Lecture 4. PLANT-WATER RELATIONS Flashcards
(125 cards)
1
Q
Unique characteristics of water
an excellent solvent
A
Polarity of the molecule H2O
2
Q
Unique characteristics of water
which makes it capable of moving through plant tissues by capillary action
A
Viscosity
3
Q
Unique characteristics of water
which makes it capable of cooling plant tissues
A
Thermal properties
4
Q
Well-watered plants keep their shape because of the internal pressure of water in the cells, called
________.
A
turgor pressure
5
Q
This pressure is essential for plant cell
expansion, which leads to plant growth.
A
turgor pressure
6
Q
When there is insufficient water, the turgor pressure drops and causes the plant to _____.
A
wilt
7
Q
_____ absorb water from the soil, which is then carried through the plant.
A
Roots
8
Q
_____ is a solvent that moves minerals from the soil up through the plant.
A
Water
9
Q
movement of atoms or molecules from an area of high concentration to an area of low concentration.
A
Diffusion
10
Q
this movement results from the random
movement of molecules, ions or colloidal
particles caused by their own kinetic
energy.
A
Diffusion
11
Q
Movement of molecules from high concentration to low concentration; both solute and solvent move.
A
Diffusion
12
Q
Movement of solvent (water) across a semipermeable membrane from high to low solvent concentration; only solvent moves.
A
Osmosis
13
Q
power of a moving body to accomplish
work. At temperature above absolute zero (0 K or
273 C), all components of matter are in motion.
A
Kinetic energy
14
Q
_____ offers the least resistant to diffusing molecules because at normal temperature and pressure they are widely separated, thus limiting the number of collisions that would interfere with the diffusion of one gas into another.
A
Gas
15
Q
a hypothetical term describing the potential ability of a gas, liquid or solid to diffuse from an area of its greatest concentration to an area of lesser
concentration.
A
Diffusion pressure
16
Q
the direction of diffusion of a substance is determined entirely by the differences in diffusion pressure of the substance and is completely independent of the diffusion pressure of surrounding substances.
A
Independent diffusion
17
Q
Factors affecting rate of diffusion (of gases)
A
- Temperature
- Density of diffusing molecules
- Medium in which diffusion occurs
- Diffusion pressure gradient
- Size of diffusing molecule
- Solubility of diffusing molecule
18
Q
Special type of diffusion which is actually the
movement of water through a differentially
permeable membrane from an area of high
concentration to an area of low concentration.
A
Osmosis
19
Q
T or F
Osmosis will stop once forces controlling movement of water into tube balance those that controls water out of the tube.
A
True
20
Q
Parameters of Plant-Water Relations
A
1) Osmotic pressure
2) Turgor Pressure (TP)
3) Diffusion Pressure Deficit (DPD)
21
Q
can be measured indirectly; pressure needed to prevent the passage of pure water into an aqueous solution through a differentially-permeable membrane, thereby preventing an increase in the volume of the solution.
A
Osmotic pressure
22
Q
Cell membrane of plant cells are enclosed by a rigid relatively inelastic cell wall thus they can exist in a relatively wide range of osmotic concentrations in contrast with animal cell that can exist only in solution where osmotic concentration is equal to its own cell contents.
A
Turgor Pressure (TP)
23
Q
A
24
Q
actual pressure responsible for pushing the cell membrane against the cell wall.
A
TP
25
wall pressure being exerted by the rigid cell wall, in this condition
WP
26
plant cell is turgid
TP=WP
27
solution with OP greater than OP of cell sap -> loss of turgor, shrinking of vacuole, pulling away of the cell membrane from the cell wall implying the cell has been plasmolyzed
Hypertonic
28
solution with OP equal to OP of the plant cell
sap –> plant cell normal
Isotonic
29
solution with OP lesser than OP of plant cell sap; water will enter the cell causing more turgidity
Hypotonic
30
water potential difference in pressure
between a solution and pure water solvent when
both are subjected to the same atmospheric
pressure (same temperature)
Diffusion Pressure Deficit (DPD)
31
if both is subjected to the same pressure, the difference in pressure between the 2 is equal to the _____ of the solution.
OP
32
DPD = OP-TP
TP=0
DPD=OP
Cell is dry
33
DPD=0
TP=OP
Cell is turgid
34
process whereby the water from the cytoplasm of
cells is removed causing the cytoplasm to shrink
Plasmolysis
35
Measurement of OP
Measure of any of the colligative properties of solutions:
a. boiling point
b. freezing point depression (used to measure OP)
c. vapor pressure
36
The method making use of freezing point in determining the OP is called _________.
cryoscopic method
37
special type of diffusion; net movement of water is along a diffusion gradient
Imbibition
38
type of diffusion occurring between a liquid substance causing a recognizable change in the volume of the latter
Imbibition
39
Imbibition
a) Initial stage of water absorption by the roots
b) Initiate seed germination
c) Adhering water to the walls of xylem elements
d) Helps fruits to retain water
e) Plays a major role in young and actively growing tissues
40
analogous to OP in the sense that it represents the potential maximum pressure developed by the imbibant if submerged in pure water (Meyer, 1938).
Imbibition pressure (IP)
41
IP – TP
DPD
42
IP if imbibant is placed in an unconfined condition
DPD
43
Factors affecting rate and extent of imbibition:
1) Temperature
2) OP of substance to be imbibed affects amount and rate of water diffusion
44
Volume of whole system decreases after imbibition because water molecules are ______ tightly and as such are packed closer together.
adsorbed
45
binding of molecules or particles to a surface
Adsorption
46
filling of pores in a solid
Absorption
47
the release of an adsorbed substance from a surface
Desorption
48
Process whereby water is lost in the form of vapor through the leaves. Only 5% water vapor is utilized. Ninety five percent (95%) is lost in the form of vapor through transpiration.
TRANSPIRATION
49
Three types of transpiration:
1) Stomatal
2) Cuticular
3) Lenticular/epidermal
50
transpiration occurring in the stomata of the leaf
Stomatal transpiration
51
loss of water from the cuticle of the leaves, fruits and stem
Cuticular transpiration
52
loss of water through a pore-like structure (lenticels) found in the branches or stem; slow
Lenticular/epidermal transpiration
53
An acre of corn can transpire up to _________ gallons of water per day
3 ~ 4,000
54
A large tree can
transpire _____ gallons of water per year.
40,000
55
Methods of Measuring Transpiration
1. Gravimetric method
2. Potometer method
3. Cobalt-chloride method
4. Box method
5. Gas Exchange
56
Lysimeter
Gravimetric method
57
Stem-flow method
Potometer method
58
Cuvette Method
Gas Exchange
59
Involves loss of weight of plant from one period of time to another surface of soil covered so as to eliminate water loss due to evaporation.
Gravimetric method
60
Bubble is introduced in the capillary
Assumption: amount of water loss is the same as the amount of water absorbed
Potometer method
61
Specially prepared filter paper coated with cobalt-chloride is used, placed and pressed over a transpiring leaf blade, when not saturated it is colored blue, when saturated colored pink – time it takes to change color is compared to a given table to give the rate of water loss.
Cobalt-chloride method
62
Plant is enclosed in a box, CaCl2 is used, oven-dried first then weighed, placed inside U-tube, blow in air into box for plant to transpire. The pump will aid CaCl2 to absorb the water transpired.
Box method
63
# T or F
Movement of stomata is dependent upon the turgidity of the guard cells.
True
64
Guard cells are turgid.
Stomata opening
65
Guard cells are flaccid.
Stomata closing
66
Thinner wall expands _____ than thicker wall so pore will open.
more
67
Factors affecting stomatal movement:
1. Light
2. Water
3. Air temperature
68
Factors affecting rate of transpiration:
1) Plant factors
a) Root-shoot ratio
b.) Leaf area
c) Leaf structure
d) Leaf orientation
2) Environmental factors
a) Light
b) humidity of air
c) Temperature
d) Wind
e) Availability of soil water
69
Significance of transpiration:
1. Cooling effect
2. Effect on growth and development
3. Effect of mineral salt absorption
70
# Anatomy of xylem tissue
Xylem tissue cell types and functions
1. Tracheary elements (tracheids and vessels)
1. Xylem fibers
1. Xylem parenchyma
71
# Anatomy of xylem tissue
restricted to **angiosperms** only
Vessel or xylem duct
72
# Anatomy of xylem tissue
- found in all types of vascular plants;
- form the principal pathway in gymnosperms because vessels are not present;
- long spindle-shaped cells with sharply inclined end walls
Tracheids
73
# Anatomy of xylem tissue
Transports water and minerals through vessel elements and tracheids, which are dead at maturity and have a primary and secondary cell wall. In pits, the secondary wall is thin or missing, allowing water to flow laterally.
Xylem
74
# Anatomy of xylem tissue
--___ are for lateral movement of water; occur in pairs called ______ (may occur between two vessels, two tracheids, tracheids and vessels, living parenchyma cell).
Pits, pit pairs
75
- Dead at maturity
- Function for support
- Water translocation through fibers is uncertain
Xylem fibers
76
- Components of xylem rays called wood and ray parenchyma
- Function as storage
- Xylem ray parenchyma facilitates lateral distribution of water and nutrients
Xylem parenchyma
77
# Absorption of Water by Plants
Water is absorbed most in the _____, it diffuses into the root hair as a result of DPD gradient (DPD of cell sap greater than soil, water will move into the cell).
root hair zone
78
# Absorption of Water by Plants
Increase in solute concentration of cell or decrease in TP will _____ DPD
increase
79
# Absorption of Water by Plants
- lack cuticle and provide a large surface area
- extensions of the epidermal cells
- have sticky walls by whicht hey adhere tightly to soil particles
- extremely thin and large in number, thus provide
enormous surface area for absorption
- take in water from the intervening spaces mainly
by osmosis
Root hairs
80
# Absorption of Water by Plants
Water in the roots move by two pathways.
They can be classified as:
1) Apoplast pathway
2) Symplast pathway
81
# Absorption of Water by Plants
- the movement of water occurs exclusively through cell wall without the involvement of any membranes.
- majority of the amount of water goes through this pathway.
Apoplast pathway
82
# Absorption of Water by Plants
movement of water molecules is from cell to cell through the plasmodesmata.
Symplast pathway
83
# Absorption of Water by Plants
The ________ forms a network of cytoplasm of all cells.
plasmodesmata
84
- separates the cortex and the endodermis
- composed of a wax like substance called suberin, which blocks water and solute molecules through the cell wall of the endodermis
- water is forced to go through the cell membranes of different cells leading to a transmembrane pathway
Casparian strips
85
Mechanism of water absorption
1. Passive
2. Active
86
- Rapidly transpiring plant vessels and tracheids are generally in state of negative tension or reduced pressure
- At situation where transpiration exceeds absorption a suction force is produced by the moving columns of water literally pulling water
into the root from the soil
- DPD is increased by the negative tension, thus increased water uptake
Passive water absorption
87
- Does not concern the shoot
- Absorption of water occurs with the help of energy in the form of ATP, which is released due to metabolic activities of root cells such as respiration.
Active water absorption
88
Factors affecting rate of absorption of water:
1. Soil temperature
2. Concentration of soil solution
3. Aeration of soil
4. Availability of soil water
89
_____ soil temperature reduces water absorption because at _____ temperature water mobility is reduced, also the protoplasm is less permeable, and root growth is inhibited.
Low, low
90
______ concentrated soil solution means higher OP than OP of root
cells thus water will be drawn out of the plant.
More
91
_________ are plants that can tolerate high soil OP.
Halophytes
92
More O2, more H2O is absorbed because of its effect on ________.
respiration
93
Accumulation of CO2 in soil ________ protoplasm permeability retarding water absorption
decreases
94
Not all water in the soil is available to the plant, it is only those in the ________ of the root system that water is readily available.
immediate vicinity
95
water content of the soil after thoroughly wetting and then allowed to drain until capillary movement of water has essentially ceased, different types of soil may have different field capacity.
Field capacity (FC)
96
a percentage of soil water left when the leaves of the plant growing in the soil first exhibit symptoms of permanent wilting, dependent upon ability of plant to draw water so a type of soil may have different PWP depending on plant species.
Permanent wilting percentage (PWP)
97
sum of osmotic pressure of soil solution and soil moisture tension (gravitational, adsorptive and hydrostatic forces that hold water to the soil).
Total soil moisture stress (TSMS)
98
the movement of materials from leaves to other
tissues throughout the plant.
Translocation
99
The water and minerals absorbed by roots are conducted upwards to the leaves, flowers and other parts of the plant. It takes place through ________. The upward movement of sap that contains water and minerals is called ascent of _____.
xylem tubes, sap
100
cut end of a stump maybe observed
to exclude xylem sap
Root pressure theory
101
vital activities of plants especially those of living xylem tissues, fibers and parenchyma control ascent of water.
Vital force theory
102
Continuous column of water from the root to the stem to the shoot is maintained by the cohesive
forces of water and adhesive force that makes the column adhere to the surface of the xylem ducts.
Cohesion-tension theory
103
Phloem transport, A highly specialized process for redistributing:
- Photosynthesis products
- Other organic compounds (metabolites, hormones)
- Some mineral nutrients
104
any exporting region that produces photosynthesis above and beyond that of its own needs.
sources of phloem transport
105
any non-photosynthetic organ or an organ that does not produce enough photosynthate to meet its own needs.
Sink of phloem transport
106
Substances translocated in the phloem:
– Water
– Sugars
– Nitrogenous compounds – amino acids (aspartic and glutamic acids), amides (asparagine and glutamine), ureides (allantoic acid, allantoin)
– Hormones – auxins, gibberellins, cytokinins and abscisic acid
– Proteins – P proteins, etc.
– Inorganic solutes – K+, Mg2+ , HPO4 2- , Cl-
107
Sugars that are not in phloem
ketone, glucose, fructose, aldehyde, mannose
108
Sugars that are in phloem (polymers)
sucrose, raffinose, stachyose, verbascose
109
Phloem transport requires ________.
specialized living cells
110
Protective mechanisms in phloem
1.P proteins (Phloem proteins)
2. Callose
111
A protein found in large amounts in the sap-conducting sieve elements of phloem tissue in plants. It takes various forms in the mature sieve element, depending on plant species, ranging from a network of filaments to discrete crystalline bodies.
P-proteins
112
A plant polysaccharide. Its production is due to the glucan synthase-like gene (GLS) in various places within a plant. It is produced to act as a temporary cell wall in response to stimuli such
as stress or damage
Callose
113
Phloem transport is driven by _____ transport.
xylem
114
Phloem transport depends on water potential _______.
differences
114
The water potential differences are created by the selective transport of ________ into and out of the phloem
solutes (photosynthates)
114
Factors regulating loading of the sieve tube elements
* Existing solute potential and/or turgor pressure of the sieve elements
* External (apoplastic) sucrose concentration
* Availability and expression of sucrose transporters
* Nutrient supply
115
Source-sink pathways follow patterns
Proximity
Vascular connections
Development
115
upper leaves to upper portions, lower leaves to lower portions
Proximity
115
more direct vascular connection preferred
Vascular connections
116
importance of sinks changes with life cycle (reproductive)
Development
117
________ provide a means of rerouting photosynthate if the existing phloem is altered.
Anastomoses (singular anastomosis)
118
# Four main differences between xylem and phloem:
_____ is dead, where as _____ cells are alive.
Xylem, phloem
119
# Four main differences between xylem and phloem:
_____ carries mainly water and minerals, while organic compounds such as sugar and amino acids are transported to the _____.
Xylem, phloem
120
# Four main differences between xylem and phloem:
The flow of liquid in _____ is upward only, whereas the flow of liquid in _____ is bidirectional.
xylem, phloem
121
# Four main differences between xylem and phloem:
The contents in phloem can move ________ the plant simultaneously.
up and down
