Category: Biology Second Paper

Permanent tissue is divided into three parts. Simple tissue, complex tissue and secretory tissue.
Simple tissue
A permanent tissue whose cells have the same size, shape and structure is called simple tissue. Simple tissue is divided into three parts. These are-
1. Parenchyma: The length, width and depth of the tissue cells are almost the same is called parenchyma. Cells are concentric and round, ovoid, multilobed or oblong. Intercellular spaces exist. Parenchyma tissue consists of stem and root skin, cortex, pith, medulla, pericycle, leaf mesophyll, fruit shell, seed and embryo.

Functions of parenchyma tissue
(i) Chlorophyll-containing parenchyma (chlorenchyma) produces food in the process of photosynthesis.
(ii) Parenchyma of aquatic plants holds air deposits (arenchyma) and helps the plant to float.
(iii) Lower stems, roots, fruits and seeds contain sugars, proteins and carbohydrates.
(iv) Helps in plant wound healing and regeneration.
(v) Provides strength to leaves and stems.
(vi) Stamens keep the plant upright by hydrostatic pressure.
(vii) Propagation by asexual roots and shoots.
(viii) Tissues containing xylem and phloem transport water and mineral salts.
2. Collenchyma: Collenchyma consists of living cells without lignin, having thick walls. Cells are multilobed or elongated. There are no intercellular spaces. Cells are proliferative.
Functions of collenchyma tissue
(i) Collenchyma containing chloroplasts (chlorenchyma) produces food.
(ii) Provides mechanical strength to growing and soft organs of plants.
(iii) Helps plants to bend due to elastic and extensible properties.
(iv) Plant organs do not break easily as they are elastic.
3. Sclerenchyma: Sclerenchyma consists of lignin-rich, thick-walled cells. The transformed cells are dead and do not contain protoplasm. There are no intercellular spaces. Cells are tough and elastic. Cells are longer than wide.
Functions of Sclerenchyma Tissue
(i) Provides mechanical advantage to plants.
(ii) Protects the plant from various environmental stresses and strains.
(iii) Contains waste material in the dead state.
(iv) Protects soft parts of fruits and seeds.
(v) Transports little water.

1. The cells are non-dividing and reside in the stationary zone of the plant.
2. The cytoplasm of the cell is thin.
3. Cell nucleus is relatively small.
4. Cells are living or dead and asymmetric.
5. Cells are irregular in shape.
6. Their cells have cell cavities.
7. They have intercellular spaces.
8. Cells have a low metabolic rate.
9. Various designs are seen in cells.
10. Their cell walls are thick and made of lignin and pectin.

A tissue whose cells are unable to divide is called permanent tissue. Divisive tissue becomes permanent tissue when its ability to divide is suspended. For example- xylem, phloem etc.

1. Zygote Development: Dividing tissue divides to form sperm and egg. A zygote is formed by the union of sperm and egg. A zygote is a type of dividing tissue and is the first cell in an organism.
2. Embryo Development: The zygote divides repeatedly to form a multicellular embryo. Embryo is composed of dividing tissue and dividing cells. It is an important stage in the body formation of organisms.
3. Seedling Development: The embryo divides repeatedly to form a seedling plant. Seedlings have roots, stems and leaves.
4. Development of complete plant: The dividing tissue of the root, stem and leaves of the seedling plant divides repeatedly to form a complete plant. The dividing tissue of the whole plant divides to form different organs.

1. Elongation: The plant grows in length by division of apical dividing tissue. It increases the physical growth and height of the plant.
2. Increase in diameter: Lateral dividers increase the diameter of dicotyledonous plants by tissue division. Dicotyledonous plants are thicker and gain mechanical strength.
3. Organ Growth: Dividing tissue leads to organ growth. As a result, the number of branches, leaves, flowers and fruits of the plant increases.
4. Wound healing: When a wound occurs in any part of the plant, dividing tissue divides and fills the wound.
5. Formation of permanent tissue: Permanent tissue is formed from dividing tissue. Dividing tissue loses the ability to divide and becomes permanent tissue.
6. Metabolism: Divided tissues carry out metabolism in the plant body. Plants with a higher amount of dividing tissue also have a higher metabolic rate. As a result, plant growth is accelerated.
7. Increase in crop yield: In crop plants, dividing tissue divides to produce flowers and fruits. This tissue divides and enlarges the fruit and seed size. Due to this the crop yield increases.

Different scientists have expressed different theories about the origin of tissue. However, according to many scientists, all tissues originate from the apical dividing tissue. The dividing tissue located at the tip of plant roots, stems and branches is called apical dividing tissue. Dissection of plant roots and stem tips reveals no tissue other than dividing tissue. Again, if it is dissected a little behind it, apart from dividing tissue, other tissues such as skin, hypodermis, cortex, pericycle, vascular bundle, marrow, marrow etc. are found. From this it can be understood that these tissues have evolved from the dividing tissue at the apex. So it can be said that all tissues originate from the apical meristem.

1. Promeristem: The early dividing tissue originates from the root and apical region of the stem of the plant. It increases root and stem length.
2. Primary meristem: Primary meristem tissue originates in the embryonic stage of the plant. It is eternally divisible. It is located at the tips of roots, stems and branches and increases the length of the plant.
3. Secondary meristem: Secondary meristem tissue originates from permanent tissue. It causes secondary growth of plants.
4. Rib meristem: Rib meristem divides into a single layer. It forms the pith of plants.
5. Plate meristem: Plate meristem is divided into two layers. It forms the scaly bark and leaves.
6. Mass meristem: Mass dividing tissue divides into all layers. It is randomly arranged to form cell islands. It gives rise to embryo, follicle, endosperm, cortex, medulla etc.
7. Apical meristem: The apical meristem is located at the apex of plant roots and stems. It divides and causes the plant to grow in length.
8. Lateral meristem: Lateral meristem tissue is located longitudinally along the sides of the root and stem of the plant. It causes secondary growth. It increases the height or width of the plant.
9. Intercalary meristem: The intercalary meristem lies between two permanent meristems. It forms the root, midrib, apex and flower bud of the plant.
10. Protoderm: Protoderm forms the epidermis and epiderm of plants.
11. Procambium: Procambium forms xylem, phloem and cambium of plants. It forms transport tissue or vascular bundles. In many plants it forms a cycle or pericycle.
12. Ground meristem: The ground meristem gives rise to the cortex, pith and medulla of the plant.

1. Cambium forms cork tissue.
2. It produces secondary xylem and secondary phloem.
3. It forms the secondary cortex.
4. Secondary medulla is formed from cambium.
5. Cambium has a role in the formation of complementary cells and lenticels.
6. Plants grow in length and width by the action of cambium.

Cambium is a type of dividing tissue. The cambium between xylem and phloem is called fascicular cambium. The cambium that forms between the vascular bundles is called interfascicular cambium. The secondary cambium that arises from the cortex is called cork cambium.

The dividing tissue that forms xylem, phloem and cambium of plants is called procambium. It is scattered in the stems of monocotyledonous plants and in ring form in the stems of dicotyledonous plants. It forms transport tissue or vascular bundles. In many plants it forms a cycle or pericycle.