Category: Biology Second Paper

When multiple tissues perform similar functions collectively, it is called a tissue system. Scientist Sachs (1875) divided plant tissues into three parts. Epidermal tissue system, ground tissue system and vascular tissue system.

1. Chlorenchyma produces food in the process of photosynthesis.
2. Permanent tissue transports water and food to different cells.
3. It is involved in secretion and excretion of various substances.
4. It protects the various organs of the plant.
5. It gives strength to the plant.

A permanent tissue that secretes various types of fluids is called a secretory tissue. Secretory tissues secrete enzymes, resins, resins, volatile oils, glues, etc. It is of two types. Thyroid tissue and glandular tissue.

(i) Phloem transports food in the plant body.
(ii) Stores food in the plant body.
(iii) Assists in photosynthesis of plants.
(iv) It imparts vigor to plants.
(v) Provides mechanical energy to plants.
(vi) It forms fibers in the plant body.

Greek word Phloos mean bark. It transports food from plant leaves to different parts of the body. It consists of four components. Synovial, companion cells, phloem parenchyma and phloem fibers. The resulting sivnol or sivcell does not have a nucleus. The fibers present in the secondary phloem are called bast fibers. Jute fibers are bast fibers.

(i) Transports water and mineral salts in the plant body.
(ii) Stores water and mineral salts in the plant body.
(iii) It imparts vigor to plants.
(iv) Provides mechanical energy to plants.
(v) Assists in photosynthesis of plants.
(vi) Helps plants in respiration.
(vii) Aids diffusion and osmosis in the plant body.
(viii) It forms wood in the plant body.
(ix) It participates in the formation of the main structure of the plant body.

When protoxylem is in the center and metaxylem is located around it, it is called centrach. Centarch xylem is found in fern plants.

When protoxylem and metaxylem are arranged on both sides, it is called mesarc. Mesarc xylem is found in the leaves of ferns and cycads.

If protoxylem is towards the center and metaxylem towards the periphery, it is called endarc. The xylem of stem is endarc in nature.

If protoxylem is towards the periphery and metaxylem towards the centre, it is called exarc. Root xylem is exarc in nature.