Abstract
The application of silver nitrate is a common option to induce staminate flowers in gynoecious cucumbers in order to maintain their progenies. The present study examined the effect of silver nitrate on the number of staminate flowers, and the performance of seeds produced by the induced staminate flowers. Six concentrations of silver nitrate at 0, 100, 200, 300, 400 and 500 ppm were applied to a gynoecious cucumber ‘ChibiTaro’. The number of staminate flowers increased at higher concentrations between 200 and 500 ppm, while there were no staminate flowers at 0 and 100 ppm. The staminate flowers induced at different concentrations were then pollinated separately on pistillate flowers of another gynoecious cultivar ‘Rensei’. The number of seeds per fruit after 500 ppm treatment was significantly higher than those after 200 and 400 ppm, although there was no consistent relationship between the number of seeds per fruit and silver nitrate concentration. The hundred seed weight showed a smaller value after 500 ppm treatment compared to those after 300 and 400 ppm but germination percentages of seeds were not significantly different among the concentrations either at harvest time or after eight years of storage. Microscopic examination of acetocarmine stained pollen of induced staminate flowers confirmed the absence of significant differences in pollen viability among the silver nitrate concentrations. Silver nitrate is therefore regarded as an effective growth regulator for inducing staminate flowers efficiently, without adverse effects on pollen viability, seed productivity or germinability.
