After achieving its maximum,the growth decreases slowly during the phase of

Sleep movements of leaves in certain plants or photonasty is due to:

When growth is exemplified by a root elongation at a constant rate,mathematically,it is expressed as:

During the cell enlargement phase of growth,molecules of new cell wall material are inserted between the original molecules of the stretched wall. This process is known as:

The phase of maturation is characterised by:
$I.$ Cells attaining their maximal size
$II.$ Proper wall thickening and protoplasmic modification
$III.$ Rapid cell division
Select the correct option.

Length of the stem at time $0$ is $20 \ cm$. The arithmetic growth rate is $30 \ cm$ per day. What is the length of the stem at the end of the $7^{th}$ day (in $cm$)?