环境因子对铜绿微囊藻7820胞外多糖的影响

研究了多种环境因子对铜绿微囊藻7820可溶性胞外多糖（extracellular polysaccharide,EPS）合成的影响.在18 d内,较高浓度的NO3^-,较高的pH和光强,均显著提高了EPS的合成,其中,NO3^-对EPS的合成影响最大,其最大产率为5.255μg·L^-1·d^-1.而KH2PO4,CaCl2,MgSO4等大量元素、以及微量元素FeCl3和EDTA对EPS的合成无明显影响;除在实验后期20℃时EPS有较大增加外,温度对其无明显影响.在各种环境因子影响下,EPS产量均随时间延长而增加.此外,NO3^-,pH和光强对铜绿微囊藻7820的生长速率和总糖的产生也有影响,在较低的NO3^-浓度、适中的pH和光强下,生长速率较高;而较高的NO3^-浓度、较低的pH和光强,其生长速率明显较低;略低的NO3^-浓度和光强可明显提高其总糖产量,而较高的NO3^-浓度和弱的光强则明显降低其总糖产量;pH对总糖的产量影响不大.微囊藻有较高的多糖积累,其EPS和总糖的合成有不同的机制

Seed banks need investors

Delegates at a recent United Nations Food and Agriculture Organization (FAO) conference in Leipzig agreed a 50-page Global Plan of Action for the Conservation and Utilization of Plant Genetic Resources for Food and Agriculture. The delegates promised to devote more effort to conserving plants both in gene banks and on farms. The report, however, only refers to funding already present, as developed countries failed to commit any further funds to assist gene banks. According to the FAO, the world needs to invest US$3 billion over the next ten years to prevent the extinction of one million varieties of agricultural plants currently preserved in badly equipped and poorly funded gene banks. More than half of the world's 1,300 stores for rare strains of cereals, vegetables and fruits are perhaps incapable at present of performing the basic conservation role of a gene bank. Some 130 countries lack long-term storage facilities, while many established gene banks report delays and problems with seed regeneration as a result of shortages of staff, funding or both. If seeds are not regenerated and fresh seeds collected every ten years, then seeds can deteriorate. Any loss of genetic diversity now will reduce the options for combating plant diseases or improving crop yields in the future. While delegates to the conference may have been disappointed that they were unable to secure further funds they were generally relieved that the global plan had been agreed. However, it was felt that in order for gene banks to continue their work and prevent loss of the material already stored in the gene banks, further action must be taken immediately. Carl Fowler FAO Viale delle Terme di Caracalla 00100 Rome, ITALYDelegates at a recent United Nations Food and Agriculture Organization (FAO) conference in Leipzig agreed a 50-pageGlobal Plan of Action for the Conservation and Utilization of Plant Genetic Resources for Food and Agriculture. The delegatespromised..