Photometric quantification of in vitro pollen tube growth: A new method suited to determine the cytotoxicity of various environmental substances

Abstract

The germination or tube wall elongation rate of pollen has frequently been used as an indicator for air pollutants and pesticides. A relatively simple method for the determination of pollutant toxicity is described and combinens both characteristics of pollen viability by calculating the amount of tube wall material produced within a defined period. The tubes of tobacco pollen were germinated in a culture medium containing the pollutants to be tested, were broken by sonication, purified and suspended in water. The optical density of this wall suspension read at 500 nm was related to the amount of tube wall material which was produced within a defined period. By plotting the optical density values against the concentrations of the pollutants, sigmoid dose-response curves were obtained from which ED 50 values could be calculated. ED 50 (50% effective dose) was defined to be the concentration of a toxic substance which causes a decrease of tube wall production to 50% of the total amount. Three toxic substances, 2,6-dichlorbenzonitrile, formaldehyde and ethanol, were used to test the method. The results revealed good reproducibility and high sensitivity of the toxicity test. The test works faster than methods based on microscopic calculation of pollen germination or pollen tube growth, and can be applied to a wide range of environmental substances, including herbicides and organic or inorganic air and water pollutants.