Category: Biology Second Paper

The region outside the stellar is called the outer stellar region. Its various parts are-
(i) Hypodermis: 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.
(ii) Cortex: 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.
(iii) Endodermis: 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.
Functions of Endodermis: 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.

Other than epidermal and vascular tissues, the tissues forming the other parts of the plant body are called ground tissues. Most plant tissues are ground tissues. It is composed of parenchyma tissue. However, collenchyma and scherenchyma tissue can also be formed. This tissue system originates from periosteum dividing tissue. In the roots of all plants and in the stems of dicotyledonous plants, the ground tissue system is divided into two regions. Exosteal region and intraosteal region.

Other than epidermal and vascular tissues, the tissues forming the other parts of the plant body are called ground tissues. Most plant tissues are ground tissues. It is composed of parenchyma tissue. However, collenchyma and scherenchyma tissue can also be formed. This tissue system originates from periosteum dividing tissue. In the roots of all plants and in the stems of dicotyledonous plants, the ground tissue system is divided into two regions. Exosteal region and intraosteal region.
1. Extra stellar region
The region outside the stellar is called the outer stellar region. Its various parts are-
(i) Hypodermis: 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.
(ii) Cortex: 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.
(iii) Endodermis: 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.
Functions of Endodermis: 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.
2. Intrastellar region
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.

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.

(i) Water passes through the hydathode in liquid form.
(ii) There is a water chamber below it. Water accumulates there.
(iii) Hydathodes are more active at night than during the day.
(iv) Hydathodes cause water droplets to appear on leaf edges in the morning.
(v) Salts are released during water evaporation.
(vi) Water excretion is high when perspiration is low.

The cells that make up the hydathode are called epithems. Aqueducts are made up of a bunch of living cells. Cells are watery and have intercellular spaces. The cells do not have chloroplasts. Each hydathode has one or more pores. Its pore is structurally similar to a leaf pore. But somewhat large in size and unable to move. It consists of one or more chambers. The chambers open into windpipe or trachea.

The pores located along the edges of plant leaves through which water is released in liquid form are called hydathodes. The release of water in liquid form is known as gation or water excretion or water drinking. Hydathodes are more active at night than during the day. Hydathodes are located along the edges of plant leaves. That’s why in the morning water is seen on the edges of the leaves. Hydathodes are present in plants like grasses, squash, tomato, saffron, strawberry, primula, rose, balsam, Ranunculus fluitans, Campanula rotundifolia. Hydathods named Esau in 1965.

(i) In the process of photosynthesis, the raw material for making food, carbon dioxide, enters the cell through the stomata. Sugars are produced from carbon dioxide. Plants with more leaves have more stomata. Due to this, the supply of carbon dioxide increases and food production increases.
(ii) Water is an important raw material in the process of photosynthesis. In the transpiration process, excess water is released through the stomata in the evapotranspiration. As a result water flow is created and water enters different cells. This water is used in the process of photosynthesis. (iii) After making food in the process of photosynthesis, oxygen released as a by-product escapes through the stomata. Oxygen is an essential element in photosynthesis. It reduces the rate of photosynthesis. Food production is accelerated when oxygen escapes through the stomata.
(iv) Each stomata contains two guard cells. The guard cell contains a large number of chloroplasts. This chloroplast produces food in the process of photosynthesis.
(v) Green accessory cells surround the stomata. Chloroplasts of accessory cells take part in the process of photosynthesis to make food.

(i) Photosynthesis: The biochemical process by which green plants produce sugary food by chemically combining water and carbon dioxide with the help of chlorophyll in the presence of sunlight and releasing oxygen as a by-product is called photosynthesis. Carbon dioxide needed for photosynthesis enters the cell through the stomata. Carbon dioxide reacts with water to form sugars and release oxygen as a byproduct. Oxygen is released out of the cell through the stomata. Therefore, stomata play an important role in carrying out the process of photosynthesis.
(ii) Respiration : The biochemical process in which respired matter is completely oxidized in the presence of free oxygen to produce water, CO2 and energy is called respiration. Oxygen required for plant growth enters the cells through the stomata. Oxygen reacts with oxygen to produce water, CO2 and energy. The carbon dioxide produced is released out of the cell through the stomata. Therefore, stomata play an important role in carrying out the reproductive process.
(iii) Transpiration: The process by which the excess water absorbed by the roots of the plant evaporates through the stomata is called transpiration. Green plants use only 1-2% of the water absorbed by their roots. The remaining 98-99% of water is useless. Excess water is released by evaporation through the stomata. Therefore, stomata play an important role in carrying out the process of respiration.
(iv) Temperature regulation: A lot of heat is generated as a result of various biological processes in the plant body. During respiration, heat is released through the stomata. If the heat wasn’t released outside, the plant would burn to death.
(v) Gaseous exchange: It involves the exchange of gaseous substances or O2 and CO2.
(vi) Opening and closing of stomata : Guard cells control the opening and closing of stomata.
(vii) Synthesis and storage of organic food: Glucose is synthesized in the guard cells and temporarily stored as glucose.

The leaf pores are hidden deep in the skin. This is called hidden or submerged stomata. The stomata are open during the day and closed at night. However, the stomata of Patharkuchi plants are closed during the day and open during the night. The plant’s stomata are fully open from 10-11 am and 1-3 pm.