Experiments on Palynology | Botany

The below mentioned article includes a list of five experiments on palynology.

Aim of the Experiment: 1. To calculate the pollen viability by histo-chemical test in the laboratory.

Requirements:

A bisexual flower, water, slide, acetocarmine, cover slips, microscope, needle.

Method:

1. Separate an anther of a bisexual flower with the help of a needle and sprinkle some of its pollen grains in a drop of water on a slide.

2. Add a few drops of acetocarmine (2%) with a dropper and wait for 5 minutes.

3. Put a cover slip and observe under microscope.

4. Count the total number of pollen grains in the microscopic field and also those pollen grains which have taken red stain.

Observations and Results:

Viable pollen grains take red stain of acetocarmine whereas non-viable grains do not take the stain. Calculate the percent­age of viable pollen grains in the microscopic field. (It may, however, be noted that the staining test is not an absolutely reliable test for viability).

Aim of the Experiment: 2. To demonstrate the “hanging drop method” of pollen germination.

Requirements:

Mature flowers of any plant (e.g. Diantbus, Abelmoscbus or Rosa) containing sta­mens, sucrose, boric acid, magnesium sulphate, potassium nitrate, calcium nitrate, distilled water, beaker, microscope, measuring cylinder, dropper, slides and cover slips.

Preparation of Germination Medium:

Take some distilled water in a measuring cylinder and dis­solve in it 10 gm sucrose, 10 mg boric acid, 20 mg magnesium sulphate, 10 mg potassium nitrate and 30 mg calcium nitrate. Add some more distilled water to raise the level up to 100 ml in the measuring cylinder.

Method:

1. Hold a cover slip by its edges and put on it a very small drop of germinating medium (Fig. 7).

2. With the help of a soft brush spray the pollen grains from a mature anther on the germinating medium drop.

3. Take a cavity slide and put a little amount of grease around its cavity. Place the inverted cover- slip on the cavity in such a way so that the germinating medium drop does not touch its sur­face. Keep the cavity slide undisturbed for 20-30 minutes and then observe under microscope.

Observations and Results:

Germinating pollen grains with pollen tubes are observed. Pollen tube ruptures the exine and comes out.

Aim of the Experiment: 3. To study the pollen grains of some plants belonging to monocotyledons

Requirements:

Mature flowers of the above mentioned plants containing stamens; other requirements as per the particular method used for the pollen preparation.

Observations and Results:

1. Canna (Cannaceae):

Pollen grains (Fig. 8 A) are inaperturate; the ectine surface spinose and the two layers of very thin exine are almost undifferentiated. In some of the Canna varieties there is a gradual reduction of spinules, resulting their complete absence in some varieties; in some other varieties there is the radial division of the ectine into colurnellae.

2. Commelina collestris (Commelinaceae):

Pollen grains (Fig. 8 B) are 1-colpate and the aperture area shows considerable heterogeneity. The colpus is marked by an interrupted area of the exine forming irregular or regular insulae (exinous is­lands). It also lacks tegillum, leaving the granular or spinescent processes. Occurrence of insulae in the colpi region is the characteristic feature of Commelinaceae.

3. Crocus specious (Iridaceae):

The pollen grains (Fig. 8 C) are aperturate (porate); the apertures (colpi or pores) are weakly defined, become elon­gate and furrow-like and even joined from end to end to form a spiraperturate structure; sometimes they are inaperturate or pantoaperturate.

4. Cocos nucifera (Palmae):

Pollen gmins are usually 1-colpate (Fig. 8 D) but sometimes 2-4 colpate or trichotomocolpate or with a pore; the exine surface patterns are also variable, being smooth-walled or provided with depressions (reticulate or foveolate), or with excrescences (spi­nous, verrucate or pilate). Unique feature is the occurrence of monocolpate grains in combination with porate grains and trichotomocolpate grains. Inaperturate grains are absent.

5. Cyperus rotundus (Cyperaceae):

Grains are 4- aperturate with 3 zonal colpi and one pore at the broader end (Fig. 8 E); ellipsoidal; longest axis 30.08 µ (range 27.2-33.6 µ), shortest axis 22.08 µ (range 17.6-25.6 µ); colpus tenuimarginate; exine thickness 1.2 µ; ectine thicker than endine; surface granulose.

Aim of the Experiment: 4. To study the pollen grains of some plants belonging to dicotyledons.

Requirements:

Mature flowers of the above mentioned plants containing stamens; other re­quirements as per the particular method used for pollen preparation.

Observations and Results:

1. Baubinia (Caesalpinieae):

Pollen grains and B), Crocus specious (C), Cocos nucifera (D) and Cyperus aperture forms are highly variable; apertures well defined, 3-zonocolpate, ectine striate, endocolpium lolongate and size is 14 × 9µ (Bauhinia krugii, Fig. 9 A); ectine verucate (B retusa, Fig. 9B); endocolpium circular (B. vabli, Fig. 9C); aper­ture faintly defined and 3-zonoporate in B. malabarica (Fig. 9D).

2. Caesalpiniapulcherrima (Caesalpinieae):

Pollen grains (Fig. 10 A, B) are spheroidal in shape and range between 77-99µ in size; 3-zonoaperturate; pseudocolpi ends meet at the poles to form synpseudocolpate condition; exine 4 to 6µ in thickness; synpseudocolpi are broad; ectine surface exhibits a gradation of patterns from areolate, rugulate and reticulate ornamentations; in the region of pseudocolpium the ectine shows pilate pattern.

3. Althaea rosea (Malvaceae):

Pollen grains (Fig. 10 C) are pantoporate, spheroidal, ranging 125- 140µ in diameter; pores circular with an average diameter of about 2µ; distance between pores is approximately 6-8µ; exine spinose, about 7µ thick; ectine is thinner than endine; spines are dimorphic, i.e., short (5-6µ) as well as long (18-21µ) in height.

4. Hibiscus (Malvaceae):

Pollen grains pantoporate, thick-walled and show several variations among different species and even within the varieties; grains are spinose (Fig. 9E) and the excrescence system varies from baculate, verrucate, clavate and even with divided ends; spines on ectine are short (below 30µ).

5. Carica papaya (Caricaceae):

Pollen grains (Fig. 10 D) are 3-zonocolporate, subprolate or rarely spheroidal; ectocolpium somewhat constricted in the middle; endocolpium lalongate with somewhat round lateral end; exine about 2µ in thickness; thickness of ectine and endine is more or less the same; ectine faintly reticulate.

6. Brassica campestris (Brassicaceae):

Pollen grains represent typical dicot grains and contain 3 zonal furrows or colpi (Fig. 11A); the colpi are well demarcated; the exine Surface is simple, either smooth, reticulate or granulate.

7. Bougainvillaea (Nyctaginaceae):

Pollen grains (Fig. 11B) are 3-colpate; ectine is reticulate and in the reticulum of some grains occur large brochi while in others occur smaller brochi.

8. Morus Alba (Moraceae):

The pollen grains (Fig. 11C) are porate and pororate; the pores are 2 and often provided with thickened margins; the exine is simple, being granulate or foveolate.

Aim of the Experiment: 5. To determine the shape of the pollen grains.

Method:

In equatorial view, the shape of the radio-symmetric grains is expressed from the figure obtained by the ratio of polar diameter (P) and equatorial diameter (E) multiplied by 100, i.e. by the formula P × 100/E

If the value of P×100/E is less than 50, the shape of the pollen grain is peroblate.

If it is between 50 and 75, the shape of the grain is oblate.

If it is between 76 and 88, the shape of the grain is said to be suboblate.

If it is between 89 and 100, the shape of the grain is oblate spheroidal.

If it is between 101 and 114, the shape of the grain is prolate spheroidal.

If it is between 115 and 133, the shape of the grain is subprolate.

If it is between 134 and 200, the shape of the grain is prolate.

If it is over 200, the shape of the grain is perprolate.