Preparation of slide for study of internal structure of stem, root and leaves of dicot and monocot plant.

 Aim of Experiment: Preparation of slide for study of internal structure of stem, root and leaves of dicot and monocot plant.

Principle: The study of internal morphology, i.e., cells of various tissues in an organ of a living body is called Anatomy. Tissue, which is a group of cells performing a common function, may be simple (parenchyma, collenchyma and sclerenchyma) or complex containing more than one type of cells (xylem and phloem). The tissues may be temporary (meristematic) or permanent (sclerenchyma, parenchyma and collenchyma).

The internal organisation of these tissues differs in root, stem and leaves. These differences are given in tabular form for easy identification. Various tissues which constitute roots and stems are described briefly.

Material Required : Preserved material of sunflower root and stem, maize root and stem, microscope, sharp blade, slides, watch glass, coverslips, safranin (1gm in 100ml of 50% ethanol), brush, glycerine, blotting paper

Procedure :

Sections Preparation

·        Collect a few thin young part of plants (i.e., non-woody/herbaceous without any secondary growth).

·        Use potato piece/Calotropis stem pith for embedding the material to be sectioned. If material is thick, it can be directly sectioned without embedding them in pith.

·        Hold the material between the thumb and index finger in such a way that the tips of the finger and smooth cut surface of the material are in a line, while the tip of the thumb is just a few mm below the upper surface of the material.

·        Wet the surfaces of razor blade/scalpel blade.

·        Carefully move the blade horizontally over the surface of material in quick succession in a manner that a very thin and complete slice of the material is cut and obtained over the surface of razor blade.

·        After cutting several sections in this manner, transfer all these into a watch glass containing water.

Staining of Plant Material: Make a visual observation of the sections cut and pick the thinnest possible and complete sections and transfer it into a watch glass containing safranin and allow these to remain there for about 2 minutes.
With the help of a brush gently transfer the section into another watch glass containing water to remove excess of safranin stain.

Mounting: On a clean slide, place a stained section in the middle of the slide in mounting medium
containing one drop of glycerine usually. Using a needle, slowly places the coverslip.
An excess of water or glycerine from the edge of the coverslip can be removed by placing
blotting paper.

Precautions:

·        While working with sections, use a brush.

·        Gently place the coverslip in order to avoid air bubbles.

·        Excess glycerine can be removed with filter paper.

·        Root parts should be stained before sectioning.

 

Study pollen germination on a slide

 

Aim of Experiment: Study pollen germination on a slide.

Specimen Required: Fresh seasonal flower

Apparatus Required: Slide, Needles, coverslips, microscope, beaker, dropper

Chemicals Required: Sucrose, boric acid, magnesium sulphate, Potassium nitrate.

Procedure:

1. Prepare a nutrient solution by dissolving 10g of sucrose, 10g boric acid, 30mg magnesium sulphate and 20mg Potassium nitrate in 100ml of water.

2. Take a few drops of this solution on a clean slide, and dust a few pollen grains from the stamen of a mature flower on it.

3. Observe the slide on the microscope after 5 minutes and then observe it regularly for about half an hour

Observations: 

(1) Observe   many   pollen    grains   germinating   over   stigma.  The growth of the pollen tube   is stimulated   by sugary substances secreted by the stigma.

(2) Pollen tube carrying with it tube nucleus and the generative nucleus. 

(3)  The   generative   nucleus divides forming two male gametes.

(4) Count the number of germinated pollen grains.

 

Precautions:

There are precautions to be observed while performing this experiment:

1. Dirty or previously used slides should not be used for dusting pollen grains. Slides should be clean and dry for use.
2. Only a few drops of the nutrient medium is required for germination. 2-3 drops of the solution are enough, more than that may hinder the process of pollen germination.
3. Only freshly plucked flowers should be used and the experiment should be conducted within sometime of plucking.
4. The cavity slide used for observation should have depression at the center so that the solution can be held in that cavity and does not flow.

  

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