Pollen Production

Several workers on pollen have made an attempt to assess the quantum of pollen discharge to the atmosphere (Agnihotri and Singh 1975; Khandelwal and Mittre 1973; Nair and Rastogi 1963; Mondal and Mandal 1998, Kessler & Harley 2004).

The quantity of pollen in the air depends on several factors, the most important being pollen production in the individual species. The amount of pollen production and methods of dispersal are very important factors, which are directly or indirectly involved in causing environmental pollution and allergy.

Nair and Rastogi (1963) had suggested a method of assessing pollen production within an anther of a flower. Unopened but mature flower buds are usually collected in the morning hours (6:30 to 8:30 am) Pollen grains were extracted from the anther by crushing and dispersing in 50 drops of 50% glycerine. One drop of this mixture of pollen in glycerine was placed on a microscope slide and covered with square cover glass of 18 x 18 mm dimension. The slide thus prepared was examined under the microscope and the pollen grains were counted. This was repeated by counting pollen grains in 10 drops of pollen dispersion. An average number of pollen was determined and multiplied by 50 to obtain the pollen production per anther.

In case of polyads, on account of their large size the anther was crushed and contents dispersed uniformly in 5 drops of 50% glycerine. Five drops of the mixture was placed on a slide covered with cover glass. The pollen count was determined for 20 anthers from different flowers and an average was taken to determine pollen production. Pollen production is usually studied in the flower buds. If the pollen grains are large, the Haemocytometer method (Oberle and Goertzen 1952; Nagarajan et al., 1972) for estimating pollen count is not suitable. In such a case, counting of pollen grains is done by other methods.

In as early as 1940, Erdtman had suggested the simplest method of determination of pollen productivity. According to him anthers of a mature bud are crushed in 1.5 ml of 50% glycerine comprising 30 drops. Pollen grains are counted in five drops for each sample and an average is taken in one drop. This number is multiplied by 30 so as to get the total number of pollen grains per flower.

In general the pollen production is controlled not only by their size, but also by genetic and physiological factors. Average pollen production per flower in Acacia mangium is reported to be the highest (16,640), followed by Acacia auriculiformis (15,360), Mimosa invisa var. invisa (12,800), Albizzia falcataria (12,288). Out of these four plants, three are tree species, which are capable of contributing an enormous quantity of pollen to the atmosphere. The pollen of these three tree species have been proved to cause pollen allergy in human beings.

Agashe and Soucenadin (1992) had worked out pollen productivity in certain allergenically significant plants in Bangalore, India. Pollen productivity is listed in the following table.

Table 13.1 Duration of flowering and pollen production of allergenically significant pollen in the atmosphere of Bangalore.

Name of the plant

Duration of flowering

Pollen grains/anther

Casuarina equisetifolia*

Jan-Mar, Sep-Oct

787

Eucalyptus

Jan-Dec

274G

Ricinus communis*

Jan-Dec

491

Amaranthus spinosus*

Jan-Dec

57G9

Holoptelea integrifolia**

Jan-Mar

183G

Plant species * Abundant ** Rare

Plant species * Abundant ** Rare

Correlation between the size of the individual pollen grains and pollen production, that is the number of pollen produced per anther

Samanea saman has 32 grains in the polyad where the polyad size (85.15 ^m) is roughly double that of the Acacia species (average size of

40.83 ^m) and the pollen count in Samanea saman is 256 which is double that of Acacia species with the pollen count of 128. The size of the individual pollen in the polyad of Acacia species varies from 8-11 ^m, where as the individual pollen size in Samanea saman varies from 20-30 ^m, these results are in conformity with the view that there is a positive correlation between pollen size and pollen production per anther.

The pollen output or the pollen production is expressed in different ways. Different authors express the pollen production either as the absolute number of pollen grains per anther, flower, inflorescence shoot or the entire plant. However, majority of the palynologists prefer to interpret the pollen production in terms of number of pollen grains produced per anther.

A single anther of Betula is known to contain about 10,000 pollen grains, while a single catkin of Betula produces more than 5 million pollen grains. A shoot with inflorosence of Cannabis sativa (Hemp) may produce more than 500 million pollen grains. Conifers are also known to be high pollen producers. A 10-year-old branch system bearing male cones in Pinus sylvestris may produce about 350 million pollen grains. When the mass of pollen grains are dispersed from microsporangia of male cones of Pinus, a cream or light brown coloured cloud containing pollen is observed.

Some fungi are known to exceed angiosperms in the production of spores. In Lycoperdon giaganteum (giant puff ball) the estimated total number of spores produced amounted to about trillions (Buller 1909). The pollen production is also sometimes expressed in relative terms rather than absolutely. Hasselman (1919) estimated an annual production of about 75,000 tonnes of pollen of Picea (Spruce) in southern and central Sweden. A quantity of 28 to 60 kg of Picea pollen per hectare was reported.

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Responses

  • Ezio
    What is the quantity of pollen produced in the anther?
    2 years ago
  • Beato
    What is pollen production?
    2 years ago

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