申論題

八 、In 1888, German agricultural chemists Hermann Hellriegel and Hermann Wilfarth discovered that root nodules can convert nitrogen from the air into ammonia. Root nodules are specialized structures formed by leguminous plants to facilitate nitrogen fixation by nitrogen-fixing bacteria. Certain species of cyanobacteria, such as Anabaena spp.(念珠藻), can also perform nitrogen fixation, but they do so through heterocysts instead of forming root nodules. As a result, cyanobacteria like Anabaena can carry out nitrogen fixation independently and live autonomously. (1) Why do symbiotic rhizobium bacteria in legumes' roots need to carry out nitrogen fixation? (2) Why can heterocysts of cyanobacteria perform nitrogen fixation independently? 10%