The activity of cambium in plants is under the control of
Many physiological factors
Many environmental factors
Only water availability
Both ($a$) and ($b$)
Cambium activity is highest in
Commercially important fibres of cotton are
Select the wrong statements
$I.$ Primary and secondary phloem gets crushed during secondary growth
$II.$ During secondary growth, primary xylem remains more or less intact
Desert grasses often roll their leaves due to presence of