MICROSCOPIC STUDY AND IDENTIFICATION OF TISSUES PERTINENT TO STEM, ROOT LEAF, SEED, FRUIT AND FLOWER
Aim:
To study the microscopic features of tissues pertinent to root, stem, leaf, seed, fruit and flower.
Requirements:
Fresh or museum specimens, model of specimens, Photographs or pictures of specimens of roots, stem, leaf, seeds, fruit, flower, a sharp blade, microscope, slides, coverslips, watch glass, safranin (1gm in 100 ml of 50% ethanol), glycerin, brush, blotting paper.
Observation:
- Monocot stem:
Observations:
1. Epidermis: It is the outermost covering of the stem represented by a single layer of compactly arranged, barrel-shaped parenchyma cells. The epidermis is covered by a thin layer of cuticle and with stomata bounded by dumbbell-shaped guard cells. Trichomes are absent.
2. Hypodermis: It lies immediately below the epidermis. It is represented by a few layers of compactly arranged sclerenchyma cells.
3. Ground tissue: The ground tissue is represented by several layers of loosely arranged parenchyma cells enclosing prominent intercellular spaces. It is the main central part of the stem.
4. Vascular Bundle: They are found irregularly scattered in the ground tissue. Each bundle is conjoint, collateral and closed. Towards the periphery, the bundles are smaller in size while towards the centre, they are larger in size. The smaller bundles are younger, while the larger ones are older. Hence, the arrangement is described as centrifugal. Each vascular bundle has a covering called a bundle sheath formed by a single layer of sclerenchyma cells. In the xylem, there are two metaxylem and two protoxylem vessels arranged in the shape of ‘Y. In the phloem, only sieve tubes, companion cells and phloem fibres are present. Phloem parenchyma is absent.
- Dicot stem:
1. Epidermis: It is the outermost layer of (dicot) stem with multicellular epidermal stem hair. The cells are living, barrel-shaped and compactly arranged without intercellular spaces and chloroplasts.
2 Hypodermis: It consists of 2-3 layers of collenchymatous cells. The cells are thick at the corners.
3. Cortex It is the major part of the stem represented by several layers of loosely arranged parenchyma cells.
4. Endodermis: It is the innermost layer of the cortex. It consists of barrel-shaped cells.
5. Pericycle: It is multilayered and present in the form of parenchymatous and sclerenchymatous patches (outside the vascular bundles only).
6. Vascular bundles: Inside the pericycle, there is a ring of vascular bundles. 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 (protoxylem towards the centre).
7. Pith It is the innermost part of the stem formed by a group of loosely arranged parenchyma cells. Intercellular spaces are prominent. Pith helps the storage of food.
- Monocot root
1. Epidermis (Epiblema or Piliferous layer): It is single-layered, thin-walled, colourless, polygonal without intercellular spaces, with the presence of unicellular root hair.
2. Cortex: It lies inner to the epidermis. It is a multilayered cortex that consists of compactly arranged cells
3. Endodermis: It is single-layered that lied inner to the cortex. It consists of barrel-shaped parenchyma without intercellular spaces. Casparian strips are little present but passage cells are absent.
4. Stele: It is the central cylinder of the root consisting of pericycle, conjunctive tissue, pith and vascular bundles.
5. Pericycle: It is the outermost covering of the stele represented by a single layer of parenchyma cells.
6. Vascular Bundles: Radial types of vascular bundles are present, i.e., xylem and phloem alternate with each other and are arranged in the form of a ring. There are eight bundles each of xylem and phloem. Hence, the condition is described as polyarch. Xylem is described as exarch (protoxylem towards periphery).
7. Pith: It is formed by a large number of parenchymatous cells. Pith lies in the centre of the root.
- Dicot root:
1. Epidermis: It is the outermost uni-layered with several unicellular root hairs. It consists of thin-walled, compactly arranged living parenchymatous cells. A cuticle and stomata are absent.
2. Cortex: It lies inner to the epidermis. It is represented by several layers of loosely arranged parenchyma cells Intercellular spaces are prominent. The cortex is mainly meant for the storage of water
3 Endodermis: Cortex is limited on the inner side by single-layered endodermis. The endodermal cells consist of casparian strips.
4. Pericycle: It is the outermost layer of the stele and is composed of a uniseriate layer of parenchymatous cells without intercellular spaces.
5. Vascular Bundles: Radial types of vascular bundles are present. The xylem and phloem bundles alternate with each other. The number of xylem bundles ranges from 2-5. When the four bundles are present, it is known as tetrarch. Xylem vessels are polygonal. Protoxylem vessels are present towards the pericycle and metaxylem vessels are present towards the centre of the root. Such an arrangement is called an exarch.
6. Pith: It is feebly developed and centrally located. It consists of thin-walled polygonal parenchyma cells with intercellular spaces.
- Leaf:
Procedure: Remove the peel of a leaf taken from a potted plant and place it on a slide containing a drop of water or glycerine. Observe it under the microscope. Now take the peel from the other surface and repeat the procedure. Compare the upper and the lower surface.
Observations: Polygonal cells of the epidermis are seen under the microscope stomata with kidney-shaped guard cells are also seen here and there. Count the total number of epidermal cells as well as the total number of stomata visible in one field. Take 3-4 readings at different places and calculate the average stomatal index by using the following formula:
Stomatal Index (%) = Total number of stomata x 100
Total no. of epidermal cells + Total no. of stomata
- Plant tissues (Palisade parenchyma, collenchyma, sclerenchyma, xylem and pholem):
Theory: The organs of plants consist of different tissues. The study of tissues is called histology. A tissue is a group of cells that are similar in origin, structure and function.
Mainly tissues are of two types: a. Meristematic tissue and b. Permanent tissues.
Meristematic tissues are present at the growing points of the plant and are responsible for the growth of plants. Permanent tissues are made up of mature cells that have acquired permanent shape and cannot divide.
Permanent tissues are also of two types (i) Simple permanent tissue and complex permanent tissues. Simple permanent tissues consist of only one type of cell. Whereas complex permanent tissue is made up of more than one type of cell. Parenchyma, collenchymas and sclerenchyma are examples of simple permanent tissues. Xylem and phloem are examples of complex permanent tissues.
1. Parenchyma
Cells are spherical or oval and isodiametric.
There are intercellular spaces between the cells.
Cells contain a prominent nucleus and reserve food material.
Each cell has a large central vacuole.
These cells are living and are thin-walled.
2. Collenchyma
Tissues are made up of isodiametric cells.
Their cell wall is thick more so in the corners of the cell.
There are no intercellular spaces.
The cells contain protoplast and are living.
It provides strength and flexibility to the young stem.
3. Sclerenchyma:
The cells are long and highly thick-walled due to the deposition of lignin.
Protoplasm is crushed and cells become dead at maturity.
The ends of the cells taper into sharp points.
The cell cavity is very small.
4. Xylem:
It is a complex tissue.
It is made up of four kinds of elements, a Tracheids, b. Vessels, c. Xylem parenchyma and d. Xylem fibres.
a.Tracheids
Tracheids present are much elongated, highly thick-walled with large cavities.
Cells are devoid of protoplast and hence they are dead cells.
Tracheids have lumen without any content in them.
Depending upon the type of thickness tracheids are classified into annular reticulate, scalariform and pitted.
b.Vessels
These are long tube-like bodies that conduct water and minerals.
These vessels are formed from a row of cylindrical cells arranged in longitudinal series.
These also have five types of lignifications.
c.Xylem parenchyma:
These are thin-walled living cells.
These cells store starch and fatty substances.
These are abundant in the secondary xylem of many plants.
d.Xylem fibres:
These fibres provide mechanical strength to the plant.
These fibres are highly lignified sclerenchyma fibres.
These are dead cells.
5. Phloem
These compound tissues are formed of four types of cells:
a. Sieve tube cells b. Companion cells c. Phloem parenchyma and d. Phloem fibres
a. Sieve tube cells.
These cells are multicellular, elongated and tube-like cells.
Their transverse walls are porous and oblique.
Some tubes have thin walls and are enucleated at maturity.
Sieve tube cells have sieve plates at the end walls.
b. Companion cells:
These are living cells that are associated with sieve tubes.
These companion cells are firmly attached to the sieve tube.
These have dense cytoplasm and prominent nuclei.
These occur on the lateral walls of sieve tubes.
c. Phloem parenchyma:
These are formed of thin and living parenchymal cells.
These are connected with the storage of organic food materials.
d. Phloem fibres:
These are dead and lignified sclerenchyma fibres that provide mechanical strength to the plant.
The lignified walls have single pits.
Remedial Biology Practicals
- Introduction to experiments in biology a) Study of Microscope b) Section cutting techniques c) Mounting and staining d) Permanent slide preparation 2. Study of cell and its inclusions 3. Study of Stem, Root, Leaf, seed, fruit, flower and their modifications 4. Detailed study of frog by using computer models 5. Microscopic study and identification of tissues pertinent to Stem, Root Leaf, seed, fruit and flower 6. Identification of bones 7. Determination of blood group 8. Determination of blood pressure 9. Determination of tidal volume
First Year B Pharm Notes, Syllabus, Books, PDF Subjectwise/Topicwise
First Year B Pharm Notes, Syllabus, Books, PDF Subjectwise/Topicwise
