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PRODUCTIVITY AND PHYSIOLOGICAL-RADIOCHEMICAL PECULIARITIES OF PEPPER DEPENDING ON POLYMERS APPLYING UNDER SOILLESS CULTURE

Автор Доклада: 
Tadevosyan A., Mayrapetyan S., Aleksanyan J., Ghalachyan L.
Награда: 
PRODUCTIVITY AND PHYSIOLOGICAL-RADIOCHEMICAL PECULIARITIES OF PEPPER DEPENDING ON POLYMERS APPLYING UNDER SOILLESS CULTURE

PRODUCTIVITY AND PHYSIOLOGICAL-RADIOCHEMICAL PECULIARITIES OF PEPPER DEPENDING ON POLYMERS APPLYING UNDER SOILLESS CULTURE

Tadevosyan Anna, Ph.D, Senior Researcher
Mayrapetyan Stepan, Doctor of Science, Corresponding Member of Natioanal Academy of Sciences of Armenia
Aleksanyan Julietta, Ph.D, Leading Researcher
Ghalachyan Laura, Ph.D, Senior Researcher
Institute of Hydroponics Problems the National Academy of Sciences

 

Creation of optimal conditions for plant roots, with minimal expense of water and nutrient elements, is one of the most important issues in soilless culture. Thereby the use of high-water-expending polymers in the root-inhabited media of plants can be exceptionally promising. The aim of researches is to elucidate the influence of polymers applying on the productivity and qualitative indices of pepper - Capsicum annuun L. (variety “Еlephant’s trunk”) under soilless cultivation. The studies were carried out in the open-air hydroponics conditions, in the Ararat Valley. The polymers on the base of K+, Ca++, K++Ca++ ions were tested. Productivity, physiological peculiarities of pepper depending on the presence and type of polymer material, content of artificial radionuclides (90Sr and 137Cs) in NS and plant material has been determined. The researches were implemented in the context of project A-1671 ISTC.
Keywords: hydroponics, pepper, polymer, productivity, artificial radionuclides

Introduction. Creation of optimal conditions for plant roots, with minimal expense of water and nutrient elements, is one of the most important issues in soilless culture. Thereby the use of high-water-expending polymers in the root-inhabited media of plants can be exceptionally promising. In a controlled artificial medium the closed hydroponics system allows controlled observation of the effects of polymers on growth, development, productivity and bio-radiochemical characteristics of plants. The combination of the polymer and the commercial water-soluble fertilizers notably increased tomato plants yield from 17.5% to 27.9% (4). Usage of hydrogels in nurseries effectively reduced frequency of irrigation to 4 as compared to 10 irrigations in control, to raise nursery of healthy chrysanthemum seedlings (3). Our previous researches approved effectiveness and perspective of application of hydroponical substrates with polymer (1, 9, 11). During the last years joint investigations were carried out with Yerevan Institute “Plastpolymer” (8-9). The difference of water-retention ability of polyelectrolytes with different counter ions allows one to speculate that application of water retaining polymers can influence the transport of radionuclides (RN). In practice, our preliminary studies have demonstrated that upon application of Supersorbent-87, synthesized at Yerevan Institute “Plastpolymer” RA, for plant production, there was an observed increase of 137Cs and 90Sr content in plant biomass. Amongst the man-made RN 137Cs and 90Sr exert long-term after-effects of radionuclide caused contamination: for 137Cs the half-life 30.1 years, while for 90Sr the half-life 28.6 years. The passage of RN, in particular 137Cs and 90Sr, occurs from the soil solution and irrigation water through the root system of plants (2). The aim of researches is to elucidate the influence of polymers applying on the productivity and qualitative indices of pepper - Capsicum annuun L. (variety “Еlephant’s trunk”) under soilless cultivation.

Materials and Methods. The studies were carried out in the open-air hydroponics conditions of the Ararat Valley. The outdoor hydroponic station of the Institute of Hydroponic Problems (with the radius of 30km from the Armenian Nuclear Power Plant) is situated 900 m above sea level, annual average temperature is 11.0-11.80C, relative humidity is 40%, annual average sum of precipitation is 200-300 mm, heating degree days are 2300-2700. Pepper seedlings were planted in hydroponics equipment (2m x 1m x 0.25m) with 2m2 growing space (20plant/m2). In the experiments mixture of gravel and volcanic slag (1:1) with 2-10mm diameter of pieces was used as substrate and the plants were nourished with Davtyan’s nutrient solution (NS), N200P65K300, pH 5,5-6,5 (5) using closed ebb flow watering system.

Different high-water-expending polymers (on the base of K+, Ca++, K++Ca++ ions), synthesized in the “Plastpolymer” Institute were tested.

The experiments were carried out with the following variants:

  • 1. Control-substrate without polymer, nourishment frequency (NF) twice a day;
  • 2. Substrate + polymer K(1g/plant), NF once a day;
  • 3. Substrate + polymer Ca++ (1g/plant), NF once a day;
  • 4. Substrate + polymer K+ + Ca++ (1g/plant), NF once a day.

Biometric measurements and physiological, biochemical and radiochemical analysis of pepper different organs (fruits, leaves+stems, roots) were made during the investigations. The parameters of water regime in leaves determined by Gusev (7),content of vitamin C in pepper fruits by titration method (6), content of RN by radiochemical methods by means of UMF-1500 device (10). The data were analysed by Graph Pad Prism 5Demo.

Results and Discussion. The indices of pepper productivity grown under hydroponics condition were shown in the Table 1.

Considerable differences were observed only between control and K+ variants: pepper yield, leaves+stems and roots weight in control variant exceeded K+ variant 1.7, 1.5 and 1.6 times, accordingly. From polymer variants Ca++ variant was observed which exceeded other polymer variants by pepper yield, leaves+stems and roots weight 1.7 – 1.8, 1.2 – 1.5 and 1.2 – 1.3 times, accordingly. In Ca++ variant, the amount of pepper increased 1.4 times, and the weight of a single pepper exceeded the other polymer variants 1.2 – 1.3 times.

Table 1. Indices of pepper productivity under soilless culture depend on the use of polymer

Variants

Fresh mass ofpeppers, g/plant

Amount of peppers, piece/plant

Fresh mass

of onepepper, g

Fresh mass ofleaves+stems,g/plant

Fresh mass of roots,g/plant

Control-

without polymer

976a

63

15.5

264

34.2

Substrate +

polymer K+

578b

43

13.4

179

21.4

Substrate +

polymer Ca++

1064ac

61

17,4

272

27.2

Substrate +

polymer K++Ca++

627ab

44

14.2

227

23.2

abc Tukey's Multiple Comparison Test (P<0.05)

There are no considerable differences among the indices of plant productivity in the best polymer (Ca++) and control variants. In these variants, yields formed about 80% in the above-ground mass of plants (Fig. 1).

In fact, we can record that in case of double reduction of nourishment regime Ca++polymer provide a crop equal the control variant.

Percent of fruits and leaves+ stems in the above-ground biomass of pepper

Fig. 1. Percent of fruits and leaves+ stems in the above-ground biomass of pepper
1. Control-without polymer; 2. Substrate + polymer K+; 3. Substrate + polymer Ca++
4. Substrate + polymer K++Ca++

Physiology-biochemical studies have shown (Table 2 and Fig. 2) that the use of polymers in the case of double decrease of NF promotes the increase of water-holding capacity in plant tissues: in this case, in comparison of control variant, the decrease of free water about 1.1-1.4 times in pepper leaves and at the same time the increase of bound water with the 12-47% was registered. It resulted in an increase of the values of cellular fluid osmotic pressure about 6-28%.

Vitamin C content in pepper fruits was influenced by use of the polymer when compared to the control. An increase in vitamin C content by 23-45% was observed in the polymer variants (Table 2).

 Influence of polymer on the total water content in pepper leaves under hydroponics conditions (July)

Fig. 2. Influence of polymer on the total water content in pepper leaves under hydroponics conditions (July)

Table 2. Influence of polymer in the substrate on the physiological-biochemical indices of pepper under hydroponics conditions (July)

Indices

Variants

Control

Substrate+ polymer K+

Substrate+ polymer Ca++

Substrate+ polymer K++ Ca++

Free and bound water ratio

2.2

1.1

1.7

1.8

Osmotic pressure of cellular fluid, atm.

6.13

7.83

6.61

6.51

Colloid bound water, %

10.1

19.6

14.8

13.1

Osmotic bound water, %

15.9

18.6

16.4

16.0

Vitamin C, mg%

105.2

152.8

129.4

132.5

The content of RN in artesian water, starting NS and NS after 5 days using for pepper was investigated.

The results of experiments have shown (Table 3) that the starting NS exceeds the artesian water (on the base of which the NS was prepared) with the content of 90Sr (2.5 times) and 137Cs (3.0 times). It means that the RN were transferred in NS from artesian water and nutrient salts, which are used for preparation of NS. When the starting NS contacted with the plants roots and substrates 10 times (2 times a day) in the control and5 times (once a days) in the polymers containing variants established a fact of increase of NS concentration because of water loss due to evaporation from NS. In the control variant the dry residue in the NS increased 1.4 times after 5 days of using and in the polymer variants – 1.5-1.8 times. The high air temperature promoted it. As a result, in the 5th day of using the content of 90Sr increased in the NS 2.0 times. But 137Cs content remained unchangeable besides K+ Ca++ variant.

Table 3. Radioactivity of artesian water and NS

Sample

Dry residue, g/L

Bq/L

90Sr

137Cs

Artesian water

0.6

0.04

0.01

Starting NS

1.0

0.10

0.03

Used NS (after 5 days)

Control

Substrate K+

Substrate Ca++

Substrate K+ Ca++

 

1.4

1.5

1.8

1.6

 

0.20

0.20

0.20

0.20

 

0.03

0.03

0.03

0.04

Though in starting NS 90Sr content 3.3 times and during 5 days after being in touch with plant roots and substrate 6.6 times exceeded 137Cs (Table 3), but in pepper organs on the contrary 137Cs content exceeded 90Sr, in addition, more - in polymer variants (Table 4). So 137Cs content exceeded 90Sr in pepper fruit of control variant 4.4 and in polymer variants 4.6-7.2 times, in leaf+stem of control variant - 1.9 and in polymer variants - 2.4-2.9 times, in roots of control variant - 3.5 and in polymer variants - 9.4-11.9 times. The results showed that the most exceeding of 137Cs content to 90Sr was observed in pepper roots, the least - in leaf+stem. Pepper organs according to 90Sr content have the following trend: leaf+stem>fruit>root, and according to 137Cs content: leaf+stem>root>fruit.

Table 4. Content of artificial RN in different organs of hydroponics pepper, Bq/kg

Organs

Variants

90Sr

137Cs

Fruits

control-without polymer

1.7±0.2

7.5±0.1

substrate + polymer K+

1.6±0.25

11.3±0.15

substrate + polymer Ca++

1.2±0.21

8.6±0.2

substrate + polymer K++Ca++

2.3±0.1

10.5±0.1

 

Leaves+stems

 

control-without polymer

8.9±0.35

16.7±0.2

substrate + polymer K+

7.7±0.69

18.9±0.1

substrate + polymer Ca++

6.7±0.89

19.4±0.2

substrate + polymer K++Ca++

7.8±0,42

22.1±0.15

Roots

control-without polymer

1.5±0.2

5.2±0.15

substrate + polymer K+

1.1±0.02

10.3±0.2

substrate + polymer Ca++

0.9±0.09

10.7±0.1

substrate + polymer K++Ca++

1.5±0.19

14.5±0.35

MACL (12)

 

20

60

The data showed that 90Sr content in pepper fruit in Ca++ polymer variant concedes the control variant 1.4 times, K++ Ca++ polymer variant 1.9 times, and it does not differ significantly from the same indices of Kpolymer. 137Cs content in pepper fruit in Ca++polymer variant conceded K+ and K++ Ca++ polymer variants 1.3 and 1.2 times, accordingly but exceeded control variant about 15%.

There is a directly proportional coupling between 90Sr and 137Cs content in different organs of pepper: r = 0.84 ± 0.17.

It has been confirmed that the content of controlled artificial RN 90Sr and 137Cs in the fruits of pepper in all variants is much smaller than the Maximum Allowed Concentration Limits (MACL).

Conclusion.

  1. In case of using Ca++ polymer in root-inhabited media the same yield of pepper fruit is provided by reducing the expenses of water and nutrient salts twice.
  2. Use of the polymer increases Vitamin C content in pepper fruits by 23-45% compared to the control.
  3. 137Cs content exceeded 90Sr in different organs of pepper grown under hydroponics condition especially in polymer variants.
  4. The presence of Ca++ polymer in substrate promoted the decrease of 90Sr content in pepper fruit in comparison of control variant 1.4 times.
  5. The researches were implemented in the context of project A-1671 ISTC.

References:

  1. Alexsanyan J.S. and Mairapetyan S.Kh. 1992. Strongly swelling polymer hydrogel as additional component of hydroponic substrates / Proc. 8th Intern. Congress on Soilless Culture, Hunters Rest, South Africa 2-9 October, p. 4.
  2. Alexakhin R. M., Buldakov L.A., Gubanov V.A., et al. Large radiation accidents. Consequences and protective countermeasures. M.: IzdAt, 2001, 752 P.
  3. Anupama Singh M.C., Kumar R., Parmar B.S. and Kumar A. 2007. Performance of a new superabsorbent polymer on seedling and post planting growth and water use pattern of chrysanthemum grown under controlled environment / Acta Hort. 742:43-49.
  4. Chatzoudis G.K. and Rigas F.P. 2003. Combined action of hydrogel and controlled-release fertilizers on growth of tomato plants / Acta Hort. 613:193-196.
  5. Davtyan G.S. 1980. Hydroponics. p. 382-385. In: The reference book on the chemicalization of agriculture. Moscow. Kolos.
  6. Ermakov A.I., Arasimovich V.V., Smirnova-Ikonikova M.I., Murri I.K. The biochemical experimental method of plants, Moscow: 1952, p. 89.
  7. Gusev N.A. 1989. Study methods of water exchange of plants. Kazan, Publishing House of the Kazan University, п. 17-19.
  8. Hovsepyan A.H., Eloyan S.A., Poghosyan G.Y., Mairapetyan S.Kh., Voskanyan P.S. 2007. The Eastern Oaks Hydroponic Saplings’ Testing in Dilijan Biogeocenose Conditions/ “Communications” of IHP NAS RA, #31, p 69-73.
  9. Mairapetyan S.Kh., Tadevosyan A.H., Alexanyan J.S., Galstyan H.M., Stepanyan B.T., Tovmasyan A.H., Khechoyan S.A., Tavakalyan N.B., Voskanyan P.S. 2008.Effectiveness of Polymers in Hydroponic Cultivation / Practical Hydroponics and Greenhouses, Australia, # 100, p. 47-50.
  10. Pavlotskaya F. I. 1974. Migration of radioactive products of global fall-out in soils, Moscow: 257P.
  11. Pogosyan G.M., Karapetyan T.K., Shakaryan V.M., Alexsanyan J.S. and Mairapetyan S.Kh. 1998. Тhe synthesis of polymer compounds on the basis of acryl monomers and their application in hydroponics / Applied Chemical Journal of Armenia, N1, p. 35-38.
  12. The Radiation Safety Norms. 1999. Hygienic Norms. Moscow, Sanitary Rules and Regulations Centre, Ministry of Public Health of Russia, 116P.
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