Endophyte transmission and activity in the Anabaena-Azolla association |
| |
Authors: | J H Becking |
| |
Institution: | (1) Department of Soil Science and Plant Nutrition, Agricultural University, De Dreijen 3, 6703 BC Wageningen, The Netherlands;(2) ITAL, Research Institute of the Ministry of Agriculture and Fisheries, P.O. Box 48, 6700 AA Wageningen, The Netherlands |
| |
Abstract: | Summary The survival of Azolla was studied in an artificial system which simulated the soil/water interface and the desiccation of
soil during a fallow period in lowland rice culture. Tests with non-sporulating and sporulating Azolla fronds showed that
Azolla only survives with sporulated fronds. At their reappearance the Azolla fronds already harboured the Anabaena endophyte.
A detailed light microscopic and transmission electron microscopic study of macro- and micros-porocarp formation and development
revealed that the endophyte is transmitted by the macrosporocarps and not by the microsporocarps. The Anabaena cells within
the macrosporocarps are found just below the indusium cap. These cells are not nitrogen-fixing akinetes. The free-living Anabaena
cells at the stem apex and below the overarching developing leaves do not bear heterocysts and accordingly are non nitrogen-fixing.
During the development of the leaf the Anabaena enters the leaf cavity, but later the pore of this, cavity closes and the
imprisoned cyanobacteria are lysed before the leaf decays. As the Azolla leaves age a nitrogen-fixing capability is successively
built up concomittantly with the production of heterocysts. Heterocyst frequencies of 40–50% can be found inAnabaena azollae. Usually a gradient of nitrogen-fixing capacity occurs along the Azolla rhizome with two distinct peaks at leaf number 7/8
and at leaf number 13/14 from the apex. |
| |
Keywords: | Anabaena azollae Azolla Desiccation Macrosporocarps Microsporocarps Nitrogen fixation Sexual reproduction Survival Azolla |
本文献已被 SpringerLink 等数据库收录! |
|