Dempsey, W. H.
Pollen viability and seed-setting ability have often been estimated by staining pollen grains or by germinating them in sucrose solutions or on agar. A test was made to see if the observation of pollen tubes in the style by means of fluoreiscence (Martin: TGC 9:38-39) would offer a more accurate means of pollen evaluation. Accordingly, pollen of unknown seed-setting ability which had been stored over CaCl\2, at 32 deg. F for various periods was applied to male-sterile Pearson (ms\2) and ms\17, a\1, c, d\1, l\1 (Rick) plants. Staining and germination tests of the pollen indicated all lots were 90-100% viable. Whole pistils or styles were collected two days after pollination, stained and squashed. In Vivo pollen tube observations on 2-5 styles indicated all pollen lots had germinated and penetrated to the ovules. The following table summarizes the results using stored pollen on male-sterile Pearson plants.
Pollen age Pollen tubes Pollin- Fruit Seed (months) Description in style ations set set Seedlings _______________________________________________________________ 38 Early Pak 0 - few 17 0 0 0 24 ? Few - many 17 0 0 0 17 Pearson Many 12 0 0 0 14 XL Very many 27 6 4 1 14 XL Many 13 3 3 3 14 Pearson Very many 7 5 0 0 4 Pearson Very many 11 9 100 52 _______________________________________________________________When stored pollen was used on male-sterile Stock 1 plants, similar results were obtained for fruit set, but no seed set was obtained except for the Pearson pollen stored for only 4 months. It is clear from these simple tests that the ability of pollen to germinate or of pollen tubes to grow either in vitro or in vivo cannot serve as a reliable index of their ability to fertilize ovules.