SXConline
Cytology
Hydrilla

Objectives:

1. To develop an understanding about the arrangement of cells.

            2. To study about the shape and size of different types of cells.

3. To study the internal organisation of different types of cells.

Requirements:

            1. Apparatus: Watch glass, slides, cover slips, forceps, scissors, brush,

                                    needle, beaker, blotting paper etc

            2. Material: Hydrilla leaf

            3. Chemicals: Saffranin, Glycerine

Procedure:

A young leaf of Hydrilla was plucked and dipped in saffranin solution in a watch glass for few seconds. It was washed with water and placed over a drop of glycerine on a slide. It was then covered with coverslip. the slide was observed under microscope.

A temporary slide of the same material was prepared again but without staining it with saffranine and observed under microscope.

 

Observations:

The following observations were made under 10x and 40x:

  1. The cells were  compactly arranged in rows without intercellular spaces like bricks on a wall.
  2. The cells were of variable sizes.
  3. The cells were more or less rectangular or brick shaped.
  4. Each cell was surrounded by a cell wall.
  5. In between the cell walls of two cells, a cementing layer called middle lamella was seen.
  6. Each cell was filled with granular cytoplasm which enclosed a nucleus and numerous round and green structures called chloroplasts.
  7. A large central vacuole was surrounded by peripheral cytoplasm.
  8. The outer boundary of cytoplasm which is tightly attached with cell wall is called cell membrane.

 

Conclusions:

All the cells that had been observed had some similarities as well as dissimilarities:

  1. All  the cells were compactly arranged without any intercellular spaces.
  2. All the cells were eukaryotic and contained peripheral granulated cytoplasm. Because of the presence of small or large vacuole the nucleus was pushed towards the periphery. Each cell was surrounded by a cell wall and middle lamella was present between the cell walls of two adjoining cells.
  3. Variations were observed in shape and size of cells. Some cells were rectangular, some hexagonal, some bean-shaped and irregular.
  4. Chloroplasts were present in some green walls.
  5. In some cases, guard cells and stomata were also seen.

 

Thus, all the cells that were observed were plant cells as they were bound by rigid cell wall, and contained central vacuole.

View the Figure for this Practical