Polyploid speciation is one of the most important evolutionary processes in plants; that involves interspecific crosses, fertile hybrid development, chromosome doubling and diploidization. Unreduced gamete formation via meiotic restitution, as seen in the genus Triticum , plays a major role in producing allopolyploid species. Namely Bread wheat has experienced two steps of meiotic restitution occurring in amphihaploid hybrid plants with AB and ABD genome. It was known that meiotic restitution is influenced by gene(s) via changing the meiotic behavior and cause to formation of unreduced gametes. Besides, meiotic behavior of plant chromosomes influences by environmental conditions including temperature, light and soil. In this study meiotic behavior and chromosome characteristics of eight genotypes of tetraploid and synthetic hexaploid wheats possessing different level of meiotic restitution were compared. In addition, two populations of tetraploid hulled wheat, two genotypes of rye and one cultivar of triticale were used. Also "Chinese Spring" wheat cultivar was used as control. These genotypes were grown in autumn and winter planting date. When the spikes were at suitable stage of meiotic division; immature spikes were harvested, fixed in carnoy solution, stained with hematoxilin and observed under light microscope. For karyotype analysis the root-tips of seedlings were pretreated with ?-mono-bromonaphtalene, fixed in Lewitsky solution, hydrolyzed in 1N sodium hydroxide, stained with hematoxilin, squashed and ultimately observed under light microscope. The results of meiotic deliberations indicated that the samples that had planted in autumn season, facing natural conditions, possessed normal meiotic behavior with the exception of a few abnormalities. On the other hand, samples of winter planting, due to high temperature at the flowering period, possessed higher meiotic aberrations like laggards, chromosome stickiness, micronucleus, abnormal cytokines, chromatin pulling and meiotic restitution. Rye genotypes had the least amount of meiotic abnormalities (0% in autumn planting samples and 2% in winter planting samples) while triricale genotype had the most abnormalities (60% in autumn planting samples and 92% in winter planting samples). In addition, meiotic restitution topicalities like dyad and triad formations were seen in two genotypes of tetraploid wheats, which had been under temperature stress. It concluded that high temperature could affect and increased formation of unreduced gamete. The results of karyotype analysis of the genotypes indicated that the total length of chromosomes significantly differed among tetraploid wheats. It could be attributed to the chromosomes fixed at different stages of mitosis. However these genotypes did not have any significant variation for centromere index and arm