Effects of acidity and detergent on in vitro pollen germination and tube growth in forest tree species

The presence of 1 to 3 mg 1−1 sodium dodecylbenzensulfonate detergent, or a growth medium pH of 4.0–5.0, inhibited pollen germination and pollen tube elongation more in broad-leaved trees than in conifers. In the broad-leaved species, pollen germination and pollen tube elongation showed similar sensitivities to detergent and acidity, whereas in the conifers, pollen tube elongation was more sensitive than pollen germination to detergent and acidity. Although the germination percentage was low, conifer pollen germinated in the presence of detergent concentrations up to 15 mg l−1 and at acidities as low as pH 2.5 or 3.0. Pollen germination of most broad-leaved species was completely inhibited in the presence of detergent concentrations of more than 3–5 mg l−1; the only exceptions were some entomophilous species (e.g., Salix caprea L.) in which the ability of the pollen to germinate in high pollutant concentrations could be related to the presence of tryphyne.