The Growth Activity and Fertilizing Capacity of Submersely Cultivated Pollen Tubes of Nicotiana tabacum L.

Tobacco pollen was cultivated in shaken suspension cultures and the growth estimated by weighing the mass of germinated pollen separated from the nutrient solution. A formula for calculating mean pollen tube length from the weight of the culture has been derived for this pollen species. The growth of pollen tubes in vitro is shown to have a rhythmic character. The rapid growth comparable to the mean growth rate in styles is limited to short time intervals alternating with progressively extending periods of very depressed growth, which ceased entirely after 10-12h of cultivation. When tested by placental pollination in vitro, the fertilizing capacity of the pollen culture was found to increase during the first hour of cultivation but to decrease steadily thereafter. On the other hand, with the application of pollen tubes from culture on stigma, a short pre-cultivation period and even the mere wetting of pollen had a negative effect on the seed set. With pollen cultivated longer than 4h, no seed formation was observed

Use of Tissue Cultures in Plant Breeding

Since KANTA et al. (1) obtained viable seeds in vitro through pollination of ovules on excised placentae of Papaver somniferum, there has been a wide interest in applying this method for various plant species. This technique eliminating the stigma, style and tissues of ovary from the process of fertilization provides a means of overcoming self -incompatibility (2, 3) and its utilization in combating barriers to crossability has been proposed (4). A limited success has been achieved mainly in some genera of Papaveraceae, Solanaceae and Caryophyllaceae (e.g. 2, 3, 4, 5, 6), but most species tested failed to produce viable seeds in vitro (7)