Li Maosong

Differences in stomatal and photosynthetic characteristics of five diploidy wheat species

Abstract Five diploidy wheat species were chosen as research materials to determine the differences in stomatal and photosynthetic characteristics. The results of the study showed that species with S genomes ( Ae . Sect . Sitopsis ) had the largest values in stomatal length, girth and area, and the lowest values in stomatal width, density and index. On the contrary, the species with D genomes ( Ae . Tauschii ) had the highest values in stomatal width, density and index, and the lowest values in stomatal length, girth and area. The net photosynthetic rate ( Pn ) and stomatal conductance ( Gs ) were higher in species with D genomes ( Ae . Tauschii ) and lower in species with S genomes ( Ae . Sect . Sitopsis ), respectively. The net photosynthetic rate showed significant correlation with stomatal conductivity, and the changes in intercellular CO 2 content showed the opposite trend to the changes in stomatal limitation, indicating that the stomatal conductivity is the main factor limiting the photosynthetic rate. T . urartu with higher net photosynthetic ability showed higher values in stomatal conductivity and stomatal limitation, and lower values in intercellular CO 2 content. However, T . boeoticum showed the opposite trend. T . urartu had higher values of chlorophyll content in flag leaf area, while T. boeoticum had lower values, indicating that there might be higher chlorophyll content.

Evolutional trends of leaf stomatal and photosynthetic characteristics in wheat evolutions

Abstract 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.

Changes of Chinese Beginning Date of Vegetation Greenness Period Based on NOAA NDVI

Beginning date of greenness period of vegetation(BGP)is closely related to seasonal dynamics of the lower atmosphere and is therefore an important variable in influences and feed-back mechanisms of global climate variation to terrestrial ecosystem.Detecting BGP using remote-ly sensed data at regional or global scales has become an advanced topic in geography and ecolo-gy.Based on the processed NOAA/AVHRR NDVI data,the study is to use Logistic fitting model on cumulative frequency of NDVI to compute BGP of China by pixels from 1982 to 1999,count the annual average BGP of every vegetation type and bio-climate district,and analyze the inter-annual change trends,spatio-temporal dynamic change feature of BGP of various spatial types.The results indicate that:(1)BGP have an advance trend in most regions and obviously advance in North China Plain,northeast Guizhou,the middle and south Hunan,west Guangxi and typical grassland area of east Inner Mongolia.(2)The regions in which inter-annual fluctuation of BGP are over 10 days are mainly distributed in the area covered with agricultural vegetation types,the areas covered with evergreen vegetation types and the areas covered with steppe vegetation types.Thereinto,the fluctuation of BGP in Hetao plain,Guanzhong basin,east Henan,west Sichuan basin,Guangdong,Taiwan and so on,are over 15 days.(3)BGPs of the other vegetation types ex-cept temperate desert show an advance trends.(4)With the reduction of annual accumulative tem-perature and increase of drought indices,BGP of various bio-climate areas delay.An advance of BGP is found in South China,East China,Central China,North China,Inner Mongolia,Northeast China and Tibet,whereas a delay occurred in Shaanxi,Shanxi and Northwest China.(5)BGP of all vegetation types evidently delay in 1982,1983 or 1984,which may be associated with the strong EI-Nino effect in the 1982-1983 period.