Developmental regulation of K accumulation in pollen, anthers, and papillae: are anther dehiscence, papillae hydration, and pollen swelling leading to pollination and fertilization in barley (Hordeum vulgare L.) regulated by changes in K concentration?

The presence of potassium (K) in pollen, anthers and papillae from barley (Hordeum vulgare L.) flowers with different levels of developmental stages starting from boot stage to fully mature flower, was studied by using the K-sensitive fluorescent dye PBFI (potassium-binding benzofuran isophthalate) and confocal laser scanning microscopy. The presence of heavy K fluorescence was detected only at the aperture area of the mature pollen. Similarly, the presence of K increased with the progression from immature to mature anther and papillae. In addition, a higher concentration of K was observed only at the stomium area (the place of anther dehiscence) of mature anthers. Keeping in view the role of K as an active osmoticum and the consistent and synchronized appearance of K in mature pollen, anthers, and papillae, it was concluded that K may regulate anther dehiscence, pollen imbibition, and papillae hydration leading to pollination and fertilization.