Aerenchyma is found in

In which of the sieve tubes are the callose plugs formed?

All the following statements regarding sieve tube elements are true except

Sieve tubes are better suited for translocation,because

Cells of permanent tissue are $...........$.

$I.$ Made up of sclerenchymatous cells
$II.$ Generally absent in primary phloem
$III.$ Much elongated and pointed
Given above characters belong to which of the following?