After two or three years of the secondary growth, the cortex in dicot root

Assertion : In woody stems, the amount of heart wood continues to increase year after year.
Reason : The cambial activity continues uninterrupted

Late wood is formed during autumn season.

Cambium activity is highest in

Vascular cambium is a meristematic layer that cuts off

$I.$ It is resistant to microorganisms

$II.$ It comprises dead elements

$III.$ It comprises highly lignified cell wall

$IV.$ It is the peripheral part

$V.$ It is dark and tough

Which of the above property doesn't belongs to heart wood?