In Vitro and In Vivo Effects of Acidity and Trace Elements on Pollen Function

Abstract

Pollen development and activity are known to be among the more sensitive botanical indicators of atmospheric pollution (Feder 1981). Atmospheric pollution may directly effect the pollen by reducing its viability prior to pollination or by affecting the chemical environment of the stigmatic surface. Marked reductions in cone dimensions, seed weight and viability together with reduced pollen viability have been observed near to sources of air pollution (Antipov 1970). Furthermore, these effects may occur at pollution levels lower than that required for foliar injury (Houston and Dochinger 1977). Acidity of SO₂ fumigations under wet or high relative humidities was taken for granted by Dopp (1931), who suggested that the increased in vitro effect of SO₂ fumigation over the in vivo fumigation effect was due to extra buffering of the stigmatic surface. The acidification of the pollen media by SO2 fumigation was demonstrated by Karnosky and Stairs (1974). Murdy and Ragsdale (1980) working with Geranium carolinianum suggested that in vitro SO₂ effects on pollen may emulate in vivo effects under high relative humidity and the resultant reduced pollen germination and initial tube growth may reduce seed set. Such a reduction in in vivo pollen germination was related to reduced seed set in G. carolinianum by DuBay and Murdy (1983). Masaru et al. (1980), however, was to finally verify the importance of H⁺ ion inhibition of pollen function in vitro and suggest the implications of acidic precipitation which was confirmed in vivo by Cox (1984).