Botany and Plant Science

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'

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'.

The cells of the seive tube elements contains protoplasm. a large vacuole however nucleus is lost at maturity. The conduction of food material takes between the cells through seive plants. The flow of food (sucrose), its loading etc is controlled by companion cells. Each seive tube cell is associated with one companion cell.

Hypodermis is a distinctive layer of mechanical tissue present in some dicot and monocot stems. It is collenchymatous and present as 3-4 layers. It provides mechanical support and elasticity, also stores food.

Cortex is the outermost layer of the stem or root of the plant. It is surrounded by a parenchymatous layer. The cortex is unspecialized cells which help as conducting tissue in the plants.

Peripheral vascular bundles are generally smaller than the centrally located ones because the phloem parenchyma is absent and the water containing cavities are present in the vascular bundles which are both in monocot and dicot stem.

Most of the features of the dicot and monocot roots are similar except the vascular bundles. In the dicot root, there are 2-6 bundles of xylem and phloem alternating whereas in monocots the number of xylem and phloem strands are more than 8. Further, the xylem vessels in dicots are polygonal and those of monocots are oval.

• In dicot stem, the secondary vascular tissues originate as a result of the cambial activity. 
• The cambial cells divide tangentially again and again and produce secondary tissues. 
• Some of the cells of single-layered pericycle become meristematic, which divides and form a few layers of cells, phellogen.
• Hence, In a dicot stem, pericycle gives rise to Phellogen.
• So, the correct answer is 'Phellogen'.

Phellem is outermost layer of cork cambium, which is suberised. Hence, this is the first layer to be found. 
Endodermis is one the layer of cortex, which is to be found under the phellem.
Pericycle is the layer present between endodermis and vascular bundles. 
Dicotyledonous stem possess conjoint, collateral vascular bundle, where xylem is internal and phloem is external. Therefore, phloem is to be encountered after the pericycle. Hence, option C is correct. 

Dicot stem hypodermis is a region lying immediately below the epidermis. It is represented by a few layers of collenchyma cells with angular thickenings. The cells are compactly arranged without any intercellular spaces. Hypodermis provides mechanical support and additional protection. 

Dicot stem vascular bundles are eight in number, arranged in form of a broken ring. The vascular bundles are conjoint, collateral and open. Xylem is on the inner surface and phloem on the outer surface. Xylem is described as endarch. 

In dicot stem, hypodermis is a region lying immediately below the epidermis. It is represented by a few layers of collenchyma cells with angular thickenings. The cells are compactly arranged without any intercellular spaces. Hypodermis provides mechanical support and additional protection. Phellogen is the secondary lateral meristem that may arise from permanant living cells of hypodermis or outer cortex. It is composed of single layer of meristematic cells. 

Dicot stem vascular bundles are eight in number, arranged in form of a broken ring. The vascular bundles are conjoint, collateral and open. Xylem is on the inner surface and phloem on the outer surface. Xylem is described as endarch.