Construction of RNAi Expression Vector Targeting FaVRN1 Gene in Tall Fescue

[Objective] This study was to construct RNAi expression vector targeting FaVRN1 gene. [Method] A 145 bp Arabidopsis actin intron was inserted into the expression vector to generate an intermediate vector pBI121-M-INT. And then two pairs of specific primers with enzyme restriction sites spanning a 351 bp cDNA conserved sequence fragment of FaVRN1 gene were designed for RT-PCR to construct RNAi expression cassette. The amplified fragment was inserted forwardly and reversely at two sides of the intron to construct an RNAi expression vector with hairpin structure. [Result] Double enzyme digestion（HindIII＋BamHI） showed the intron had been successfully into the vector pBI121. PCR amplification and double enzyme digestion indicated the success of forward and reverse ligation of target FaVRN1 fragment into the intermediate vector. [Conclusion] This study laid foundation for breeding novel flowering-inhibited tall fescue varieties.

Existence of homologous sequences corresponding to cDNA of the ver gene in diverse higher plant species

The presence of DNA homologues corresponding to verc203 (vernalization-related cDNA clone) was investigated by molecular hybridization techniques. The genes were detected in 16 plant species that cover 12 subclasses of the Takhtajan system of angiosperms classification including diverse model species. The results of Southern blot analysis showed a low copy number of this gene existed in rice, wheat, barley and Arabidopsis. The hybridization result of PCR products demonstrated the conservation of the gene corresponding to ver203 in diverse plants. The phylogenetic tree of the ver203 gene in tested plants was supported by evolution relationship of species. The ver203 gene expressed in a vernalized plumule winter wheat, instead of the root. And the endosperm before the treatment was essential for the ver203 expression during vernalization in wheat. In Arabidopsis thaliana, the pattern of expression showed that the gene corresponding to ver203 was expressed at low temperature for 14 days. Gibberellin(GA3) may accelerate the expression of ver203 gene in Arabidopsis exposed to low temperature. However, it could not replace vernalization treatment to initiate the gene expression.

INFLUENCE OF SPRING EQUATORIAL EASTERN PACIFIC SSTA ON THE SEASONAL CHANGE FROM SPRING TO SUMMER OF EASTERN ASIAN CIRCULATION

Based on the analysis of NCEP height, wind and OLR data, the influence of spring equatorial eastern Pacific SSTA on the seasonal change from spring to summer of eastern Asian circulation has been investigated. Results show that related to the warm (cold) spring SSTA in the equatorial eastern Pacific, the anomalous anticyclone (cyclone) circulation emerges around the South China Sea and the Philippines, the strong (weak) west Pacific subtropical high locates to the west (east) of its normal position, which induces to the late (early) onset of the South China Sea monsoon. The numerical simulations have also shown that the remarkable influence of spring SSTA in the equatorial eastern Pacific on the spring seasonal change of eastern Asian circulation will last till summer.

Effects of Forest Type and Urbanization on Carbon Storage of Urban Forests in Changchun, Northeast China

Rapid urbanization has led to dramatic changes in urban forest structures and functions, and consequently affects carbon(C) storage in cities. In this study, field surveys were combined with high resolution images to investigate the variability of C storage of urban forests in Changchun, Northeast China. The main objectives of this study were to quantify the C storage of urban forests in Changchun City, Northeast China and understand the effects of forest type and urbanization on C storage of urban forests. The results showed that the mean C density and the total C storage of urban forests in Changchun were 4.41 kg/m2 and 4.74 × 108 kg, respectively. There were significant differences in C density among urban forest types. Landscape and relaxation forest(LF) had the highest C density with 5.41 kg/m2, while production and management forest(PF) had the lowest C density with 1.46 kg/m2. These differences demonstrate that urban forest type is an important factor needed to be considered when the C storage is accurately estimated. Further findings revealed significant differences in different gradients of urbanization, and the mean C density decreased from the first ring(6.99 kg/m2) to the fourth ring(2.87 kg/m2). The total C storage increased from the first ring to the third ring. These results indicate that C storage by urban forests will be significantly changed during the process of urbanization. The results can provide insights for decision-makers and urban planners to better understand the effects of forest type and urbanization on C storage of urban forests in Changchun, and make better management plans for urban forests.

ABRUPT CHANGES OF THE WESTERN PACIFIC SUBTROPICAL HIGH AND ITS INTERANNUAL VARIATION DURING LATE SPRING AND EARLY SUMMER

The 500-hPa geopotential height data used in this paper are from NCEP/NCAR data set for the period from 1979 to 1996 (from March to July). Using pentad average, we define the intensity, westernmost ridge point and mean latitude of the subtropical high ridge. Then the wavelet transform and EOF analysis are performed. It is found that there mainly exist three interseasonal abrupt change processes, which correspond to the onset time of the South China Sea Summer Monsoon (SCSSM), the beginning and the end of the Mei-yu respectively. The interannual variation of the subtropical high in late spring and early summer presents quasi-4-year and 8-year periods.

画草原

敖包前，小河边，支起画架画草原。水有多绿草原就有多绿，天有多蓝哈达就有多蓝。