Charles F. Kettering Research Laboratory, Yellow Springs, Ohio 45387.
Plant Physiol. 1974 Jun;53(6):813-9. doi: 10.1104/pp.53.6.813.
Cultures of Azolla caroliniana Willd. free of the symbiotic blue-green alga, Anabaena azollae, were obtained by treatment of Azolla fronds with a regimen of antibiotics. These symbiontfree plants can be maintained only on medium containing a combined nitrogen source.Morphological aspects of the symbiotic association show the confinement of the Anabaena azollae within the leaf cavity of the Azolla. Procedures were established for the isolation of pure preparations of Anabaena azollae and Azolla chloroplasts. It has not yet been possible to grow the isolated alga in independent culture.Photochemical activities of the isolated alga and fern chloroplasts were measured by spectrophotometric assays for photosystems I and II as well as by P700-content (photosystem I) and delayed light emission (photosystem II). In the algal fraction, both photosystems were repressed when compared to freeliving Anabaena cylindrica, but the relative ratio of photosystem I to photosystem II may be appreciably greater in Anabaena azollae. Azolla chloroplasts were generally comparable to spinach chloroplasts.A comparison of the chlorophyll a and b content of Azolla fronds with and without the symbiotic alga resulted in an estimate that in the symbiotic association, the Anabaena azollae accounts for from 7.5 to 15% of the total chlorophyll.
卡罗来纳浮萍（Azolla caroliniana Willd.）的共生蓝藻，鱼腥藻（Anabaena azollae）被抗生素处理去除后，可获得无菌培养物。这些无共生体的植物只能在含有混合氮源的培养基上维持生长。共生关联的形态学方面表明，鱼腥藻被局限在浮萍的叶腔中。已经建立了分离鱼腥藻和浮萍叶绿体的纯培养物的程序。迄今为止，还无法在独立培养中生长分离的藻类。通过分光光度法测定光合系统 I 和 II 的光化学活性以及 P700 含量（光系统 I）和延迟发光（光系统 II），测量了分离藻类和蕨类叶绿体的光化学活性。与自由生活的鱼腥藻（Anabaena cylindrica）相比，藻类部分的两个光系统都受到抑制，但鱼腥藻中光系统 I 与光系统 II 的相对比值可能明显更高。浮萍叶绿体通常可与菠菜叶绿体相媲美。比较有共生藻和无共生藻的浮萍的叶绿素 a 和 b 含量，估计在共生体中，鱼腥藻占总叶绿素的 7.5%至 15%。
