for absorption and transport
- supplies water for photosynthesis
- transports minerals from soil to all parts of plant
- cools leaf surfaces
- maintains the shape an structure of plants (cells kept turgid)
Evaporative cooling due to transpiration cools leaf surfaces by how many degrees?
10-15 degrees
Evolution of ___ photosynthetic system is a strategy to maximize the availability of ____ while minimizing loss of _____
C4, CO2, water
C4 plants are _____ as efficient as C3 in fixing CO2 and loses only ______ as much water as C3 plant for same amount of CO2 fixed.
twice as efficient,
halve as much water
Plants obtain their carbon and most of their oxygen from _____ in the atmosphere
CO2
All minerals can be passively absorbed by roots. T or F? Explain.
False, not all
- charged ions cannot move across cell membranes
- concentration in soil is lower than in roots
Most minerals enter the root through what process? Does it require energy?
Active absorption. Yes.
Active uptake of ions is partly responsible for the _______ gradient in roots, and therefore also responsible for ______
water potential gradient,
osmosis
Mineral ions are absorbed from soil by both passive and active transport. T or F?
True
Unlike all cells, endodermal cells have many transport proteins embedded in plasma membrane. T or F?
False, LIKE all cells, rest is correct
Transport proteins of endodermal cells are ________ where a plant adjusts the quantity and types of solutes that reach xylem.
control points
Root endodermis because of the layer of _____ has the ability to actively transport ions in _____ direction(s) (how many?)
suberin, one direction only
Chief sinks for the mineral elements are _________
growing regions of plant - apical and lateral meristems, young leaves, developing fruits/flowers/seeds and storage organs
Unloading of mineral ions at sinks occurs at the ________ through ____ and ____ processes
fine vein endings;
through diffusion and active transport
Mineral ions are frequently remobilized from older to younger parts of the plants. T or F?
True
Mineral ions, like calcium, are frequently remobilized from older to younger parts of the plants. T or F?
False, structural components like calcium are not remobilised
Before leaf fall in deciduous plants, minerals like ____________ (4) are moved to other parts.
phosphorus, sulphur, nitrogen and potassium
Some of the nitrogen travels as ____, most of it is carried in form of ______
some - inorganic ions,
most - organic form, amino acids and related compounds
Small amounts of ____ and ____ are carried as organic compounds
phosphorus and sulphur
No exchange of materials takes places between xylem and phloem as they are two separate transport systems. T or F?
False, small exchange does take place
Xylem only transports inorganic nutrients while phloem transports only organic. T or F?
False, small exchange takes place.
Food in plants is transported by phloem from _____ to ______
source to sink
Source and sink may be reversed depending on season or plants needs. T or F?
True
In early spring, ___ acts as sink and ___ as a source.
buds of trees - sink
roots - source
Direction of movement in the phloem and xylem?
Phloem - can be upwards or downwards i.e. bidirectional
Xylem - upwards only i.e. unidirectional
Phloem sap mainly constitutes _____ and _____, but other substances like _____, _____ and ______ are also translocated
water and sucrose;
sugars, hormones, amino acids
What is the pressure flow hypothesis?
Accepted mechanism for translocation of sugars.
Sugar (sucrose) prepared at source -> moved into companion cells -> living phloem sieve tube cells (active transport) -> hypertonic condition in the phloem -> osmosis from adjacent xylem into phloem -> osmotic/hydrostatic pressure pressure builds up in the phloem -> sap moves up and into the cells that use the sugar
Sugars are converted in to ____ by plant cells that use it
energy, starch or cellulose
As sugar is unloaded from phloem, the osmotic pressure _______ (increases/decreases) and water moves ______ (into/out of) phloem
decreases, out of
Food is actively transported in the phloem. T or F?
True
Loading of phloem sets up a _______ potential gradient that facilitates mass movement in phloem
water
Phloem tissue is composed of _____ which form long columns with holes in their end walls called ______
sieve tubes, sieve plates
_________ pass through the holes in the sieve plates forming continuous filaments
Cytoplasmic strands
Incoming sugars are ________ (actively/passively) transported out of the phloem and removed as __________
actively, complex carbohydrates
When sugars leave sieve tubes at sinks, water follows by ________
osmosis
When sugar enters sieve tubes at source, water follows by osmosis and creates high _______ pressure
turgor
Sugar solution in phloem flows from regions of ______ turgor pressure to _______ turgor pressure
high to low
In the root, sugars leave sieve tube for _____ and ______
metabolism and storage
A simple experiment called _______ was used to identify the tissue through which food is transported and to show that transport takes place only in one direction.
girdling
Explain girdling
On tree trunk, remove ring up bark up to a depth of phloem layer. Downward movement of food cannot happen beyond that point, stem above ring becomes swollen after few weeks.
Plants obtain a variety of inorganic elements and salt from _____ and ______
water and soil
Passive transport is always entropy driven. T or F?
True
Diffusion of substances depends on two factors
- size
2. solubility in water / organic solvents
Osmosis depends on ____ and _____ gradient
pressure and concentration
Excess water is removed through tips of leaves of plants by ________
guttation
The source-sink relationship is variable. T or F?
True
