Needle wax surface structure of Pinus sylvestris as affected by ammonia

Wax surfaces of current, first and second year needles of Pinus sylvestris L. from Open Top Chambers, both fumigated with ammonia and unfumigated, were examined with the scanning electron microscope. In the course of time the wax rodlets on peristomatal rims of treated and untreated plants became fused and agglomerated to various extents into morphologically different types of crusts. Compact peristomatal crusts were most frequent. Porous, particulate and ‘melted’ peristomatal crusts as well as epistomatal crusts were of rare occurrence and presumably represented a random phenomenon. No correlation was found between appearance of wax crusts and ammonia fumigation. Ammonia treatment did not affect fungal growth either. Quantitative estimates indicated a very weak, statistically insignificant, tendency of ammonia to increase the rate of the normal, age dependent wax degradation. Observations on young needles developing after prolonged fumigation are suggestive of an indirect effect of ammonia on the rate of crystalline wax degradation.