Plants having little or no secondary growth are

According to Histogen theory, the plerome gives rise to

Which one of the following has least influence on cell elongation in a meristem

The histogens are classified on the basis

Which of the following statement$(s)$ is/are true?
$(A)$ Uneven thickening of cell wall is characteristic of sclerenchyma. 
$(B)$ Periblem forms cortex of the stem and the root.
$(C)$ Tracheids are the chief water transporting elements in gymnosperms.
$(D)$ Companion cell is devoid of nucleus at maturity.
$(E)$ The Commercial cork is obtained from Quercus suber