[CO2 flux characteristics and their influence on the carbon budget of a larch plantation in Maoershan region of Northeast China].

From January to December 2008, the CO2 flux in a larch plantation (Larix gmeilinii) in Maoershan region of Shangzhi County, Heilongliang Province was measured by eddy covanance method, and the diurnal changes of leaf photosynthetic rate were measured in growth season (from May to October). There existed differences in the net ecosystem exchange (NEE) of the plantation in different time periods under the effects of environmental factors. In the afternoon (12:00-24:00), the NEE changed more slowly with the variation of vapor pressure deficit (VPD) than in the morning (0:00-12:00); and in the morning, tbe light use efficiency was 0.6284 mol x mol(-1), 14% more than that in afternoon. The NEE increased with increasing temperature, and the increment in the morning was 50% higher than that in the afternoon (air temperature > 15 degrees C). These differences in responding to environmental changes led to 88% NEE implemented in the morning, and only 12% NEE implemented in the afternoon. The annual gross ecosystem productivity (GEP) in the morning took a percentage of 60%, and that in afternoon took 40%. These findings were supported by the observation at leaf level, i.e., on average of whole growth season, the leaf photosynthetic capacity in the morning was over 2-fold higher than that in afternoon. Generally, the annual NEE, ecosystem respiration (Re), and GEP of the plantation in 2008 were 263-264 g C x m(-2), 718-725 g C x m(-2), and 981-989 g C x m(-2), respectively.

[Expression of two plant agglutinin genes in transgenic tobacco plants].

A plant expression vector pBACG containing the DNA sequence coding for Amaranthus caudatus agglutinin (ACA) and a modified Glanthus nivalis agglutinin (GNA) gene was constructed. Leaf explants of Nicotiana tobacum cv. SRI were transformed with A. tumefaciens LBA4404 harbouring the above expression vector. Results from PCR and Southern blotting analysis showed that both the ACA and GNA gene were inserted into the genome of transformed tobacco plants. Western blottingting analysis of soluble protein isolated from transgenic plants showed that ACA and GNA were synthesized. The results from insect bioassay with peach aphids ( Myzus persicae) revealed that the transgenic plants of pBACG had acquired high resistance against peach aphids. The average aphid-inhibition rate reached up to 83.9% and 85.3% for transgenic plants (T0) and their selfed progenies (T1) respectively,indicating that the functions of these two genes were inheritable.

[Cloning of ACA gene promoter and preliminary study of its function].

Using total DNA isolated from Amaranthus caudatus as the template, a DNA fragment of about 700bp upstream of the coding sequence of Amaranthus caudatus agglutinin (ACA) gene was amplified by TAIL-PCR and cloned. To examine the regulatory function of this DNA fragment, it was inserted into a plant expression vector containing GUS gene to substitute the CaMV 35S promoter and the resulted recombinant plasmid was designated as pBpAG. The expression vector pBpAG was transferred to different tissues of plants, via Agrobacterium-mediated transformation in vacuum condition. Transient expression of GUS in the transformed tissues was detected by histochemical GUS staining and the results showed that the GUS activity was expressed specifically in seeds. These preliminary results indicate that this DNA fragment upstream of the ACA coding sequence could very possibly be a promoter with seed specificity. Some putative cis-elements within the promoter were discussed.