Who proposed that the upward and downward movement of materials takes place through the phloem?

According to the pressure flow hypothesis:
$A.$ Phloem loading produces a hypertonic condition in the sieve tubes.
$B.$ Water potential gradient facilitates the mass movement in the phloem.
$C.$ Phloem unloading is a passive process.

The transport of food in phloem is:

What is the primary substrate for the translocation of food in plants?

What is the direction of movement of sugars in phloem?

Transport of different types of solute substances takes place by