Question

32. According to Munch's pressure flow hypothesis, the main driving force for transport
of organic solutes in the phloem tissue from source to sink is:
when
(A) Concentration gradient
doesn't
ough
Occurs
(B) Osmotically generated pressure gradient
(C) Diffusion pressure deficit
(D) Energy through hydrolysis of ATP
​

Answer 1

Answer:

Explanation:

Mass flow hypothesis or pressure flow hypothesis to explain translocation was given by Munch, 1930. According to this theory organic substances move in the sieve tubes from the region of high osmotic concentration to the region of low osmotic concentration in a mass flow due to occurrence of pressure gradient. The osmotic concentration remains high in the mesophyll cells due to the process of photosynthesis and photosynthates are actively loaded by them in the phloem tissue.  

Similarly at the sink end, the photosynthates are actively unloaded for utilisation. This is the most widely accepted theory to explain translocation in plants.