Tag: plant physiology
Questions Related to plant physiology
The earliest undoubled vascular plants are found in the rocks of ______________.
-
Early Cambrian
-
Early Devonian
-
Mid-creataceous
-
Not until the beginning of Quaternary
Choose the correct answer from the alternatives given.
Minerals enter a plant mainly by:
-
diffusion
-
pressure flow
-
translocation
-
active transport
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?
-
Xylem
-
Phloem
-
Both of the above
-
None of the above
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
-
Passive water absorption
-
Active water absorption
-
Conditions favouring transpiration
-
Conditions restricting transpiration
- 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
-
Epidermis
-
Xylem
-
Phloem
-
Pith
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
-
McDermott
-
MacDougal
-
Crammer
-
None of the above
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
-
Cohesion among water molecules
-
Strong transpiration pull
-
Adhesion
-
Surface tension
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:
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.
Which one explains ascent of sap ?
-
Cohesion-tension theory of Dixon and Joly
-
Starch-sugar interconversion
-
Photosynthesis
-
None of the above
Most widely accepted theory of carbohydrate translocation is
-
Mass flow theory
-
Root pressure theory
-
Imbibition theory
-
Transpiration theory
(A) Mass flow theory proposes the transportation of food in the plants.
Munch hypothesis is based on translocation of food due to
-
Imbibition force
-
Turgor pressure (TP) gradient
-
Both A and B
-
None of these
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.