The life cycle in Spirogyra is haplontic, as dominant phase in life cycle is haploid (n) and diploid phase is represented by only zygospore and it undergoes meiosis.
Therefore, in the haplontic life cycle of Spirogyra no true alternation of distinct plants was observed. Rather, alternation of chromosome numbers from haploid to diploid and back to haploid conditions can be noticed.
