Question

In dicot root showing secondary growth, cork is found

• A. External to primary cortex
• B. Inner to epidermis and outer to pericycle
• C. Outer to endodermis and inner to primary cortex
• D. Inner to endodermis and external to primary phloem

Answer 1

The correct option is B Inner to epidermis and outer to pericycle

During secondary growth, rupturing of epidermal cell and outer cortex by secondary tissues induces formation of new protective layer, periderm turning the single layered pericycle into multi layered meristem that divides to form cork cambium or phellogen. The cork cambium exhibit meristematic activity and produces cork or phellem towards the periphery and phelloderm on inside, i.e., extrastellar growth. Moving from centre to periphery, a dicot root has pith, secondary xylem, secondary phloem, phelloderm (secondary cortex), phellogen (cork cambium), cork (phellem) and bark. Since, primary cortex is ruptured and is not present in secondary root. Cork is extra stellar tissues which is present outside the stele (vascular bundle, pith and medullary rays surrounded by pericycle) region and hence, cannot be present inner to endodermis.
Thus, the correct answer is option B.