Plant husbandry – Process
Patent
1994-11-03
1997-09-09
Benzion, Gary
Plant husbandry
Process
47DIG1, 800200, 4351721, 435430, 4354301, 71 7, A01H 300, A01H 400
Patent
active
056643683
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for developing novel type of plants which are capable of fixing nitrogen also in their leaves.
It is known that nitrogen is the main limiting factor of agricultural plant cultivation since the supply of nitrogen by fertilization is albeit efficient but very expensive and is accompanied by an extreme environmental pollution. The worldwide spreading conception of cultivation, the conception of "maintainable development" gives preference to the production based on internal resources instead of using external ones. Accordingly, it is suitable to provide the nitrogen supply of plants by utilizing the possibilities implied in the biological nitrogen-fixation instead of employing fertilizers [Plant and Soil 141, 1-12 (1992)]. However, only some procaryotes (diazotrophs) are able to fix the atmospheric nitrogen gas.
The so-called aerobic nitrogen-fixing bacteria, the members of genera Azomonas, Azotobacter, Beijerinckia and Derxia belonging to the family of Azotobacteraceae [Bergey's Manual of Determinative Bacterology, 8th ed., Williams and Wilkins, Baltimore, page 253 (1974)], which are capable of an efficient nitrogen-fixation even at atmospheric oxygen levels, are unable in the nature to be incorporated into the inner tissue spaces of plants [Azotobacteraceae: the Taxonomy and Ecology of the Aerobic Nitrogen-fixing Bacteria, Academic Press, New York (1979)] and to spread in the intercellular spaces although it could be proven that, when settling down on the roots or on the outer surfaces of leaves, these species are capable to provide the nitrogen demand of some plants to a significant or whole extent [J. Gen. Microbiol. 71, 103-116 (1972); J. Gen. Appl. Microbiol. 25, 261-271 (1979); Can. J. Bot. 69, 2296-2298 (1991)]. The so-called microaerophilic diazotrophs, fixing the nitrogen at low oxygen levels, are only able to form intercellular endosymbioses [Nitrogen-fixing Bacteria in Nonleguminous Crop Plants, Sci. Tech. Publishers/Springer-Verlag, Madison, Wis., pp. 84-88 (1987)] which, however, can fix nitrogen gas only in the roots, i.e. far from the site of photosynthesis.
Up to the present, two studies have been carried out to cocultivate Azotobacter species with plant cells under in vitro conditions.
In the first experiment [Nature 252, 393-395 (1974)] an adenine-auxotrophic Azotobacter vinelandii mutant strain was cocultivated with carrot cells on a sucrose-containing medium, which was nitrogen-free or contained nitrogen in an amount insufficient for plant growth. The thus-obtained mixed callus cultures kept growing for 18 months, showed nitrogen-fixing activity and the bacteria could be observed among the living plant cells. This method has, however, several drawbacks: an auxotrophic mutant strain of Azotobacter species is used which is difficult to isolate due to its high number of "chromosomes" [J. Bacteriol., 138, 871-877 (1979)]; the growth of the cultures is slow; the system is unstable in the presence of nitrogen; no plant could be regenerated; the applicability of the method is limited to a few intensely studied species because of the low number of auxotrophic strains.
In the other experiment [Z. Pflanzenphysiol. 95, 141-147 (1979)] the bacteria engulfed the plant tissue and destroyed it. Thus, it became impossible to cultivate for a long period and to develop a nitrogen-fixing plant.
The aim of the present invention is to eliminate the drawbacks of the processes known in the art and to develop a process, by the use of which it becomes simply possible to develop under in vitro conditions a plant capable of nitrogen-fixation by its leaves also and containing bacteria belonging to the Azotobacteraceae family in its inner spaces, too.
The invention is based on the recognition that under in vitro conditions it is possible to incorporate prototrophic, rapidly growing bacteria belonging to the family of Azotobacteraceae, which are capable of nitrogen-fixation even at atmospheric oxygen levels, to the inner plant spaces and to colonize them in the inner spaces when nutr
REFERENCES:
Carlson et al. "Forced association between higher plant and bacterial cells in vitro." Nature 252:393-395 Nov. 29, 1974.
Linsmaier et al. "Organic growth factor requirements of tobacco tissue cultures." Physiologia Plantarum 18: 112 1965.
Benzion Gary
Piacfejlesztesi Alapitvany
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