Question

In which of the following order, an exarch xylem develops?
a. Centripetal
b. Centrifugal
c. Both centripetal and centrifugal
d. Irregular

Answer 1

Hint: Xylem is a tissue in the plant. It is used to carry water and nutrients throughout the plant. The xylem can be exarch, centrarch, mesarch or endarch.

Complete answer:
Xylem is a plant tissue which is used to carry water and nutrients into the plant. The xylem can be exarch or endarch according to the development. It can also be centrarch or mesarch.

Whenever there is more than a single strand of primary xylem in a root or stem an exarch is used. The xylem has a tendency to develop from outside towards the centre in other words centripetal.

Hence, the protoxylem lies closest to the peripheral area and the metaxylem lies nearest to the central region. The plants which tend to have high vascularity undergo exarch development.

Whenever there is more than a single strand of primary xylem in a root or stem and the xylem has a tendency to develop from inside to outside, it undergoes endarch development. In other words it grows centrifugally.

Whenever there is more than a single strand of primary xylem in stem or root and it grows from the middle portion towards both the directions it is a metaxylem.

Hence, the correct answer is option (A).

Note: Centripetal is defined as growth and development from outside towards the centre. This is seen in research. Centrifugal is defined as growth and development from inside to outside. This is seen in research. Endarch is seen in the stems of dicot and monocot plants.