Evolutional trends of leaf stomatal and photosynthetic characteristics in wheat evolutions

According to the evolutional relationships among wheat varieties, 21 wheat varieties were chosen as research materials in this experiment to determine the evolutional trends of stomatal and photosynthetic characteristics. The results showed that as ploidy increased, the stomatal length, width, perimeter and area were found to increase. The stomatal density was found to decrease in A, B, D genomes, while no differences were found in stomatal indices among ploidies, indicating that the stomata became larger, but were still less in evolution progress. The Diploidy had the highest Pn, which was less in Tetraploidy, and the least in Hexaploidy. On the contrary, the Hexaploidy had the highest value in Fv/Fm, and the Diploidy had the highest chlorophyll content. The net photosynthetic rate had significant correlation with stomatal conductivity, while no significant relationship was found between stomatal conductivity and any stomatal characteristics, indicating that the stomatal conductivity is one of the factors limiting the photosynthetic rate, while the single stomatal characteristics is not the reason inducing the change in photosynthetic rate. The stomatal density showed significant differences among ploidy materials in A, B, D genomes, and the trend of genotype was in order of 2n > 4n > 6n; the stomatal length, width, perimeter and area showed significant differences among ploidy materials, and the trend of genotype was in order of 6n > 4n > 2n. The results indicated that the low density might induce low conductivity and low photosynthetic ability in Hexaploidy. Furthermore, the Diploidy had higher value in chlorophyll content of flag leaf area among ploidy materials in A, B and D genomes, indicating that higher chlorophyll content might be the reason for higher photosynthetic ability in Diploid wheat species.