POLLEN GERMINATION, TUBE GROWTH AND MORPHOLOGY, AND MICROTUBULE ORGANIZATION AFTER EXPOSURE TO BENOMYL

The inhibitory effects of benomyl on pollen tube growth have received little attention, particularly at the microscopic and immunohistochemi cal levels. Pollen germination and tube growth in the presence of beno myl were evaluated in Tradescantia virginiana to investigate the effec ts of this fungicide on pollen germination rate, tube growth and morph ology, and microtubule (Mt) organization. Benomyl was incorporated in germination media at 0, 480, 600 or 720 mg l(-1). Inhibition of pollen germination, cytoplasmic streaming, and tube elongation were associat ed with benomyl treatments. Benomyl also induced abnormal pollen tube morphology and Mt organization. Compared to controls, Mts in the treat ed tubes were characteristically fewer in number, fragmented, sinuous and increasingly disorganized. At the two highest benomyl concentratio ns, Mts were considerably fewer or absent in apical/subapical regions of the pollen tubes. This work verifies that benomyl incorporated into germination media at concentrations lower than recommended field rate s inhibit pollen germination and tube growth, and that the effects are associated with alterations of Mt organization.