No abstract

No abstract

Cross-compatible pollen tubes were cultured in detached flowers of apple (Malus domestica Borkh. cv. 'Cox's Orange Pippin'). Although the culture method was simple, the detached flowers proved to be adequate for our requirements, and after pollination they were incubated at 12 constant temperatures from 3·5° C to 33·5° C and sampled at intervals for microscopy. S-shaped growth curves (Gompertz function) were fitted to measurements of pollen-tube penetration within the styles, and each of the Gompertz parameters was expressed as a function of temperature. The model was defective at temperatures below 6° C, but a modification is described which improves this deficiency and yields a ten-parameter empirical model with temperature and incubation time as inputs, and pollen penetration as its output. An application of the model is described in which it provides a numerically integrated output of pollentube penetration from a series of temperature records. Potential uses for the model include predictions of pollen penetration for experimental use and testing for small differences in pollen-tube response to temperature, between cultivars, or between experimental treatments.

No abstract

Individual pollen grains may be assessed for viability and starch content by dusting a sample onto drops of an aqueous medium containing fluorescein diacetate and potassium iodide, and allowing them to accumulate free fluorescein for ten minutes. They are then illuminated with ultraviolet or blue light and photographed to record the proportion that fluoresce, as an index of viability. The preparation is exposed to iodine vapor and the same field of view rephotographed in bright field illumination to record starch content. Iodine vapor avoids disturbing the grains by adding further liquid, so that the same pollen grains may be classified by fluorescence and starch content. The method makes it possible to test whether viability and starch content are associated or depend on other variables, such as pollen-grain diameter. Iodine-potassium iodide is shown to be inadequate as a test for pollen viability. The method is quick and easy and provides data not otherwise available.