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

Glucose produced by photosynthesis is converted into sucrose,then moved into the companion cells and then into the living phloem sieve tube cells by........

In plants,polymerisation of excess sugar into starch takes place in the . . . . . . at the sink end.

If a stem is girdled,what happens?

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.

Consider the following statements and choose the correct option from the codes given below:
$I.$ Loading of phloem is related to the increase of sugar in phloem.
$II.$ Active loading of sugar in the sieve tube of phloem is driven by a proton pump.
$III.$ Pressure may be positive or negative in sieve tube cells.
$IV.$ Water and solutes move through the sieve tube against the pressure gradient.
$V.$ Cytoplasmic strands pass through the holes in sieve plates and form continuous filaments.