Tag: theories of translocation

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

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

  1. Xylem

  2. Phloem

  3. Both of the above

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

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

The cohesion transpiration pull theory operates only in

  1. Passive water absorption

  2. Active water absorption

  3. Conditions favouring transpiration

  4. Conditions restricting transpiration
Reveal answer Fill a bubble to check yourself
C Correct answer
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'.
Multiple choice botany plant physiology mineral absorption transport of food, water and minerals mineral transport theories of translocation transport in the phloem of plants

In plants the translocation of organic solutes take place through

  1. Epidermis

  2. Xylem

  3. Phloem

  4. Pith
Reveal answer Fill a bubble to check yourself
C Correct answer
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. 

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

Dendrograph was discovered by

  1. McDermott

  2. MacDougal

  3. Crammer

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

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

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

  1. Cohesion among water molecules

  2. Strong transpiration pull

  3. Adhesion

  4. Surface tension
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

Which one explains ascent of sap ?

  1. Cohesion-tension theory of Dixon and Joly

  2. Starch-sugar interconversion

  3. Photosynthesis

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
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'.
Multiple choice botany plant physiology mineral absorption transport of food, water and minerals mineral transport theories of translocation transport in the phloem of plants

Most widely accepted theory of carbohydrate translocation is

  1. Mass flow theory

  2. Root pressure theory

  3. Imbibition theory

  4. Transpiration theory
Reveal answer Fill a bubble to check yourself
A Correct answer
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'.

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

Munch hypothesis is based on translocation of food due to

  1. Imbibition force

  2. Turgor pressure (TP) gradient

  3. Both A and B

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
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'.

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

Mass flow hypothesis was first described by ___________.

  1. Swanson

  2. Buchman

  3. Kursanov

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

Mass flow or pressure flow hypothesis was put forward by Munch $(1927, 1930)$. According to this hypothesis, organic substances move from the region of higher osmotic pressure to the region of lower osmotic pressure in a mass flow due to the development of a gradient.

So, the correct answer is 'Munch'

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

Presence of bicollateral vascular bundle provides evidence that conduction of food takes place through the

  1. Phloem

  2. Xylem

  3. Both A and B

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

Translocation of prepared food occurs through the phloem. Bicollateral vascular bundles have two patches of phloem. Bicollateral vascular bundles show following arrangement of vascular tissue, outer phloem, outer cambium, xylem, inner cambium, inner phloem. These vascular bundles can transport much more amount of sugars than collateral vascular bundles having only a single patch of phloem. Bicollateral vascular bundles are common in Family Cucurbitaceae with large leaves, large fruits called Pepo and thin weak stems.