The aleurone layer performs a variety of functions to help maintain proper development of the seed. One example of this is maintaining a low pH in the apoplast. In cereals, the aleurone layer releases organic and phosphoric acids in order to keep the pH of the endosperm between a pH of 3.5 and 4. In barley, the aleurone layer also releases nitrite into the starchy endosperm and apoplast under anaerobic conditions. In addition, although the function is unclear, a certain class of hemoglobins is present in the outer layer of living cells including the aleurone tissue in barley and rice seeds.