Untersuchungen über die Wirkung von Stoffwechselprodukten, insbesondere Auxinen, des wachstumsfördernden Rhizobakteriums (PGPR) Bacillus subtilis auf die pflanzliche Salztoleranz

Dissertation

zur Erlangung des akademischen Grades
doctor rerum horticulturarum
(Dr. rer. hort.)

eingereicht an der
Landwirtschaftlich-Gärtnerischen Fakultät

von
Dipl. Agrar- und Gartenbauingenieur
Archontia Stavropoulou
geboren am 27. Februar 1971 in Serres

Dekan: Prof. Dr. Uwe Jens Nagel

Gutachter:
1. Prof. em. Dr. Dr. h. c. Helmut Bochow
2. Dr. Klaus-Dieter Hentschel
3. Dr. agr. habil. Bernd Freier

Datum der mündlichen Prüfung: 15.07.2005

Summary

Stavropoulou, Archontia: Studies about the action of metabolites, especially auxins, of the growth-promoting rhizobacterium (PGPR) Bacillus subtilis on the plant salt tolerance

102 pages, 33 figures, 13 tables

Humboldt University of Berlin, Faculty of Agriculture and Horticulture, Ph. D. thesis

To find out the mode of tolerance increasing action against salinity of the plant root colonizing PGPR Bacillus subtilis, bacterial metabolites of the strains FZB24 and FZB41 were studied in the test plant tomato under the influence of high salinity.

Because the culture filtrate of the fermentative transitionphase with the whole range of produced metabolites by B. subtilis showed to a certain extent a tolerance increasing action at dilution of 0,1 % in axenic plant growth tests with the parameters length, fresh mass and dry mass of shoots and roots as well as foliage area after 7 days treatment of tomato seedlings and subsequent cultivation under high salt stress, it has been fractionated with adsorber resin and HPLC. These fractions, as well as fractions from the culture filtrate after 19 h fermentation were tested also by tomato seedlings in axenic culture. Fractions with different proteins and peptides, which were produced by B. subtilis, showed partly activities also depending of concentration with regard to the plant growth stimulation and at the same time tolerance increase against salt stress. Following also a peptide extract from B. subtilis with special concentrated peptides was examined in the axenic plant test system, showing similarly a visible action depending of concentration.

In the same axenic test system there were tested further auxin precursors and auxin itself, which are known metabolites of B. subtilis, on tomato seedlings both by root treatment and leaf treatment. Additionally was studied the action of auxins on the water content of the seedlings under salt stress, as well as on the adventitious root formation with parameters rate of rooting, root number and root length of hypokotyl segments from etiolated tomato seedlings, in presence and absence of salinity. Finally it was studied the uptake and transport of auxins in segments of stems from etiolated tomato seedlings in presence and absence of salinity by means of enzyme-linked immunosorbent assay (ELISA).

Lastly it was tested the action of auxins on plant growth with calculations of the fresh and dry mass of shoots and roots, length of shoots and foliage area, as well as of water content in a tomato hydroponic cultivation under greenhouse conditions and salt stress.

The results show that particularly auxin precursors and partly auxin as metabolites of B. subtilis can induce an increase in the salt stress tolerance of the test plant tomato, although the action on the plant salt tolerance was differentiated and variable in its extent.

The existing effect firstly of the auxin precursors is discussed as obviously main mechanism for the plant growth stimulating and at the same time tolerance increasing action of the rhizobacterium against salinity by root colonization and interaction with the plant metabolism.

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