Tag: plant physiology

Questions Related to plant physiology

The earliest undoubled vascular plants are found in the rocks of ______________.

botany plant physiology mechanism of absorption mineral absorption significance of transpiration transport of food, water and minerals mineral transport

  1. Early Cambrian

  2. Early Devonian

  3. Mid-creataceous

  4. Not until the beginning of Quaternary

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Correct Option: A

Choose the correct answer from the alternatives given.
Minerals enter a plant mainly by:

botany plant physiology mechanism of absorption mineral absorption significance of transpiration transport of food, water and minerals mineral transport

  1. diffusion

  2. pressure flow

  3. translocation

  4. active transport

Show answer
Correct Option: D
Explanation:

Active transport is a process that is required to move molecules against a concentration gradient. For plants to take up mineral ions, ions are moved into root hairs, where they are in a higher concentration than in the dilute solutions in the soil. So, the correct answer is "Active Transport".

Which of the tissue is more important for translocation of sucrose?

botany plant physiology mineral absorption transport of food, water and minerals mineral transport theories of translocation transport in the phloem of plants

  1. Xylem

  2. Phloem

  3. Both of the above

  4. None of the above

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Correct Option: B
Explanation:

Translocation of organic nutrients from the region of source or supply to the region of sink or utilisation is mostly in the form of sucrose. Phloem (sieve tubes or sieve cells) is the pathway for this translocation, as found put by stem girdling, sieve tube puncturing, radioautography and chemical analysis of sieve tube sap.

The cohesion transpiration pull theory operates only in

botany plant physiology mineral absorption transport of food, water and minerals mineral transport theories of translocation transport in the phloem of plants

  1. Passive water absorption

  2. Active water absorption

  3. Conditions favouring transpiration

  4. Conditions restricting transpiration

Show answer
Correct Option: C
Explanation:
  • The cohesion-tension theory is a theory of intermolecular attraction that explains the process of water flow upwards (against the force of gravity) through the xylem of plants. 
  • Transpiration pull, utilizing capillary action and the inherent surface tension of water, is the primary mechanism of water movement in plants. 
  • Hence, The cohesion transpiration pull theory operates only in Conditions favouring transpiration.
  • So, the correct answer is 'Conditions favouring transpiration'.

In plants the translocation of organic solutes take place through

botany plant physiology mineral absorption transport of food, water and minerals mineral transport theories of translocation transport in the phloem of plants

  1. Epidermis

  2. Xylem

  3. Phloem

  4. Pith

Show answer
Correct Option: C
Explanation:

In vascular plants, water and minerals move through xylem, whereas sugars move through phloem. Ringing experiments prove that sugars move through phloem. If the phloem tissue is removed in a ring or girdle, the sugars cannot be transported to roots from aerial parts and plant dies. 

Dendrograph was discovered by

botany plant physiology mineral absorption transport of food, water and minerals mineral transport theories of translocation transport in the phloem of plants

  1. McDermott

  2. MacDougal

  3. Crammer

  4. None of the above

Show answer
Correct Option: B
Explanation:

Dixon explained ascent of sap in trees based on transpiration, cohesion, adhesion theory. Mac Dougal supported transpiration pull theory through experimental proof. Cohesive force and adhesive force works continuously in the cavity (lumen) of xylem. Both the forces are responsible for maintaining unbroken continuity of water column from the roots to the leaves.

A rising column of water does not break its connection in the xylem vessels, despite negative pressure or tension due to

botany plant physiology mineral absorption transport of food, water and minerals mineral transport theories of translocation transport in the phloem of plants

  1. Cohesion among water molecules

  2. Strong transpiration pull

  3. Adhesion

  4. Surface tension

Show answer
Correct Option: A
Explanation:

Cohesion-Tension or Cohesion Transpiration pull theory was put forward by Dixon and Jolly in 1894. It is also known as Dixon's theory of Ascent of Sap. The important points are: 

1. Cohesion (attractive force between water molecules) and Adhesion (attractive force between water and xylem channels) Forces.
2. Continuous water columns.

3. Transpiration pull.
Water molecules are held together by strong cohesion force which is due to hydrogen bonds amongst them. It is due to these forces that water forms a continuous column in xylem elements. If there is an air bubble or air gap in this continuous column then water will not rise in the xylem elements. This break in rise of water is called as cavitation.

Thus, the correct answer is option A.

Which one explains ascent of sap ?

botany plant physiology mineral absorption transport of food, water and minerals mineral transport theories of translocation transport in the phloem of plants

  1. Cohesion-tension theory of Dixon and Joly

  2. Starch-sugar interconversion

  3. Photosynthesis

  4. None of the above

Show answer
Correct Option: A
Explanation:
(A)Cohesion transpiration pull theory proved that cohesion and adhesion support continuity of water columns and provide strength like a steel wire, transpiration pulls water columns towards leaves which causes ascent of sap.
(B)Starch sugar theory was given by Steward proposing that during daytime enzymes phosphorylase and converts starch into sugar increasing the osmotic potential causing ascent of sap.
(C)Photosynthesis is the process of formation of complex compounds, glucose using simple compounds like carbon dioxide, sunlight.
So, the correct answer is 'Cohesion-tension theory of Dixon and Jolly'.

Most widely accepted theory of carbohydrate translocation is

botany plant physiology mineral absorption transport of food, water and minerals mineral transport theories of translocation transport in the phloem of plants

  1. Mass flow theory

  2. Root pressure theory

  3. Imbibition theory

  4. Transpiration theory

Show answer
Correct Option: A
Explanation:

(A) Mass flow theory proposes the transportation of food in the plants.

(B) Root pressure theory proposes the transportation of water in the plants through the root pressure.
(C) Imbibition theory proposes water transportation through pipes.
(D) Transpiration theory proposes water transportation due to the evaporation from the upper surface of the leaves.
So, the correct answer is 'Mass flow theory'.

Munch hypothesis is based on translocation of food due to

botany plant physiology mineral absorption transport of food, water and minerals mineral transport theories of translocation transport in the phloem of plants

  1. Imbibition force

  2. Turgor pressure (TP) gradient

  3. Both A and B

  4. None of these

Show answer
Correct Option: B
Explanation:

Munch hypothesis is also called the pressure flow hypothesis, it explains the movement of sap through the phloem. It proposed by Ernest Munch in 1930. High concentration of organic substance inside the cell of the cells of the phloem at a source that creates the diffusion gradient drawing water from the adjacent xylem resulting into the turgor pressure.

So, the correct answer is 'Turgor pressure gradient'.