Pollen Germination and Pollen-Tube Characteristics in a Range of Apple Cultivars

Pollen-tube growth characteristics are being used increasingly to investigate compatibility relationships in plants. A study was initiated to define more fully the characteristics of compatible and incompatible pollen-tube growth in 40 apple cultivars. Individual reactions varied in detail, but, in general, diploid pollen averaged over 70% germination, triploid pollen less than 10%. Compatible pollen tubes grew rapidly down the style and were characterized by small widely spaced, intermittent callose plugs and the absence of terminal plugs. Incompatible tubes were slower growing, often stopping completely, and had heavy depositions of callose tissue along and at the end of the tube.