Aerobiologia 17: 261–267, 2001. © 2001 Kluwer Academic Publishers. Printed in the Netherlands. 261 Aerobiology, biodiversity and chemistry of plant trichomes in the tropics at Bodh Gaya, India – a biopollutant and the suspected human allergen Anupam Sinha 1 , Krishn Bihari Mishra 1,2 & Raju Kumar 1,3 1 Ecology Research Laboratory, Department of Botany, Jamshedpur Co-operative College, Jamshedpur – 831001, India; 2 present address: University Department of Botany, Magadh University, Bodh Gaya, India; 3 present address: Usha Martin Industries Ltd., P.O. Box No.: 147 Jamshedpur, India Received 8 June 1999; accepted in final form 18 April 2001 Key words: allergen, carbohydrate, diversity, protein, trichomes Abstract Aerobiology, diversity and chemistry of some air borne plant trichomes were studied at Magadh University campus, Bodh Gaya, India between September 1995 and August 1996. Thirty-three morphotypes of trichomes were tapped using a Gravity Air sampler. The different types of trichomes showed pronounced seasonality in their distribution pattern. The simple non-septate trichomes of grasses were predominant throughout the year. The other commonly observed trichomes were comparable to that of Chrysanthemum, Tridax, Solanum, Amaranthus and Martynia. Trichomes. The Shannon diversity index of trichomes fluctuated widely (1.063–2.867) during different months of the year. This suggests that seasonality had definite bearing on the composition of aerobiota. Relative humidity was found to play greater role in the case of a number of morphotypes (67%), diversity index (50%) and species richness (61%) but in the case of index of dominance (62%), rainfall played a greater role at P < 0.01 level. The trichomes of a few selected plant species, the pollen grains of which are reported allergens, were chemically analysed by collecting them in bulk. They were found to be fairly rich in their total protein (9.58 to 93.60 mg/g) and carbohydrate (10.0 to 20.20 mg/g) contents. 1. Introduction Trichomes are minute epidermal outgrowth of plants, which are constantly present in the air (Sinha and Mishra, 1994) along with fungal spores and pollen- grains. It is suspected that the trichomes of plant pollens which are reported allergens may cause allergy in Human beings. This may be due to the pres- ence of some specific chemicals contained in the parent plants. Positive results have been observed by Sahay (1998) in the case of grass trichomes. However, extensive aerobiological, biodiversity, biochemical and clinical investigations of trichomes is required before their allergenic nature can be established with certainty. Metcalfe (1963) and Metcalfe and Chalk (1965) observed wide morphological variation in the trichomes of ground flora. Ramayya (1972) studied the classification and phylogeny of trichomes of angiosperms. Lavania (1990) recorded the morpho- logical variations of trichomes of Solanum in India. Extensive aerobiological investigations of air trich- omes were conducted by Sinha (1986), Sinha and Mishra (1994) and Mishra and Sinha (1988) with a view to exploring the incidence of some aller- genic trichomes in the ambient air of Bodh Gaya. Chopra (1958) chemically analysed the stinging hairs of Urtica dioca and reported the presence of acetyl choline, histamine and 5-hydroxy-tryptamine (5-HT) which cause irritation and symptoms of urticaria. Kanchan and Jayachandra (1980) identified the pres- ence of chemical inhibitors like parthenine, caffeic acid, vanillic acid and fumaric acid from the trichome leachates of Parthenium hysterophorus. During the study of ultrastructure, development and secretion of Inula viscosa hairs, Warker and Fahn (1981) reported that head cells of the trichomes secrete lipids, poly-