Tag: internal structure of root, stem and leaf

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’.

The corky outer layer of a plant is commonly called the periderm. It has three parts- the cork cambium (phellogen), the cork (phellem), and the secondary cortex (phelloderm). It usually forms as a result of secondary thickening in the case of an injury.

• In vascular plants, the secondary growth occurs due to the activity of the two lateral meristems- the cork cambium and the vascular cambium.
  
• In woody plants, the secondary growth produces wood and gives shapes to the plant with a thickened trunk.
• The secondary growth develops a cork cambium and vascular cambium.
• The cork cambium forms the thickened cork cells which protect the surface of the plant and also reduces water loss.
• Vascular cambium is also known as fascicular cambium which develops within the vascular bundles that produce xylem to the inner side and phloem to the outer side.
• In dicots, the fascicular and interfascicular cambium combine together to form a continuous ring called the vascular cambium.
• So, the correct answer is 'Lateral meristem'

Secondary growth occurs due to cell division in cambia or lateral meristems resulting in thickening of stems and roots. This is the characteristic feature of dicotyledons, gymnosperms and vascular system plants. Teak and pine belong to these systems and study of secondary growth is possible in these plants.

Epiblema is the outer layer of the roots also known as epidermal cells of roots which perform the function of absorption.

1. Cucurbita stem: Collenchyma is the tissue of primary body. The cell walls show localized thickenings. It occurs chiefly in the hypodermis of dicot stems( e.g. Cucurbita, Helianthus).
   2. Potato tuber: Parenchyma is cell and tissue type in which the cells have only thin primary walls. The cotyledon of many leguminous plants contains protein and starch in their parenchyma cells. Protein and starch are present in the parenchyma of potato tuber.
   3. Walnut shell: Sclerenchyma consists of thick-walled dead cells. It usually occurs in hard parts of plant bodye.g. hard endocarp of Walnut, almond and coconut).
   4. Jute fibres: Phloem fibres are also called bast fibres and most occur in secondary phloem. The fibres of primary phloem have both cellulose and lignified thickenings.
   So, the correct answer is 'Collenchymatous hypodermis, Parenchyma, Sclerenchyma, Phloem'.