Mechanism of septum opening in anthers of two-rowed barley (Hordeum vulgare L.)

To test the hypothesis that the rapid swelling of pollen grains driven by potassium movement opens the septum in anthers of poaceous plants, we studied (1) the behaviour of pollen grains during unfolding of the locule and (2) the distribution of potassium in the locule in two-rowed barley. In the first experiment, the unfolding of decapitated anthers was observed. The pollen grains paved the inner wall of the locule during the unfolding process, suggesting that the pollen grains bend the locule wall outward when they adhere to the wall. In the second experiment, the distribution of potassium in transverse sections of locules in dehisced and indehisced anthers was observed. In indehisced anthers, potassium was detected outside the pollen grains. In contrast, in dehisced anthers, potassium was detected inside pollen grains. This suggested potassium ions moved From the inter-pollen space (locular fluid) into the pollen grains in the locule at the time of pollen-grain swelling. (C) 2000 Annals of Botany Company.