Auxins inhibit the growth of

In plants,lower branches are larger than upper branches due to . . . . . . .

Which of the following hormones is a weak organic acid having unsaturated ring structures and is derived from an amino acid?

$A$ : Auxin treatment causes acidification of the cell wall and helps in cell elongation.
$R$ : Loosening of cell wall microfibrils occurs.

Give scientific reasons: Auxins fail to enhance the growth of intact plants.

What is the direction of transport of $Auxin$?