The movement of materials through the vascular tissue of plants is called

The following figure illustrates the pressure-flow hypothesis. Which of the following represents the source?

Arrange the following events of mass flow of organic material in sequence:
$I$. Sugars are transported from cell to cell in the leaf
$II$. Food is synthesized in form of glucose by leaf cells
$III$. Movement of water takes place into sieve tube elements
$IV$. Downward movement of sugar occurs in the stem
$V$. Solutes are actively transported into the sieve elements

The supply ends in the transport of solutes are:

Bidirectional elements transportation is seen in:

Mass flow hypothesis was first described by