Which structure of the phloem creates a pressure gradient in the sieve tube?

Explain the pressure flow hypothesis of translocation of sugars in plants.

Spanner and Jones suggested which of the following methods for translocation through phloem?

The bimodal theory of translocation was put forth by

What is correct for $P$ in the given diagram representing the pressure flow hypothesis?

The radio-labelled carbon in carbon dioxide supplied to potato plants in an experiment was eventually seen in the tuber. Trace the movement of the labelled carbon dioxide.