发状念珠藻对盐胁迫的响应

探讨了发状念珠藻(NostocflagelliformeBornetFlah)对盐胁迫的耐受适应机制，采用含不同浓度NaCl(0、01、02、04、06、08、10mol/L)的BG110培养液处理具有正常生理活性的丝状体，25±05℃，40μmol/m2/s下照光培养12h，测定藻体光合作用、呼吸作用等生理活性以及体内一些物质的含量，结果表明:随培养液中NaCl浓度的升高藻体光合作用、呼吸作用以及PSⅡ活性(Fv/Fm)降低；质膜透性不断增大，丙二醛含量升高，自由水含量、自由水/束缚水比值下降，类胡萝卜素、可溶性糖含量增加，脯氨酸含量变化不大。由此可知，盐胁迫下发状念珠藻正常生理活性受到抑制而表现出一定的抗逆能力；该藻对盐胁迫具有一定的耐受能力，类胡萝卜素的增加有助于清除藻体内的氧自由基，可溶性糖可能是其主要渗透调节物质之一，脯氨酸在盐胁迫中的渗透调节作用不大。  

RESPONSE OF NOSTOC FLAGELLIFORME TO SALT STRESS

Nostoc flagelliforme (Berk. Curtis) Born. et Flah. is a terrestrial filamentous nitrogen-fixing cyanobacterium that is distributed in Algeria, China, France, Czech, Slovakia, Mexico, Mongolia, Morocco, Russia, Somalia and USA. It is distributed on northern and northwestern parts of China and has been used as a health food and herbal medicine by Chinese and other Asian populations over centuries. Mass culture of N. fiagelliforme in an engineered system is sought but has not been available, due to the lack of understanding the resistance mechanism and growth physiology of the organism under extreme variable environments. Arid and semiarid steppe is the habitat of this alga in China and alkaline soil is the main growth substrate. It is interesting that the alga can survive and grow in such atrocious soil. This paper was conducted to study the effect of salt stress on this terrestrial alga. The modified BG11 0 culture medium containing different NaCl concentration: 0, 0.1, 0.2, 0.4, 0.8 and 1.0 mol/L, were used to culture algal mats. Algal mats were kept in BG11 8-11h before experiment for physiological recovery. The algal physiological activity and some special substance, such as MDA, polysaccharides, carotenoid and proline, were tested after 12h treatment under 25±0.5℃,40μmol/m 2/s. The results indicated that NaCl stress reduced net photosynthesis, respiration and PSⅡ activity. When NaCl in medium is beyond 0.2mol/L, there were marked decrease in net photosynthesis, respiration and photochemical efficiency. Due to salt stress, permeability of plasma membrane, MDA contents (the production of lipid peroxidation), carotenoid content and polysaccharides content increased, free water content (FWC) and FWC/BWC (bound water content) decreased, while proline content did not change, it meant there is no significant effect of proline in this alga to response to high salt stress. It could be concluded that algal physiological activity was inhibited under salt stress, high salt concentration can lead to increase in the lipid peroxidation and ralative permeability, alter the pigments and influence algal physiological function. On the other hand, this alga also had a certain extent resistance ability to salt stress. Content of carotenoid and polysaccharides were increased to eliminate free radical and regulate osmotic pressure, respectively