Tag: botany

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.

The parenchyma in the centre is called as the pith. The term stele included the vascular system, associated tissues and the pith. The protostele is a simple, unbranched, centrally located axial strand of xylem interspersed with phloem. A protostele contains no pith. It is generally found in dicot stems and in most angiosperm monocot roots.

The hypodermis is found below the epidermis in dicot stem and is constituted with angular collenchyma which is 3-5 layered. Pericycle consists of alternately arranged patches of sclerenchyma and parenchyma. 
Thus, the correct answer is option C.

A. Periderm - During secondary growth in both dicot stem and root, multilayered or cellular complex tissue formed in the region of cortex is called Periderm. It is formed towards the outer side of the stem or root.

B.Epiblema – Epidermis with root hairs is called Epiblema.

C. Phelloderm – the parenchymatous formed towards inner side of the cork cambium is called phelloderm or secondary cortex.

D. Phellogen – a ring of meristematic tissue formed by the dedifferentiation of parenchyma present in the general cortex of dicot stem or root is called Phellogen or cork cambium.

So, the correct option is ‘Periderm’.

In the vascular bundles of Cucurbita stems, a xylem strand and two phloem strands are present on the same radius. So the vascular bundles are called Bicollateral vascular bundles. In these bundles, two strips of cambiua are present in between the xylem and phloem.

So, the correct option is ‘ 2’.

In dicot stem, during secondary growth, when new secondary xylem formation is going on, oldest secondary xylem appear outside the primary xylem.

The layer with thick walled present around the vascular bundles is called Bundle sheath. It is sclerenchymatous in monocot stem vascular bundles, parenchymatous in dicot leaf and monocot leaf. It is absent in vascular bundles of dicot stem

So, the correct answer is ‘Dicot stem’

A.Helianthus - a dicot with rings of vascular bundles in the stele. It is called Eustele.

In dicot stem, endodermal cells are rich in starch grains. So it is also called endodermoid layer or starch sheath or starch layer.

So, the correct option is ‘Starch sheath’.