Tag: transport of water in plants

Quizzes (0) Questions (77)

Questions Related to transport of water in plants

Multiple choice botany water absorption and ascent of sap in plants apoplast and symplastic pathway transport of water in plants water transport

In plants, water moves from 

  1. Less negative to more negative gradient

  2. More negative to less negative gradient

  3. Similar gradient

  4. Zero gradient
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
In plants, water is absorbed by roots from the soil and it has to get transported to all parts of the plant. Water moves only from the more negative gradient to a less negative or positive gradient. As when water concentration is high then the gradient is more negative and water always move from the higher concentration to lower concentration.
So, the correct answer is 'More negative to less negative gradient'.
Multiple choice botany water absorption and ascent of sap in plants apoplast and symplastic pathway transport of water in plants water transport

The rupture or fractionation do not usually occur in the water coloumn in vessels / tracheids during the ascent of sap because of

  1. lignified thick walls

  2. cohesion and adhesion

  3. weak gravitational pull

  4. transpiration pull
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The rupture or fractionation do not usually occur in the water column in vessels/ tracheids during the ascent of sap because of cohesion and adhesion. This is because continuity of water column is maintained by cohesion and adhesion. The conduction of water from root to aerial parts of plants is called ascent of sap. The water molecules remain attached to each other by cohesion force. The magnitude of this force is very high. This helps in the continuous water column in the xylem. The adhesive force is present between the water molecules and the walls of xylem. This also helps in continuous water column in the xylem.

Thus, the correct answer is option B.

Multiple choice botany water absorption and ascent of sap in plants apoplast and symplastic pathway transport of water in plants water transport

A column of water within xylem vessels of tall trees does not break under its weight because of

  1. Dissolved sugar in water

  2. Tensile strength of water

  3. Lignification of xylem vessels

  4. Positive root pressure
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The tensile strength of water is its ability to resist the effect of external stress and maintain it's flow. The transpiration all pull exerts great stress on the water column but due to its tensile strength, it doesn't break in between.

Dissolved sugar increases the solute potential while root pressure provides a push to water only up to a certain extent.
Lignin provides mechanical support to the xylem vessels.
So the correct answer is 'Tensile strength of water'.

Multiple choice botany water absorption and ascent of sap in plants apoplast and symplastic pathway transport of water in plants water transport

Relay pump theory of ascent of sap was proposed by

  1. Bose

  2. Godlewski

  3. Westermaler

  4. Von sachs
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Godlewski proposed relay pump theory to explain ascent of sap. According to him there was a rhythmic change in the osmotic pressure of the living cells of xylem parenchyma and medullary rays, which brought about a pumping action of water in an upward direction.

The tracheids and vessels acted as water reservoirs. Janse supported Godlewski and showed that if the lower portion of branch was killed, the leaves above were affected.


Multiple choice botany water absorption and ascent of sap in plants apoplast and symplastic pathway transport of water in plants water transport

Capillary force theory to explain ascent of sap was proposed by

  1. Boehm

  2. Sachs

  3. Jamin

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Capillarity Theory: It is given by Boehm (1809). According to this theory, water is translocated because water molecules adhere to the surfaces of small, or capillary, tubes. This adhesion causes water to somewhat creep upward along the sides of xylem elements. In glass tubes this upward movement is visible as the curved or crescent-shaped (concave) meniscus. However, it was shown that capillarity (or capillary rise) alone in tubes of similar diameter as that of a xylem element raises water less than 1 meter.

Hopkins (1999) explained that the relationship between the rise of water in a capillary tube and the size of the tube is inversely proportional. This means that the thinner is the tube, the higher will be the rise of water.

Multiple choice botany water absorption and ascent of sap in plants apoplast and symplastic pathway transport of water in plants water transport

Which of the following plant is ideal to demonstrate 'Ascent of sap'?

  1. Rose plant

  2. Balsam plant

  3. Coconut plant

  4. Cucumber plant
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The passage of absorbed water from root to the aerial parts of the plant is known as the ascent of sap. It occurs through xylem (lumen of tracheary elements or vessels and tracheids) with a rate of 10 to 75 centimetres per minute. This can be demonstrated by ringing experiments (conducted by Malpighi, 1672; Stephen Hales, 1727; and Hartig in 1837) or dipping the cut end of a fresh shoot (e.g., Balsam) in 2 percent eosin solution for about 30 minutes. Then, the veins of the leaves turn red. Sections through stem and leaves indicate that the xylem vessels/tracheids turn red.

Thus, the current answer is option B.

Multiple choice botany water absorption and ascent of sap in plants apoplast and symplastic pathway transport of water in plants water transport

Ringing experiment to explain ascent of sap path was first done by

  1. Hartig and Malpighi

  2. Dixon and J. C. Jolly

  3. Godlewski and J. C. Bose

  4. Stephen hales and Boehm
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Downward translocation of the organic solutes takes place through phloem. This can be proved by the ringing experiment. Ringing experiment was carried by Hartig, Malpighi and Stephen Hales.
They took a branch with leaves immersed in beaker which is filled with water. Now remove all the tissues which are present above the xylem [cortex, cambium and phloem]. Now placed this experiment in a suitable environment for 2 - 3 days. Then they observed that leaves did not wilt. This experiment makes it clear that water moves up only through vessels and tracheids of the xylem. 
Ringing [girdling] experiment has been done only in dicotyledons because their vascular bundles lies in a ring. While vascular bundles are scattered in monocotyledons, so that this experiment can not be possible.

Multiple choice botany water absorption and ascent of sap in plants apoplast and symplastic pathway transport of water in plants water transport

Sir J.C. Bose was supporter of _________ ascent of sap.

  1. Root pressure theory

  2. Physical force theory

  3. Vital force theory

  4. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Vital force theory:-
Berzelius proposed the origin of organic components by the vital force theory. According to today's organic components of synthesized only within living species.
Physical force theory:-
Godlewski explains the vertical movement of water to the plant. He said that changes in the water potential of the living cells like xylem parenchyma and medullary rays caused to raise water against gravity.
Root pressure theory:-
 It is proposed by Priestly. According to this theory, the water which is absorbed by the root hairs from soil collects in the cortical cells which becomes fully turgid. This pressure forces the water up to the xylem cells. 

Hence, the correct answer is option D.
Multiple choice botany water absorption and ascent of sap in plants apoplast and symplastic pathway transport of water in plants water transport

The following evidences rejected the atmospheric pressure theory. Which of them is correct?

  1. It can raise water to height of 33 feet only if complete vacuum is created.

  2. Free surface of water is required for proper operation of atmospheric pressure, which is readily available in plants.

  3. Pressure falls below that of atmospheric pressure because of transpiration.

  4. Water rises rapidly to compensate the water loss, because of atmospheric pressure.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Atmospheric pressure theory was advanced to explain ascent of sap in plants. The protagonists of this theory have assumed that plants are closed systems. When water escapes by transpiration from the surface of the leaves, it is believed that vacuum will be created within the plant body. As the root system is submerged in soil water, with the atmospheric action on the soil water, in order to fill up the vacuum created in the xylem vessels, water just enters passively; thus, the water is translocated upwards. But it was later on concluded that plants are not closed systems but they exhibit openness, for, the gases can diffuse into and out of the plant system with ease and facility. Added to this, atmospheric pressure can support the water to be lifted only to a height of 34 feet; but there are plants which are taller than this and still there is transport of water. Hence it can be concluded that atmospheric pressure could not be the force for ascent of sap.

Multiple choice botany water absorption and ascent of sap in plants apoplast and symplastic pathway transport of water in plants water transport

The imbibition theory for the ascent of sap was suggested by

  1. Sir J. C. Bose

  2. Strassburger

  3. Sachs

  4. Dixon and Jolly
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Imbibitions theory was proposed (1868) and supported by Sachs (1878). According to this theory the ascent of sap occurs due to imbibitonal activity of the cell walls of the xylem elements.

This theory is discarded as it has been experimentally found that water rises up through the lumen of the xylem and not through the walls.