The sensitivity of pollen from various coniferous and broad–leaved trees to combinations of acidity and trace metals

Abstract

The effects of acidic and trace element components of polluted rain on pollen germination and tube growth in vitro are described. The sensitivity of pollen to pH in vitro was related to the species' position in canopy and was different for conifers and broad‐leaved trees. Most pollen assayed revealed significant inhibition of germination and germ tube growth in response to pHs currently observed in rain samples in eastern Canada. Acer saccharum Marsh and Betula alleghaniensis Britt. pollen in vitro showed a high sensitivity to pH in combination with copper. The pollen of Populus tremuloides L, was shown to be highly sensitive to pH, and a synergism between pH and copper on pollen function in this species was also demonstrated. This was in contrast to the general antagonistic interaction of pH and copper noted in the other species tested in which copper by it self either did not affect pollen function or was stimulatory. Zinc has little or no effect, whereas lead at the concentrations used significantly inhibited both germination of Pinus strobus L. pollen at pH 5.6–3.6 and tube growth of both P. strobus and Pinus resinosa Ait. The increase in pollen mortality in response to air pollution at the time of pollination raises certain implications for reproduction and breeding. These implications are also discussed in the light of the significant genetic overlap between pollen and sporophytes of higher plants. Copyright © 1988, Wiley Blackwell. All rights reserved