An in vitro assay for assessing the effects of growth factors on Nicotiana alata pollen tubes

 A new method for assessing the effects of test compounds on Nicotiana alata pollen tubes in culture is described. Pollen tubes grow from a cluster of grains placed beneath a thin layer of gelled medium in which test substances are incorporated and from which evaporation is prevented by a covering layer of oil. Pollen tubes can grow to 8 mm in length in 24 h, which corresponds to about 25% of the maximum growth rate in styles. Growth is non-destructively measured. The developmental stages reached by cultured tubes are similar to those of tubes growing in styles; growth changes from being reserve-dependent to reserve-independent, callose plugs form, and the nucleus of the generative cell divides. Because culture volumes are small (10–20 μl per replicate), the effects of known concentrations of microgram quantities of compounds on the growth of pollen tubes can be tested. Received: 25 February 1997 / 21 July 1997