Absorption by Roots Flashcards
1
Q
Define plant physiology. (2 points)
A
- Plant physiology is the branch of biology which deals with the life functions or metabolism of plants.
- It includes the functioning of cells, tissues, organs, organ systems and the organism as a whole.
2
Q
Give three names for the functions of the roots. Elaborate.
A
- Fixation
- Absorption
- Conduction
3
Q
Name the 5 purposes of water inside the plant body.
A
- Being a constituent of the protoplasm
- Photosynthesis
- Transpiration
- Transportation
- Mechanical Stiffness
4
Q
How is water used up in photosynthesis? (1 point only)
A
Water is used up in the green leaves as a raw material in the synthesis of glucose.
5
Q
How is water used up in transpiration?
1 point
A
A large quantity of water gets evaporated as water vapour during transpiration, for cooling in hot weather, for producing a suction force, etc.
6
Q
How is water used up in transportation?
A
Transportation of substances in water solution from the roots upward into the shoot (mineral salts) or from leaves to other parts (sugar, etc).
7
Q
How does water help in maintaining mechanical stiffness?
A
Water provides turgidity (fully distended condition), which is necessary for the stiffness of plant tissues.
8
Q
Name the forms in which minerals nutrients are absorbed from the soil by the roots.
A
- As salts
2. Simply as ions
9
Q
Name the salts absorbed by the roots from the soil.
A
Nitrates, Phosphates, Sulphates, etc.
10
Q
Name the ions absorbed by the roots from the soil.
A
Potassium, calcium, magnesium - (chlorophyll is made up of magnesium), chlorine, etc.
11
Q
Name the functions of these mineral nutrients in the plant.
A
- They are required as constituents of cell and cell organelles.
- They are required in the synthesis of a variety of compounds or enzymes within the cell (chlorophyll is made up of magnesium).
12
Q
Name the three characteristics on which the ability of plants to draw water from roots depends.
A
- A huge surface area provided by rootless and root hairs.
- Root hairs containing the solution (cell sap) at a concentration higher than that of the surrounding soil water.
- Root hairs having thin walls.
13
Q
Explain the role of surface area of roots in absorption of water.
A
The surface area is increased by the presence of a thick bunch of rootlets (branch roots) and hundreds of root hairs.
Example - The small garden plant balsam has a thick bunch of rootlets and hundreds of root hairs.
14
Q
Name the botanist who worked out that that the roots of any plant provide a huge surface area to facilitate the absorption of water.
A
Botanist - H.J. Dittmer (1937) Plant used - a four month old rye plant Aggregate root length - 600 km No. of root hairs - more than 14 billion Estimated total length of root hairs - exceeding 10,000 km
15
Q
What is sap?
A
Water along with mineral salts absorbed by the roots
16
Q
Root hairs are the extensions of?
A
outer (epidermal) cells of the root.
17
Q
Root hairs contain large _ filled with a solution called _?
A
vacuoles, cell sap
18
Q
Why does the cell sap have a higher concentration than that of surrounding water?
A
Due to dissolved salts.
19
Q
Which characteristic of the root hair is important to draw water from the outside?
A
Having cell sap which has a higher concentration than that of the surrounding soil water.
20
Q
This ‘higher concentration’ characteristic promotes which process?
A
Osmosis
21
Q
Name the two outer layers of root hair.
A
Cell wall and cell membrane.
22
Q
Name the characteristics of cell wall & consequently, what it allows.
A
The cell wall is thin and freely permeable. It allows the movement of water molecules and dissolved substances freely in and out of the cell.
23
Q
Name the characteristics of cell membrane & consequently, what it allows.
A
The cell membrane is very thin, non-cutinised and semi-permeable, which means it allows water and molecules to pass through, but not the larger molecules of the dissolved salts.
24
Q
In which characteristic does the secret of absorption of water from soil by roots lie?
A
In the cell membrane’s semi-permeability - it allows water molecules to pass through, but not the larger molecules of the dissolved salts.
25
Name the fine main phenomena, the result of which is the entire mechanism of absorption & conduction.
1. Imbibition
2. Diffusion
3. Osmosis
4. Active Transport
5. Turgidity and Flaccidity
26
Define imbibition.
Imbibition is a phenomenon in which the living or dead plant cells absorb water by surface attraction.
27
Which substances have a strong affinity for water? Name the state of having this affinity.
Substances which are made up of cellulose (in cell wall) or proteins (starch) are hydrophilic (strong affinity for water).
28
What do hydrophilic substances do when in contact with moisture?
The imbibe water or moisture and swell up, e.g., dry seeds, wooden doors. swell up on contact with water or exposure to moist air.
29
Name two consequences of imbibitional pressure.
1. Seed coat ruptures in case of germinating seeds.
| 2. It is an important force in the ascent of sap.
30
Define diffusion.
Diffusion is the free movement of molecules of a substance (solute or solvent, gas or liquid) from the region of their higher concentration to their lower concentration when the two are in direct contact.
31
Give an example of diffusion in plants.
Exchange of respiratory gases, transpiration
32
Give an example of diffusion in animals.
Exchange of respiratory gases in the alveoli
33
Name the requirements in the experiment demonstrating diffusion.
1. Sugar cube/ crystal of potassium permanganate/ small tablet of a soluble dye
2. Beaker
3. Water
34
Give the steps of the experiment which demonstrates diffusion.
1. Place a sugar cube or a small tablet of a soluble dry or a crystal of potassium permanganate in a beaker containing water, in one corner.
35
Describe what happens in the experiment demonstrating diffusion.
1. The molecules of dye are more concentrated in and near the tablet of dye.
2. Molecules move farther away to regions where they are less concentrated.
3. This movement continues until molecules are uniformly distributed.
36
Name the step used to hasten the process of diffusion in the experiment.
1. Stirring with a spoon or a glass rod hastens the process and you get a homogeneous solution much faster.
37
Define osmosis.
Osmosis is the movement of water molecules from their region of higher concentration (dilute solution or with a lower solute concentration) to their region of lower concentration (concentrated solution or with a higher solute concentration) through a semi-permeable membrane.
38
Define endosmosis
It is the inward diffusion of water through a semi-permeable membrane when the surrounding solution is less concentrated. This tends to swell up the cell.
39
What is the function of endosmosis?
It tends to swell up the cell.
40
Define exosmosis.
It is the outward diffusion of water through a semi-permeable membrane when the surrounding solution is more concentrated. Tends to cause shrinkage of cell.
41
What is the result of exosmosis?
Shrinkage of cell.
42
What are the requirements for the experiment demonstrating osmosis?
1. Concentrated sugar solution
2. Thistle funnel
3. Cellophane paper
4. Beaker containing water
43
State the steps in the experiment demonstrating osmosis with a thistle funnel.
1. Take some concentrated sugar solution in a thistle funnel.
2. Cover the mouth of the thistle funnel with a cellophane paper.
3. Invert the thistle funnel in a beaker containing water and suspend it.
4. Mark the level of the sugar solution on the stem of the thistle funnel.
44
What is the difference between the control set-up and the experimental setup in the experiment demonstrating osmosis using a thistle funnel?
The thistle funnel will have plain water instead of a concentrated sugar solution, as a control.
45
State the observations in the experiment demonstrating osmosis using a thistle funnel.
1. After a few hours, the level of the sugar solution in the thistle funnel in the experimental setup will rise.
2. Level of water in control will remain unchanged.
3. In beaker in experimental setup will drop slightly while the beaker in control will remain unchanged.
4. If water in beaker in experimental setup is tasted, it is not found sweet.
46
State the main takeaways from the thistle funnel experiment.
1. In the experimental setup, some water of the beaker has passed through the cellophane paper to enter the thistle funnel containing sugar solution.
2. Sugar from the thistle funnel has not passed the beaker.
3. Here, the cellophane sheet acts as a selectively permeable membrane in that it allows onto water molecules from the beaker to pass into the thistle funnel and not the larger sugar molecules to paas into the beaker from the thistle funnel.
47
What would happen if in the experiment demonstrating osmosis, a more concentrated sugar solution would be taken in the thistle funnel and a very dilute sugar solution in the beaker?
The result would still be the same, the level of solution in the thistle funnel would rise.
Why - Some water from the dilute solution would move into the concentrated solution through the cellophane paper.
48
What would happen if we were to use a rubber sheet in the experiment demonstrating osmosis?
No change in the level of sugar solution would occur as the rubber sheet is impermeable and does not allow the water molecules from the beaker to cross over to the other side.
49
What would happen if we were to use a muslin cloth in the experiment demonstrating osmosis?
The meshes or pores of the muslim cloth are so large that they would not hold back even the sugar molecule, and the entire sugar solution would flow down to common level due to gravity.
Muslim cloth is therefore freely permeable for sugar solution.
50
Give alternative requirements to perform the same osmosis experiment.
1. Visking bag (semi-permeable membrane)
| 2. Long glass capillary tube
51
What are the steps taken in the experiment with the visking bag?
1. Place sugar solution in a knotted visking bag and insert a long glass capillary tube till some of the sugar solution rises into the capillary tube.
2. Tie the mouth of the bag firmly round the capillary tube and support it on a clamp stand.
3. Immerse the visking bag in a beaker with water.
4. After about an hour, the level of sugar solution in the capillary tube rises.
5. This rise is due to water molecules diffusing through the visking bag.
52
What are the key points in the above osmosis experiments?
1. There are two liquids of different concentrations.
(i) Two regions of different conc. of water molecules
(ii) Two regions of diff. conc. of sugar molecules.
2. The two liquids are separated by the cellophane sheet which acts as a semi-permeable membrane - allows the passage of molecules selectively.
53
How long can osmosis continue?
Theoretically, till the concentration of water molecules is equal on both sides of the membrane.
54
What prevents further osmosis despite unequal concentration?
When water molecules from one medium try to force through the membrane, but the weight or pressure of the other medium holds them downwards.
55
Why does osmosis not continue in the thistle funnel experiment?
Because with the influx of water from the beaker, the height and weight of the column of sugar solution increase. In this state of unequal equilibrium, the water molecules from the beaker tend to force upwards through the membrane, but the weight of pressure from above holds them downwards.
56
What would happen if an airtight piston would be used in the thistle funnel experiment?
The level of solution would not rise at all, showing thereby that there was no entry of water.
57
Define osmotic pressure.
Osmotic pressure is the minimum pressure that must be exerted to prevent the passage of the pure solvent into the solution when the two are separated by a semi-permeable membrane.
58
Define osmotic pressure simply (1 line)
Osmotic pressure is a measure of the solution's tendency to take in water by osmosis.
59
What is osmotic pressure equal to?
To the weight or pressure required to nullify osmosis.
60
Define tonicity.
Relative concentration of the solutions that determine the direction and extent of diffusion is called tonicity.
61
Name the three types of solutions based on tonicity.
1. Isotonic
2. Hypotonic
3. Hypertonic
62
Define isotonic solution.
In an isotonic solution, the relative concentration of water molecules and the solute on either side of the cell membrane is the same. In such a solution, there is no net movement of water molecules across the cell membrane. No osmosis occurs.
63
Define hypotonic solution
In a hypotonic solution, the solution outside the cell has a lower solute concentration than the fluids inside the cell. As a result, water molecules from outside will move into the cell. (endosmosis)
64
Define hypertonic solution.
In a hypertonic solution, the solution outside the cell has a higher solute concentration than the fluids inside the cell. Consequently, the water molecules from the interior of the cell will move out. (exosmosis)
65
What happens to a cell when placed in an isotonic solution?
Cell size and shape remain unchanged
66
What happens to a cell when placed in a hypotonic solution?
Cell slightly enlarges or even bursts.
67
What happens to a cell when placed in a hypertonic solution?
Cell shrinks in size and loses its shape.
68
What is a turgid cell?
A cell is called turgid when it is fully distended, i.e. when it cannot withstand any further inflow of water molecules.
69
In the case of plant cells, which extra feature determines the behaviour of the cell when subjected to varying external fluid environments?
This feature is the rigidity of the cell wall which resists bulging and protects the delicate cellular parts inside.
70
What are the phenomena related to the rigidity of the cell wall?
Turgidity, plasmolysis, and flaccidity
71
Conversely, what does the rigidity of the cell wall determine?
It determines the behavior of the cell when subjected to varying external fluid environments.
72
What does a semi-permeable membrane allow but prevents?
It allows a solvent to pass through it freely but prevents the passage of the solute.
73
Define active transport.
Active transport is the passage of a substance (salt or ion) from its lower concentration to its higher concentration using energy from the cell through a living cell membrane.
74
How are the directions of active transport and diffusion different?
Active transport is in a direction opposite to that of diffusion.
75
Which nutrients cannot pass through the cell membrane of root cells easily?
Ions of nitrates, sulphates, potassium, zinc, manganese, etc.
76
What do the ions of nitrates, sulphates, potassium, zinc, manganese have in common?
They cannot pass through the cell membrane of root cells easily.
77
Why can certain nutrients not pass through the cell membrane of the root cells easily?
This is because their concentration is higher inside the root cells and these ions will need to be forcibly carried inward from a region of their lower concentration to higher concentration inside, and this requires energy in the form of ATP.
78
Why is the concentration of certain nutrients higher inside the root cell?
To develop osmotic pressure for absorbing water from the surrounding soil water.
79
Explain how the concentration gradient of certain nutrients in osmosis is different from that in diffusion.
The concentration of these nutrients is higher inside the root cells, and it is so maintained in order to develop osmotic pressure for absorbing water. In diffusion, however, ions move from a region of their higher concentration to their lower concentration.
80
What does the forceful transport of nutrients into the cell require?
Energy supplied by the cell in the form of a shit ton of ATP.
81
Define passive transport.
Passive refers to requiring no input of energy. there is a free movement of molecules from their region of higher concentration to their region of lower concentration.
82
What are the root hairs particularly surrounded by?
Soil water
83
Which cells are subjected to osmosis?
Every living plant cell directly or directly is in contact with fluids. All such cells (root hairs) are subjected to osmosis and the water continues to enter.
84
On what condition will cells be subjected to osmosis?
As long as the cell sap is more concentrated than the surrounding fluids, osmosis will occur.
85
When is a cell called turgid?
When a cell reaches a state when it cannot accommodate any water, i.e. it is fully distended, it is called turgid.
86
What is turgidity?
The state in which the cell wall is rigid and stretched by an increase in the volume of vacuoles due to the absorption of water. The cell is then said to be turgid.
87
Define turgor pressure.
During turgidity, the pressure exerted by the cell contents on the cell wall is called turgor pressure.
88
Define wall pressure.
During turgidity, the pressure exerted by the cell wall on the cell content is called wall pressure.
89
How are turgor and wall pressure related?
They occur simultaneously. When a cell is turgid, its wall is stretched under the pressure from inside, and in its turn, it presses the cell contents towards the centre of the cell.
90
Why do fruits and vegetables sometimes burst?
If, at any time, the cell wall is unable to bear the turgor pressure, it ruptures and the cell contents burst out.
91
What state is a cell in when turgid?
It is in a somewhat balanced state.
92
Explain how the cell is in a balanced state when turgid.
No more water is entering or leaving the cell. Its turgor pressure counter-balances the wall pressure and therefore, there is no further absorption of water even though the concentration of solutes inside the cell may be greater than outside the cell.
93
State a difference between diffusion, osmosis, and active transport with reference to distance.
1. Liquids and gases can diffuse over considerable distances.
2. Water only transported over a short distance (osmosis)
3. Cell energy is needed for transpiration.
94
State a difference between diffusion, osmosis, and active transport with reference to substance.
1. Movement of molecules of solute or solvent.
2. Movement of molecules of only water as a solvent.
3. Movement of ions only, other than water.
95
State a difference between diffusion, osmosis, and active transport with reference to speed.
1. Rapid in gases, but slow in solutions.
2. Slow process
3. Rapid process
96
State a difference between diffusion, osmosis, and active transport with reference to concentration gradient.
1. Transport from high to low conc. along a gradient.
2. Transport of water from a solution of low concentration to that of high conc.
3. Movement of molecules against a concentration gradient.
97
State a difference between diffusion, osmosis, and active transport with reference to membrane.
1. With or without a non-living permeable membrane.
2. Living or non-living semi-permeable membrane.
3. A living selective membrane is essential.
98
Define plasmolysis.
It is the contraction of the cytoplasm from the cell wall caused due to withdrawal of water when placed in a strong (hypertonic) solution.
99
Define flaccidity.
It is the condition in which the cell content is shrunken and the cell is no more "tight". The cell is then said to be flaccid.
100
What is the state of the plant cell when placed in fresh water?
It is fully distended - its plasma membrane remains in close contact with the cell wall and presses against it.
101
What comparison has been drawn to show how plasma membrane remains in close contact with the cell wall?
Like a rubber bladder of a football pushing against the leather casing.
102
What happens if a fully distended cell is placed in a 5% salt solution?
It will lose its distended appearance, the cytoplasm will shrink and the plasma membrane will withdraw from the cell wall.
103
How are flaccidity and turgidity related?
Flaccidity is the reverse of turgidity.
104
What happens when a plasmolyzed cell is returned to water before it's dead?
Its protoplasm again swells up pressing tight against the cell wall.
105
What is deplasmolysis?
The recovery or the reversal of plasmolysis is called deplasmolysis. Plasmolysis is the result of outflow of water from the cell and deplasmolysis is the result of its re-entry.
106
Name the uses of turgidity to plants.
1. It provides rigidity to soft tissues such as the leaves.
2. Turgor pressure helps to push through the hard ground.
3. Turgor in root cells build up root pressure.
4. Turgor in the opening and closing of stomata.
5. Turgor movement
107
What happens when there is not enough water in a leaf?
It wilts, i.e. its petiole and lamina become loose and the leaf droops down.
108
When is wilting of leaves usually noticed?
When a plant is exposed to the hot afternoon sun when the amount of water lost during transpiration is more than the water absorbed through the roots.
109
What happens in the evening to wilting leaves?
In the evening, transpiration is reduced, the quantity of water absorbed exceeds the loss of water through transpiration, the turgidity of leaf cells is restored and the leaves again stand out.
110
Name two applications of plasmolysis in practice.
1. Salting of meat or addition of salt to pickles is a method of killing bacteria by plasmolysis - water is drawn out of the bacterial cells.
2. Weeds can be killed in a playground by sprinkling excessive salts around their base.
111
What is the one disadvantage of using plasmolysis to kill bacteria?
Excessive application of fertilizers in the agricultural fields may similarly damage the roots and diminish the yield.
112
In which cases does turgor pressure help to push thru the hard ground?
In mushrooms and seedlings.
113
Why do the roots of certain trees crack the walls or concrete floors of the adjoining building?
Due to turgor pressure.
114
Define root pressure.
Root pressure is the pressure developed in the roots due to continuous inward movement of water through cell-to-cell osmosis which helps in the ascent of sap upward through the stem.
115
Upward flow of water from a cut stem through the connecting rubber tube to raising the mercury level in the manometer is a result of?
Root pressure
116
What is bleeding?
Loss of water (cell sap) through a cut stem is called bleeding.
117
What does the opening and closing of stomata depend upon?
Depends upon the turgidity of the guard cells.
118
Define the external structure of the guard cell.
Each guard cell has a thicker wall on the side facing the stoma and a thin wall on the opposite side.
119
What do guard cells contain?
chloroplasts
120
Why does the osmotic pressure increase in guard cells?
As a result of the synthesis of glucose during photosynthesis and some other chemical changes.
121
What happens as a result of increased osmotic pressure in guard cells?
They absorb more water from the neighboring cells, thus becoming turgid.
122
What happens on account of turgor which is a result of increased osmotic pressure?
The guard cells become more arched outwards and the aperture between the widens, thereby opening the stomata.
123
What happens to the stomata at night?
At night, or when there is shortage of water in the leaf, the guard cells turn flaccid and their inner rigid walls become straight, thus closing the stomatal aperture.
124
Give an example of turgor movement.
The rapid drooping of the leaves of the sensitive plant (Mimosa pudica) is an outstanding example of the turgor movement.
125
Name a sensitive plant
Mimosa pudica
126
What happens if the leave of Mimosa pudica is touched, externally?
The leaflets fold up, and within 2-3 seconds, the entire leaf droops. When it is touched strongly, the wave of folding and drooping spreads from the stimulated leaf to the neighbouring leaves.
127
What happens if the leave of Mimosa pudica is touched, internally?
In this plant, the stimulus of touch leads to loss of turgor at the base of the petioles called the pulvinus, and the leaf droops.
128
What is the base of the petioles called?
Pulvinus
129
Give 3 examples of turgor movements, aside from Mimosa pudica.
1. Turgor movements found in insectivorous plants whose leaves close up to entrap a living prey.
2. The bending movement of certain flowers towards the sun.
3. The sleep movements of the leaves of certain plants at night.
130
Give another definition of turgor, with reference to the type of osmosis.
Turgor is the pressure set up inside the plant cells due to hydrostatic pressure on the cell walls on account of incoming water as a result of endosmosis.
131
How do imbibition and turgor movement generate much force together?
Imbibition is the passive absorption of water by substances such as cellulose (in cell wall) and starch. Turgor is the pressure set up inside the plant cells due to hydrostatic pressure on the cell walls on account of incoming water as a result of endosmosis. Both of these result in the swelling up of seeds and grains when they're being soaked in water.
132
Why do seeds and grains swell up when soaked in water? Why do seed coats bursts when kept in water?
This is due to imbibition as well as turgor force acting on them together. The force generated by the water thus absorbed is strong enough to make the seed coats burst.
133
Soaked seeds in a fully filled closed container burst it open with great pressure. Why?
This is because these seeds swell up due to imbibition and turgor. The force generated by the water thus absorbed is strong enough to make the seed coats burst. Seeds absorb water and swell up and exert pressure on the walls and opening of the container which burst it open.
134
Why do basement godowns, fully stocked with bags containing foodgrains, have cracked walls after the rainwater has flooded in?
This is because the food grains swell up due to imbibition and turgor. The force generated by the water thus absorbed is strong enough to make the foodgrains burst, which then exert pressure on the walls of the basement godown.
135
What happens when you cut off the stem of the plant & due to which force?
Water pushes out from the root stump, due to root pressure.
136
What is root pressure built up due to?
Root pressure is built up due to cell-to-cell osmosis in the root tissue. As one turgid cell presses the next cell, the force of the flow of water increases inward.
137
How doe root pressure raise water through the stem into the leaves?
When the water absorbed by the roots reaches the xylem vessels (centrally placed vertical channels) after cell-to-cell osmosis, it enters the pores of the thick walls of the xylem vessels with great force.
138
What is guttation?
In certain plants, like tomato, grass, banana, or ferns, the root pressure is high enough to force the water all the way through the stem and comes out through the end of leaf veins. This water appears as tiny droplets along the margins or the tips of the leaves, especially in the early mornings. This excessive loss of water is called guttation.
139
In which plants does guttation occur?
Tomato, grass, banana, ferns.
140
How does water appear in guttation?
The water appears as tiny droplets along the margins or the tips of the leaves of the plant.
141
When does guttation especially occur?
In the early mornings.
142
Why does guttation occur in the night or early mornings?
Stomata tend to be closed at night (when it is dark), so there is very little or no transpiration occurring at night, hence root pressure is 'fully' expressed at the leaf margins & guttation is possible. When there is high atmospheric humidity and less or no transpiration occurs as most plants have their stomata closed, guttation occurs.
143
Which two factors help to push water upwards thru xylem vessels?
Root pressure & turgidity acquired by the cells in the process of cell-to-cell osmosis.
144
What is the pathway of the water absorbed from roots?
From the cell bearing the root hair, water continues to pass into the adjoining cells one after another to finally enter the xylem vessels.
145
What are minerals absorbed as from soil water?
Ions rather than salts
146
How are mineral elements absorbed by the root hair?
Through active transport
147
What can this dilute solution of water and mineral salts absorbed be used for?
For food manufacture by the leaves, only if it can travel up to the highest points of the plant.
148
In the experiment demonstrating that roots absorb water which is being transpired by the leaves, what are the requirements?
1. 2 test tubes filled with equal levels of water
2. Oil
3. Young leafy plant (Balsam)
149
In the experiment demonstrating that roots absorb water which is being transpired by the leaves, what are the steps taken?
1. Take a TT A filled with water. Mark the level of water in and put a few drops of oil in it to prevent any loss of water by evaporation. (for control setup)
2. Take a TT B with same level of water. Pull out a young leafy plant from the soil with its roots intact and insert the roots of the plant in TT. Put a few drops of oil.
150
In the experiment demonstrating that roots absorb water which is being transpired by the leaves, what is the observation after a day?
The level of water in TT B falls but not in TT A.
151
In the experiment demonstrating that roots absorb water which is being transpired by the leaves, what is the inference?
Water lost in TT B was absorbed by the roots.
152
In the experiment demonstrating that roots absorb water which is being transpired by the leaves, why is oil put in the test tube?
To prevent loss of water by evaporation, since aim of experiment is to see if roots absorb water which leaves lose through transpiration.
153
In the experiment demonstrating that water is conducted upwards through xylem, what are the requirements?
1. A medium-sized young balsam plant
2. Beaker containing stain eosin solution (pink) in water
3. Microscope
4. Tap water
154
In the experiment demonstrating that water is conducted upwards through xylem, what are the steps?
1. Uproot a medium-sized young balsam plant, wash, and place in a beaker containing a stain eosin solution (pink) in water.
2. Keep the set-up aside for 3-4 hours.
3. The plant is taken out of the solution and washed in tap water.
4. A transverse section of the roots, stem, and leaves is made and examined under a microscope.
155
In the experiment demonstrating that water is conducted upwards through xylem, what are the observations?
The xylem vessels will appear distinct from the rest because these will be stained red by the dye.
156
In the experiment demonstrating that water is conducted upwards through xylem, what are the precautions?
1. The roots should be completely submerged in the solution.
2. The set-up should be kept aside for at least 3-4 hours.
3. Plant should be washed thoroughly with tap water.
157
What are the components of the transport system in plants?
Vascular bundles in the stem, root, leaf stalks (petiole), and leaf veins are all continuous and form an unbroken system of tubes, making the plant's transport system.
158
What does xylem conduct and in which direction?
Water and salt travel upwards mainly in the xylem
159
What does phloem conduct and in which direction?
Food substances travel up and down in the phloem.
160
In the delicate experiment demonstrating that water is conducted upwards through the xylem, what are the requirements?
1. 2 leafy shoots
| 2. 2 beakers filled with water
161
In the delicate experiment demonstrating that water is conducted upwards through the xylem, what are the steps?
1. Take 2 leafy shoots-those of balsam plant, which have been cut under water.
2. Keep their lower ends dipping in water.
3. Remove about 3cm long, outer ring (phloem) of the stem in beaker A, keeping the central part intact.
4. In the other beaker, remove an equal length of central part after incising the stem for full thickness and keeping the peripheral part intact.
5. The shoots are fixed to stands and allowed to stand for 2 days with lower ends in water.
162
In the delicate experiment demonstrating that water is conducted upwards through the xylem, what are the observations?
The leaves in the first twig remain turgid and stand out almost normally, but those in the second twig get wilted and droop down.
163
In the delicate experiment demonstrating that water is conducted upwards through the xylem, what are the precautions?
1. Cut the leafy shoot under water to prevent entrance of air bubbles.
2. The lower ends of shoots should be dipped in water of the beaker.
3. Incise the stem for full thickness before removing an equal length of xylem carefully.
4. Keep the central part intact while removing the phloem.
5. Make sure the lower ends of the shoots in the two days are immersed in water.
164
In the delicate experiment demonstrating that water is conducted upwards through the xylem, what is girdling?
Removing the phloem while keeping the central part (xylem) intact.
165
In which experiment is girdling used?
In the delicate experiment demonstrating that water is conducted upwards through the xylem
166
In the experiment to show the food from leaves is conducted downwards thru phloem in the stem, what are the requirements?
1. Healhty potted plant or a thin twig of guava
167
In the experiment to show the food from leaves is conducted downwards thru phloem in the stem, what are the steps?
1. Cut a ring around the stem of a healthy potted plant or a thin twig of guava, deep enough to penetrate the phloem and cambium but not the xylem.
168
In the experiment to show the food from leaves is conducted downwards thru phloem in the stem, what are the observations?
1. The sap starts oozing out from the farther-cut margin of the stem, showing thereby that sap in the peripheral part flows in a downward direction.
2. After some weeks, it will be observed that the part of the stem above the ring has grown in diameter, and the stem below the girdle has stopped growing and may even die when the stored organic contents of the lower part are exhausted.
169
In the experiment to show the food from leaves is conducted downwards thru phloem in the stem, why are the leaves fresh and healthy?
Leaves continue to get a constant supply of water through a deeper located, intact xylem.
170
In the experiment to show the food from leaves is conducted downwards thru phloem in the stem, what are the precautions?
1. Cut deep enough to penetrate the phloem and cambium but not the xylem.
171
In the experiment to show the food from leaves is conducted downwards thru phloem in the stem, why has the area above the ring grown in diameter?
This is because phloem conducts the food produced by the leaves downwards in the stem. The removal of a ring of phloem in the middle of the stem prevents the conduction of the prepared food further and results in an accumulation of food right above the ring.
172
Which part of the stem, the xylem or the phloem is located deeper internally?
The xylem is deeply located, as it is the central part.
173
In the experiment demonstrating that water is conducted upwards through the xylem, why was it necessary to take coloured eosin solution in the water in the beaker?
The aim of the experiment was to prove that water is conducted upwards through the xylem, and the usage of coloured dye in water stains the xylem and makes it appear distinct from the rest, thus proving that it is the xylem that carries the water that had the dissolved dye.
174
Name the forces contributing to the ascent of sap.
1. Root pressure
2. Capillarity
3. Transpirational Pull
4. Adhesion
175
How does root pressure contribute to the ascent of sap?
Root pressure builds up sufficient force to push the sap in the xylem vessels up to a certain height and may be enough for herbaceous plants.
176
How does capillarity contribute to the ascent of sap?
Capillarity (narrow diameter) of xylem vessels causes the water from a lower level to rise to fill up the vacuum created by the loss of water due to transpiration from the leaves. Narrower the diameter, greater will be the height of water rising in it.
177
Define capillary force.
Capillary force is a resultant force exerted by the rising height of water in a tube, due to the narrow diameter of the tube. (Narrower the diameter, greater will be the height of water rising in it)
178
How does transpirational pull contribute to the ascent of sap?
As water is lost from the leaf surface by transpiration, more water molecules are pulled up due to the tendency of water molecules to remain joined (cohesion), and thus to produce a continuous column of water through the stem.
179
How does transpirational pull contribute to the ascent of sap?
It causes the water to stick to the surface of cells thus drawing more water molecules from below when the leaf cells lose water during transpiration.
180
Why is adhesion important in tall trees?
This pulling force (or suction force) provided by the leaves is especially important in tall trees because they do not have enough root pressure.
181
What is cohesion?
Cohesion is the molecular attraction by which the particles of a body are united throughout the mass.
182
Explain cohesion in a coconut.
All the water inside the coconuts comes from the ground. As one molecule of water evaporates from the leaves during transpiration, another molecule rises up to fill its place and this goes on in succession throughout the tall stem right from the roots.
183
The downward movement of sap happens because?
The food manufactured in leaves is dissolved in water and it flows down mainly on account of the force of gravity.
184
Give an example of a tree in which adhesion occurs.
Pine
185
Wilting occurs due to?
Due to loss of turgidity
186
What is water potential?
Capacity to move out to higher concentrated solution
187
Which substance has the highest water potential?
Pure water
188
The space between the cell wall and plasma membrane in a plasmolysed cell is filled with?
Water
189
Name the pressure which is responsible for the movement of water molecules across the cortical cells of the root
Root pressure
190
Name the term for the inward movement of solvent molecules through the plasma membrane of a cell
Endosmosis
