Aerenchyma is helpful in plants by

Contractile tissues have the following features
$(i)$ Mesodermal in origin
$(ii)$ They contain stretch receptors.
$(iii)$ Rhythmic contractions are seen in them
$(iv)$ They do not fatigue during the life of the animal
Which of the above are characteristics of sphincters?

The layer of cells outside the phloem meant for giving rise to the root branches is called