Category: Biology Second Paper

The green ground tissue in leaves is called mesophyll tissue. There are two types of mesophyll tissue.
1. Palisade parenchyma: Palisade parenchyma cells are long, densely packed, non-vesicular and vertically arranged.
2. Spongy parenchyma: Spongy parenchyma cells are round, thin, fibrous and loosely arranged.
Function: Mesophyll tissue produces food through the process of photosynthesis.5. Water sac: Water accumulates in the skin cells of ice plants and takes the form of a sac. In winter this water turns into ice. For example, Mesembrayanthemum crystallinum.

The green ground tissue in leaves is called mesophyll tissue. There are two types of mesophyll tissue.
1. Palisade parenchyma: Palisade parenchyma cells are long, densely packed, non-vesicular and vertically arranged.
2. Spongy parenchyma: Spongy parenchyma cells are round, thin, fibrous and loosely arranged.
Function: Mesophyll tissue produces food through the process of photosynthesis.5. Water sac: Water accumulates in the skin cells of ice plants and takes the form of a sac. In winter this water turns into ice. For example, Mesembrayanthemum crystallinum.

The part from medulla to pericycle through the vascular bundle is called medullary ray. It is composed of narrow and elongated parenchyma cells. The medulla is found in the stems of dicotyledonous plants.

The part surrounded by vascular bundles located in the center of root and stem is called marrow. It is composed of parenchyma or sclerenchyma cells. The cells are spherical, thin-walled, and capsuled. It originates from the ground tissue. The medulla is absent in the roots of dicotyledonous plants. Many times the medulla is destroyed in the center of the root and stem and creates voids. It is called lysigenous cavity. Stems of pumpkin, papaya, bamboo, cucumber etc. contain lysigenous.
Function of medulla: It stores food. Sclerenchymaske¬renchyma gives the plant strength.

One or more layers of pericycle under endoderm. It is composed of parenchyma or scarenchyma or both tissues. Sclerenchyma tissue sits like a cap on top of the phloem. It is called Bundle cap. Pumpkin and sunflower stems have hard busts. Pericycles are present in the roots and stems of pteridophytes and in the roots of flowering plants. In the stems of pumpkin and kumarica plants, the pericycle is multi-layered and composed of scarenchyma tissue. It is absent in parasites and aquatic plants. In modern concepts, the pericycle is part of the phloem.
Function of pericycle: It produces apical roots in the stem. It gives strength to the plant. It stores food. It creates side roots.

The region from the pericycle to the pith in the center of the root and stem is called the stilt or intrastilt zone. Its various parts are-
(i) Pericycle: One or more layers of pericycle under endoderm. It is composed of parenchyma or scarenchyma or both tissues. Sclerenchyma tissue sits like a cap on top of the phloem. It is called Bundle cap. Pumpkin and sunflower stems have hard busts. Pericycles are present in the roots and stems of pteridophytes and in the roots of flowering plants. In the stems of pumpkin and kumarica plants, the pericycle is multi-layered and composed of scarenchyma tissue. It is absent in parasites and aquatic plants. In modern concepts, the pericycle is part of the phloem.
Function of pericycle: It produces apical roots in the stem. It gives strength to the plant. It stores food. It creates side roots.
(ii) Medulla : The part surrounded by vascular bundles located in the center of root and stem is called marrow. It is composed of parenchyma or sclerenchyma cells. The cells are spherical, thin-walled, and capsuled. It originates from the ground tissue. The medulla is absent in the roots of dicotyledonous plants. Many times the medulla is destroyed in the center of the root and stem and creates voids. It is called lysigenous cavity. Stems of pumpkin, papaya, bamboo, cucumber etc. contain lysigenous.
Function of medulla: It stores food. Sclerenchymaske¬renchyma gives the plant strength.
(iii) Medullary ray: The part from medulla to pericycle through the vascular bundle is called medullary ray. It is composed of narrow and elongated parenchyma cells. The medulla is found in the stems of dicotyledonous plants.
Function of marrow: It stores water and food. Transports water and food. It forms secondary tissue.

Vascular bundles and other cells act as a barrier to the endodermis by entrapping air and water to prevent obstruction. It protects the inner part. It stores food. It controls the root pressure.

The inner layer of cortex is called endodermis. It is composed of single-layered and barrel-shaped cells. The cells are densely packed and without gaps. Suberin and lignin accumulate in the inner walls of the cells to form a ribbon-like lining. This is called the Caspian strip. It is named after the scientist Caspery (1865). Endothelial cells that have thin walls are called passage cells or passage cells. The endodermis of the stem of dicots (sunflowers) contains many starchy grains called starch sheath. Stems of monocots do not have endosperms.

The part from below hypodermis to endodermis is called cortex. It is multilayered and composed of parenchyma cells. Cells are round and have intercellular spaces. It contains scarides, oil glands and resin ducts.
Functions: Cortex stores water and food, gives strength to the plant and participates in photosynthesis. It controls the root pressure. Shvetsar stores food.

One or more cell layers under the skin is called hypodermis. Hypoderm is absent in plant roots. It is formed by skerenchyma cells in monocots and collenchyma cells in dicots.
Action: Strengthens and protects the stem.