Сельскохозяйственная биология, 2010, № 3, с. 102-107.

УДК 633.16:577.175.1:631.811.93

GROWTH OF SPRING BARLEY AND ACTIVITY OF ENDOGENOUS PHYTOHORMONES UNDER THE INFLUENCE OF SILICON COMPOUNDS

V.N. Lozhnikova¹, I.V. Slastya²

In the conditions of laboratorial and field microallotment experiments the authors studied the effect of organic (tetraethoxysilane) and inorganic (sodium silicate) silicon compounds on activity of endogenous phytohormones and the growth of spring barley of the Preriya and Kamyshinskii 23 variety. The positive influence of seed treatment by silicon compounds on the growth of two varieties plants and content of endogenous phytohormones was established.

Key words: silicon, barley, plant growth, endogenous phytohormones.

Pre-sowing treatment of seed is one of the most cost-effective methods of increasing productivity of agricultural crops. Currently, along with traditionally used protective preparations against plant diseases and pests, the biologically active substances stimulating plant growth, increasing plant resistance to unfavorable factors, promoting the higher yield and its better quality are being increasingly applied.

A biological activity has been established for many chemical compounds including silicon-containing ones. The organic-silicon compounds are used as components of preparations for treatment of seed and sowing (mival, migugen, ekosts). Inorganic silicon compounds are used mainly as fertilizers, and their high efficiency was proved for many plant cultures, especially the silicon-accumulating crops including rice and other cereals (1-6).

It is known that plants absorb silicon via root system in the form of orthosilicic acid monomer (7), as well as low-weight molecular form of colloidal silicic acid and its ester (8). Silicon penetrates in plants as silicic acid anion (SiO₃^2-), acid molecules Si(OH)₃, Si(OH)₄ and various esters (2). Besides, silicon can be absorbed by plants through their leaves in the form of potassium silicate and sodium silicate (1).

Water-soluble silicon compounds are becoming increasingly common applied in our country and abroad, due to their high availability to plants, ease of use, low cost, less toxicity for warm-blooded animals and non-volatility. They can be used for seed treatment and spray dressings on leaves during vegetation (1, 2, 9-15). Seed treatment promotes high economic advantage, as well as a positive effect in plants starting from early stages of their development.

Many bioactive compounds affect biochemical processes and hormonal balance in plant tissues. Even small doses of phytohormones, being transported within a plant and causing certain morphological effects, regulate the intensity and direction of physiological processes.

The purpose of our work - to study the effects of silicon compounds on growth of spring barley and the activity of endogenous phytohormones.

Methods. The study was performed  on a spring barley Preriya and Kamyshinsky 23 – the varieties selected upon results of preliminary short-term laboratory tests of seedlings response to silicon treatment (16). Both varieties were created for the unsustainable farming zone and recommended for cultivation in the Lower Volga region of Russia. The barley seeds were treated with sodium silicate (inorganic form) and tetraethoxy silan (TES) – the ethyl ether of orthosilicic acid (organic form) - in concentrations of 0.4% at a flow rate of 1.2 ml solution per 100 g of seeds. A control - seeds treated with water.

Plants were grown in conditions of laboratorial and microallotment field experiments. In the laboratory, the treated seeds were germinated in water at 20-22 °C  by thermostating in the dark for 5 days, from the 5th to 10th day – under the lightening of 15 klux at 16-hour daylight (3-fold repetitions). Germination index was determined on the 7 th day, the dry matter content, biomass of roots and aboveground parts of plants - at the end of experiment (10th day).

The microallotment field experiment was carried out in 2005-2007 in the Kamyshinsky district of the Volgograd region. The soil of experimental field - chestnut loam, the allotment area - 1 мP2P. The repetition of experiments 3-fold. The aboveground biomass of plants was accounted at phases of the third leaf, tillering and booting.

Phytohormones activity in aboveground plant biomass was determined in the end of laboratorial experiment in control and in the variant with sodium silicate treatment of seeds (10-fold analytical replication). After the fixation of plant material with liquid nitrogen (auxins and gibberellins - 10 g, cytokinins - 1 g), plant hormones were extracted with 80% ethanol.

To determine the content of auxins, the extract was evaporated to water in the rotor (FC, Czech Republic), centrifuged at 6000 rpm, a supernatant was acidified (pH 3.0), 3-fold re-extracted with ethyl ether  purified of peroxides, evaporated to dryness and dissolved in 96% ethanol. Chromatography was carried out in the system isopropyl: ammonia: water (80:0,05:20). The biological activity of phytohormones was assessed by a growth of coleoptiles in wheat test-plants the variety Priokskaya (17).

The content of free gibberellins was determined after the removal of phenols with lead oxide, centrifugation (6000 rpm), evaporation to water in the rotor, acidification of a supernatant (pH 3.0), 3-fold re-extraction with ethyl acetate, evaporation to dryness and dissolution in 96% ethanol. Chromatography was performed in the system isopropyl: ammonia: water (10:1:1). Biological activity was evaluated on seedlings of dwarf pea the variety Pioner (18).

To determine the content of cytokinins, an alcoholic extract was evaporated to water in the rotor, a supernatant was acidified (pH 3.0), impurities were removed with ethyl ether, water residue made alkaline (pH 8.0). Column chromatography was performed with concentrating cartridges Seppak C 18 (“Millipor”, USA). Cytokinins column was washed with 80% ethanol. Quantitative determination of cytokinins was performed by ELISA (enzyme-linked immunoassay) method on the device Multiskan (Sweden) (λ = 492 nm) (19).

Statistical analysis was performed using programs STRAZ (variance analysis) and STATISTICA-6.

Results. Presowing treatment of seed with silicon compounds caused a benefitial effect on growth of barley plants. In the variety Preriya, both TES and sodium silicate rather stimulated the development of root system than the aboveground parts of plants (Table 1). The biomass of roots in these variants was, respectively, 26,1 and 23,7% higher than in control; the increase in weight of above-ground parts was 8.9 and 6.9%, resp.

In the variety Kamyshinsky 23, seed treatment with TES and sodium silicate caused the greater influence on growth of aboveground parts of plants – respectively, 16,2 and 10,1% higher than in control. The biomass of roots increased only in the variant of treatment with TES (at 8,7%).

 In both varieties, the variants of treatment with silicon compounds tended to increased seed germination. Dry matter content in the aboveground plant parts did dependent on treatment. The variety Preriya was generally characterized by higher values of this index.

Stimulation of growth in the initial period of vegetation could cause long-term effects, so it was interesting to monitor the influence of pre-sowing treatment with silicon compounds in later periods of plant development in microallotment field experiment.

The increase in plant biomass varied by years of research, and the effect of two forms of silicon compounds were distinct in years with different moisture supply (Table 2).

The variety Prairie demonstrated the greatest biomass raise promoted by seed treatment with both TES and sodium silicate under favorable moisture conditions of the year 2006. In phases of the 3rd leaf, tillering, booting, it amounted to 31,7, 28,9, 24,4 and 26,8, 19,8, 30,5 %, respectively. In the moderately dry year 2005, the biomass increase was smaller - 28.2, 20,9, 19,1 and 12,8, 16,6, 17,5%, resp.

Biomass raise in spring barley the varieties Preriya ( A) and Kamyshinsky 23 ( B) promoted by seed treatment with tetraethoxysilane (a) and sodium silicate (b) in different stages of plant growth: 1 – the 3rd leaf, 2 - tillering, 3 - booting (the average for years 2005-2007).

In the variety Kamyshinsky 23, the greatest biomass increase under the influence of silicon compounds was observed in the year 2005 - moderately dry, but with sufficient precipitation in the II half of May when barley  was tillering. In the variant with TES, the biomass increase varied from 20,4 to 24,2% of control, in the variant with sodium silicate - from 30,3 to 35,1%, resp. This fact is probably connected to specific features of Kamyshinsky 23, which has a greater potential tillering and generally better development in years with adequate moisture. Precipitation in the II half of May stimulated the better tillering, active gain of vegetative mass, and the more completely expressed positive effect of silicon. In 2006, which was more humid, but with a smaller amount of precipitation during the period of barley tillering, biomass increase from TES and sodium silicate was 15,8-21,9 and 18,4-27,8 %, respectively.

The average values of biomass raise for the years 2005-2007 in stages of the 3rd leaf, tillering and booting in variants with TES and sodium silicate were, respectively, in the variety Preriya  26,4, 23,7, 22,2 and 18,8; 15,8, 25,2%, in Kamyshinsky 23 - 19,6, 18,5, 23,5 and 23,5, 26,6, 31,7% (see Figure). In both varieties, the maximum effect from seed treatment with sodium silicate was pronounced in booting stage, which was connected with higher values of biomass gain and the faster development of treated plants compared with control.  Over the years of research, TES stimulated the total increase of plant biomass for the period from germination to booting in the variety Preriya - at 24,1% and in Kamyshinsky 23 - 20,5%, while sodium silicate - 19,9 and 27,3%, resp.

Thus, the variety Preriya demonstrated better responsiveness to seed treatment with silicon in wet year, the variety Kamyshinsky 23 - in moderately dry, but with sufficient precipitation during a tillering stage. TES effects on plant growth were similar in two studied varieties, and the action of sodium silicate was more expressed in Kamyshinsky 23. In the variety Preriya, both silicon compounds caused similar influence, while in the variety Kamyshinsky 23 was at advantage from treatment with sodium silicate.

Kamyshinsky 23 was characterized by higher content of auxins, gibberellins and cytokinins than the variety Preriya (Table 3). Treatment of seeds with silicon contributed to raise of free auxins content in the variety Kamyshinsky 23 at 40.4%, in Preriya – at 18,0%. The content of gibberellins increased only in Kamyshinsky 23 (17%), while Preriya showed the close results obtained in both control and experimental versions. In both barley varieties, no significant changes in cytokinins content were detected.

In Preria, silicon promoted the raise in content of free auxins and did not affect the content of gibberellins, probably owing to more active growth of root biomass (23.7%) compared with aboverground parts (6.9%) (see Table. 3) . In Kamyshinsky 23,  the content of both auxins and gibberellins increased due to priority in development of aboveground parts of plants, which is the location of gibberellins synthesis and the attracting center. The growth of aboveground parts was accompanied with increase in consumption of organic substances and their consequent redistribution, which ultimately shifted the ratio (biomass of aboveground organs / biomass of roots) to higher values (see Table 1).

Thus, seed treatment of spring barley with different silicon compounds has promoted a positive effect on plant growth of both studied species and affected the content of endogenous phytohormones. The variety Preriya has shown the greater responsiveness to treatment in wet year, the variety Kamyshinsky 23 - in the moderately dry, but with rainfalls in tillering stage. In Kamyshinsky 23, the silicon-stimulated growth of aboveground biomass and the simultaneous increase in content of auxins and gibberellins have been established. The similar effects of tetraethoxysilane were observed in both varieties, while sodium silicate has led to the more pronounced effect in Kamyshinsky 23. 

REFERENCES

1. A l e s h i n N.E. O biologicheskoi roli kremniya u risa. Vest. s.-kh. nauki, 1988, 10: 77-85.
2. E r m o l a e v A.A. Kremnii v sel'skom khozyaistve. M., 1992.
3. M a J.F., T a k a h a s h i E. Soil, fertilizer and plant silikon research in Japan. Amsterdam, 2002.
4. K e m e ch e v a M.Kh., S h k h a p a t s e v A.Kh. Urozhainost' semyan risa i ikh posevnye kachestva pri primenenii kremnievykh udobrenii. V sb.: Udobreniya i urozhai. Maikop, 2005: 339-344.
5. S a m s o n o v a N.E. Kremnii v pochve i rasteniyakh. Agrokhimiya, 2005, 6: 76-86.
6. B o ch a r n i k o v a E.A., M a t y ch e n k o v V.V. Kremnievye udobreniya: proshloe, nastoyashchee i budushchee. Tr. II nats. konf. «Problemy istorii, metodologii i filosofii pochvovedeniya». Pushchino, 2007, t. 2: 397-400.
7. Y o s h i d a S. The phisiology of silicon in rise. Food Fert. Tech. Centr. Tech. Bull. (Taipei, Taiwan), 1975, 4: 28-34.
8. B a r s u k o v a A.G., R o ch e v V.A. Vliyanie kremnegel'soderzhashchikh udobrenii na podvizhnost' kremnekisloty v pochvakh i dostupnost' ee rasteniyam Tr. Sverdlovskogo SKHI: Kontrol' i regulirovanie soderzhaniya makro- i mikroelementov v pochvakh i rasteniyakh na Srednem Urale, 1979, 54: 84. 
9. V o r o n k o v M.G., K u z n e t s o v I.G. Kremnii v zhivoi prirode. Novosibirsk, 1984.
10. Y a n y s h e v s k a y a O.L., Y a g o d i n B.A., D e m i n a L.Yu. Vliyanie kremniya margantsa i khroma na urozhai i nekotorye pokazateli kachestva listovogo salat. Gavrish, 2000, 2: 15-17.
11. E r m a k o v E.I. Antistressovoe vozdeistvie kremniisoderzhashchego khelatnogo mikroudobreniya na rasteniya pri nekornevoi obrabotke v zashchishchennom grunte. Gavrish, 2001, 3: 16-17.
12. S l a s t ya I.V. Kremniisoderzhashchie veshchestva kak faktor ekologizatsii zashchity rastenii, optimizatsii fitosanitarnogo statusa kul'tur i rezerv uvelicheniya proizvodstva ekologicheski bezopasnykh produktov pitaniya. Pros. of the 2PndP Int. Iran and Russia Conf. «Agriculture and Natural Resources» (February, 1-2, 2001). M., 2001: 135-139.
13. SH m a k o v a N.V. Vliyanie soedinenii kremniya i kremniifungitsidnykh smesei na fitosanitarnoe sostoyanie semyan yarovoi pshenitsy. V sb.: Adaptivnye tekhnologii v rastenievodstve. Itogi i perspektivy. Izhevsk, 2003: 159-161.
14. K e m e ch e v a M.Kh. Vliyanie predposevnoi obrabotki semyan risa kremniem na ikh posevnye kachestva. V sb.: Entuziasty agrarnoi nauki. Krasnodar, 2003, vyp. 1: 196-198. 
15. D o r o z h k i n a L.A., I v a n o v D.Yu. Primenenie silikata natriya dlya snizheniya gerbitsidnoi nagruzki v posevakh zernovykh kul'tur. Dokl. TSKHA, 2005, 277: 177-182.
16. S l a s t ya I.V. Otsenka otzyvchivosti razlichnykh sortov yachmenya na obrabotku kremniisoderzhashchimi veshchestvami. Dokl. TSKHA, 2006, 278: 676-680.
17. A l e k s e e v a V.V., R u k a v ts e v a E.B., B o b r e sh o v a M.E.,
L o z h n i k o v a V.N., B u r ' ya n o v YA.I. Poluchenie i analiz transgennykh rastenii tabaka, ekspressiruyushchikh agrobakterial'nyi gen triptofanmonooksigenazy. Fiziol. rast., 2005, 51(4): 600-606.
18. L o z h n i k o v a V.N., K h l o p e n k o v a L.P., C h a i l a k h ya n M.KH. Opredelenie prirodnykh gibberellinov v rastitel'nykh tkanyakh. V kn.: Metody opredeleniya fitogormonov, ingibitorov rosta, defoliantov i gerbitsidov. M., 1973: 50-58.
19. M o c h a c k o v a I., K o n s t a n t i n o v a T.N., S e r g e e v a L.I.,
L o z h n i k o v a V.N., G o l y a n o v s k a y a S.A., D u d k o N.D.,
E d e r J., A k s e n o v a N.P. Photoperiodic control of growth, development and phytohormone balance in Solanumtuberosum. Phisiol. Plant., 1998, 102: 272-278.