Growth of maize seedlings under seed treatment with the exometabolites of Streptomyces

 

Maslobrod, S, Burtseva, S*, Сorlateanu, L, Postolatii, O*, Ganea, A,  Namolovan, L*

                          

Institute of Genetics and Plant Physiology, Academy of Sciences of Moldova, Chishinau 

*Institute of Microbiology and Biotechnology, Academy of Sciences of Moldova, Chishinau 

 

Earlier we have shown that exometabolites (EМ) of soil microorganisms from Streptomyces gender significantly influence on primary processes of seed metabolism (Maslobrod etc., 2005). The effect depends on genotype of the object, on Streptomyces species and solution concentration of their EM. By the example of maize, tobacco and tomato seeds it was shown the stimulating action of EM of Streptomyces with concentration 1: 200. The effect increased under the treatment of Streptomyces with the millimeter irradiation (MMI) of 5.6 mm with power density (PD) 10 mWt/cm2 and expositions for several minutes (Maslobrod etc., 2005, 2006).

       It was interesting to investigate how exometabolites (EM) influence on seed germination under other regimes of treatment of Streptomyces with MMI and with the use of EM after their long-term storage.

       Streptomyces strain S. canosus CNMN-71 was grown on ChapekÕs agar medium within 10 days. Then the object was exposed to MMI irradiation of 5.6 mm with PD 0; 2.4; 4.7; 6.6; 8.5 and 10.4 mWt/cm2 with the exposition for 5 minutes, which has stimulating effect for microorganisms and plant seeds (Maslobrod etc., 2005). Further it was cultivated on liquid medium М1 (basic source of carbon - maize flour) within 5 days, and after that biomass was separated from culture liquid by centrifugation. The EM complex was used as regulator of maize seed growth (hybrid Debut). Controls were seeds soaked in distill water and in native solutions of EM (concentration 1: 200), which were received after MMI irradiation of the initial Streptomyces strain. The number of seeds for each variant - 100 seeds. Seeds were germinated in thermostat at 25оС within 4 days. Earlier in the same experiment it was revealed the essential increase of output of Streptomyces biomass in the variant of their MMI treatment with PD 4.7 and 8.5 mWt/cm2 and the decrease of output of biomass with PD 10.4 mWt/cm2 (accordingly, in mg/l – 6.22; 5.9; 4.48 with the control 5.39). At the same variants the increase and decrease of the length of coleoptiles and rootlets of maize seedlings of haploid form was accordingly received with the use of EM solutions right after isolation of EM (Burtseva etc., 2006).

       In this report the results of the use of EM solutions (in concentration 1 : 200) after the long-term storage of EM (within 6 months) at +4оС are presented.

For storage both native EM and EM, subjected to pasteurization, were taken. In control experiment with the use of EM right after their isolation, the data were received, which were essentially similar to the former data (Burtseva etc., 2005).

             The following basic results were received (table):

1) When the seeds were soaked in solutions of EM of Streptomyces, which were not subjected to MMI influence, the essential influence of soaking on seed germination was not revealed;

 2) Treatment of Streptomyces by MMI with various PD promotes to receive essential distinctions between variants; at that, native and pasteurized exometabolites also essentially differ among themselves;

 3) Exometabolites in native state showed the nonlinear character of change of seedling parameters: on coleoptiles – stimulation with PD 2.4 and 8.5 mWt/cm2 and the absence of inhibition on other variants; on rootlets – the absence of stimulation and the essential inhibition at 4.7 and 10.4 mWt/cm2;

 4) Pasteurized exometabolites showed practically linear character of change of seedling parameters with their gradual decrease in the process of growth of PD value. 

       Thus, after the long-term storage exometabolites have certain physiological activity. For native EM this activity coincides with the activity peculiar to EM in initial state (right after isolation) on variants of stimulation with PD 8.5 mWt/cm2 and of inhibition with PD 10.4 mWt/cm2 (table). The application of pasteurized EM leads to inhibiting effect.

       It is possible to suggest that under the long-term storage in pasteurized exometabolites there occur qualitative and quantitative changes in the ratio of growth-regulating substances, in particular, substances of the phytohormonal nature (auxins, gibberellins), essential and protein-synthesizing amino acids, and also water-soluble vitamins of group В.

 

Table

Influence of pre-sowing soaking of maize seeds (hybrid Debut) in solutions of exometabolites (EM) of Streptomyces on the seedling growth

 

 

PD of MMI irradiation, mWt/cm2

 

EM state after the long-term storage

Native EM

Pasteurized EM

Length, mm

Coleoptiles

Rootlets

Coleoptiles

Rootlets

0

21.3±2.1

82.4±5.0

33.1±3.3

95.4±9.6

2.4

28.8±2.5

89.9±7.1

28.9±5.6

81.9±2.3

4.7

23.8±3.2

57.0±2.4

27.9±7.8

71.4±8.7

6.6

18.7±2.3

75.5±9.6

22.0±6.5

62.4±13.6

8.5

30.4±2.6

82.6±10.3

15.6±6.2

57.2±11.0

10.4

24.2±5.9

48.5±6.5

24.4±4.6

61.8±8.3

 

  Note: when the seeds were germinated in distill water the length of the coleoptiles was

 25.4±2.6 mm, and the length of the rootlets – 104.9±10.0 mm