Plants exhibit two phases in their life cycle:
i) Gametophytic: Gamete bearing, haploid stage is predominant
ii) Sporophytic: Spore bearing, diploid stage is predominant
Ploidy is the number of sets of chromosomes in a cell or cells of the organism. Gametophyte is the phase which has haploid number of chromosomes and produces gametes. Sporophyte is the plant body which produces spores. Spores form the gametophyte. Hence, cells of gametophyte are haploid and cells of sporophyte are diploid. Both spores and gametes are single celled and haploid.