Effects of anoxia on pollen tube growth and tube wall formation of Impatiens glandulifera

Summary

When pollen of Impatiens glandulifera was cultured in aerated liquid medium for 1 h, 70% of the pollen grains germinated; these attained an average tube length of 1 mm. Subsequently, these aerobic growth conditions were changed to anaerobic by substituting a nitrogen inlet for the air inlet. As a result, the pollen tubes stopped elongating and burst. The ultrastructural changes which occurred upon inducing anoxia were studied with samples taken at 0 s, 45 s, and 4 min after changing the gas. Anoxia caused rapid and considerable changes in the ultrastructure of the dictyosome vesicles involved in cell wall formation. There was an increase in the osmiophyly of the vesicle content, and the presence of fibrillar material became apparent. Simultaneously, the fusion behavior of the dictyosome vesicles changed. Instead of the normal fusion of the dictyosome vesicles with the plasma membrane, there was a premature fusion of the vesicles with each other inside the cytoplasm that resulted in the formation of aggregates. Furthermore, the cell wall precursors that were excreted were not incorporated in their usual configuration into the growing cell wall. Instead of a smooth inner cell wall surface, irregular thickenings were formed.