Tag: botany

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

Ringing experiments are performed to demonstrate

  1. Ascent of sap through both phloem and xylem.

  2. The ascent of sap through phloem and xylem parenchyma.

  3. The ascent sap through cortical cells.

  4. Ascent of sap through xylem.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In ringing experiment the bark of a tree is removed at a height above the soil surface as a ring. This leads to accumulation of sugars just above the ring of bark removal because sugars are transported through phloem. The ascent of sap which occurs through xylem continues normally because xylem is not part of the bark and bark consists of secondary phloem along with several other tissues.The experiment clearly demonstrates the function of xylem.

Thus, 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

Mostly minerals are absorbed from the soil by the plant 

  1. By a process dependent of water absorption

  2. Only when soil solution is hypotonic to cell sap

  3. Only when soil solution is hypertonic to cell sap

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

In soil, the minerals can be present dissolved in soil solution or adsorbed on charged clay particles. Plants obtain minerals both from the soil solution (through absorption) as well as directly from clay particles (through ion exchange mechanisms). 

Mineral absorption can be active or passive. The passive mineral absorption can occur both in the direction as well as against concentration gradient. Mass flow is one mechanism through which minerals are absorbed passively against their concentration gradient. In mass flow, mineral ions are swept into root and passed into the plant parts along the current of water, caused by transpiration pull. Mineral absorption depends on water absorption because the solvent of soil solution is water. Mineral absorption can occur along with the water stream. Minerals can also be absorbed actively involving the expenditure of metabolic energy irrespective of the tonicity of the soil solution.
So, the correct answer is option A.

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

The chief role of transpiration in plants is to

  1. Remove surplus water

  2. Cooling of the plant

  3. Increase ascent of sap

  4. Uptake rise of minerals
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to the most widely accepted theory, ascent of sap occurs through 'Cohesion Tension' or 'Cohesion Transpiration pull'. The cohesion and adhesion forces give rise to a continuous water column in xylem elements, which is lifted by the transpiration pull. Thus, ascent of sap is purely physical process and does not involves energy input.

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

The main path for movement of water against the force of gravity i.e., ascent of sap in herbaceous dicots is

  1. Tracheids

  2. Vessels

  3. Sieve tubes

  4. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Xylem tissue is a complex permanent tissue specialized to transport water in plant body. Xylem tracheids are found in a number of plant groups like angiosperms, gymnosperms and pteridophytes. Bryophytes do not possess vascular tissues. Hence, bryophytes do not attain height. Xylem tracheids are present in pteridophytes and gymnosperms. These plant groups lack vessels. Vessels are characteristics of angiosperms only. In angiosperms, xylem vessels form the main channel 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

Vital theories of ascent of sap were discarded due to reasons that

  1. Living cells are involved.

  2. Metabolic activity provides energy requirements.

  3. Water continues rising even after killing of xylem parenchyma.

  4. Atmospheric pressure is involved in ascent of sap.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Vital force theories were propagated to explain the ascent of sap. These theories believed that living cells are involved in the ascent of sap e.g., relay pump theory by Godlewski, 1883 and pulsation theory by Bose, 1923. Bose believed that the inner most cortical cells pump water into the interior, that contains xylem channels. The vital force theories have been discarded because as proved by Boucherie in 1840 and Strasburger in 1891 that water rises up the stem, even when all the living cells are killed by poison or heat.

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

When an oak tree is kept in a poisonous solution, water rises to the top of the tree, although the tree is ready to take another supply of poisonous solution followed by uptake of even pure water. This shows that

  1. Living cells are not involved in ascent of sap.

  2. Living cells play a major role is ascent of sap.

  3. Both xylem and phloem play a major role in ascent of sap.

  4. Living cells play 60% role and vessels of xylem play 40% roles in ascent of sap.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ascent of sap occurs through non living xylem tracheids and vessels. The force responsible for pull of water to great heights is the transpiration pull. The properties of adhesion, cohesion and capillarity helps in ascent of sap through non living tracheids and vessels.

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 statement is incorrect?

  1. Plants absorb excess quality of water

  2. Plants take small quantity of mineral salts through soil water

  3. Water and inorganic salts may also simultaneously by root hair

  4. Plant absorb only one thing at a time, i.e., either water or inorganic salts
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Plants absorb water through the entire surface - roots, stems and leaves. However, mainly water is absorbed by roots. They also absorb minerals like nitrogen, phosphorus, etc., from the soil through their roots. The root hairs which are in close contact with the thin film of water surrounding the soil particles absorb the mineral salts such as nitrates, chlorides, sulphates, phosphates, etc., dissolved in this water. However, the concentration of minerals in the soil is very low.

So, 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

Water will be absorbed by root hairs when

  1. Concentration of salts in the soil is high.

  2. Concentration of solutes in the cell sap is high.

  3. The plant is rapidly respiring.

  4. They are separated from the soil by a semipermeable membrane.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Water moves from a region of its own high concentration to a region of its own low concentration. If the cell sap is highly concentrated as compared to soil solution- it means water molecules are present in high concentration in the soil solution and in low concentration in the cell sap. In such a situation water molecules will move along their concentration gradient and readily move inside the root hairs.

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

Pulsation theory to explain ascent of sap in Desmodium was proposed by

  1. Dixon and Jolly

  2. Curtis

  3. J. C. Bose

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

"Pulsation" or "Vital force" theory was a proposed mechanism for the ascent of sap through the xylem tissue of plants according to which, the conduction of water up the xylem vessel is a result of vital action of the living cells in the xylem tissue.
Jagadish Chandra Bose suggested this mechanism for the ascent of sap in 1927. He found electrical pulsations or oscillations in electric potentials, and came to believe these were coupled with rhythmic movements in the telegraph plant Desmodium. However, this theory has now been rejected by majority of plant physiologists.

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

Passage of ascent of sap is shown by

  1. Osmometer

  2. Porometer

  3. Manometer

  4. Blockage experiment
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Dixon and jolly demonstrated the process of translocation of  water and minerals from base to apex of the plant and is known as the ascent of sap as proposed by Dixon and Jolly. The complex tissue xylem in plants is responsible for translocation water and minerals in plants. In blockage experiment, two small shoots of a woody plant are taken. Their cut ends are so prepared that in one shoot phloem is blocked with wax, while in the other xylem is blocked. Now the cut ends are submerged in water. After some time, the shoot with its xylem blocked shows wilting, but the shoot with its phloem blocked remains unaffected.