efectele radiatiilor gamma de mica intensitate asupra

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STUDIA UNIVERSITATIS BABEŞ-BOLYAI, PHYSICA, SPECIAL ISSUE, 2003

LOW INTENSITY GAMMA RADIATION

EFFECTS IN YOUNG PLANTLET ASSIMILATORY PIGMENTS

Mihaela Răcuciu

1

, Dorina Creangă

2

1

University „Lucian Blaga” of Sibiu, Faculty of Science,

Physics Department, Ion Raţiu Street, no. 7-9, e-mail: [email protected]

2

University „Al.I.Cuza” Iasy, Faculty of Physics, Bd.

Copou, no. 11

Abstract.

In this paper we studied the low intensity gamma radiation effects in young plantlets of Chelidonium majus. Experimental observation aimed: seed germination, assimilatory pigments contents, absorption and fluorescence of the photosynthesis pigments. It was observed the fluctuation of the assimilatory pigments concentrations in function on the irradiation time. We have recorded the absorption and fluorescence spectra for acetone extracts, made measurements and accomplish comparative interpretation.

Introduction

Chelidonium majus

, on the

Papaveraceae

family, was the object of many scientific researches [1] due to its rich contents in alkaloids with to its numerous therapeutic applications. Some physical factors, such as gamma irradiation, can have different effects for different radiation doses [2]. In the

Chelidonium majus

cases such effects are little knew. On this reason, we proposed to study the gamma radiation effects on the

Chelidonium majus

, through the spectrophotometry methods. We have studied the absorption and fluorescence spectra for acetone extracts.

Material and methods

The

Chelidonium majus

caryopsides have been irradiated with gamma radiation from a 10mCi Cobalt source, for different irradiation times, expressed in hours: 0,5h, 1h, 1,5h, 2h, 6h, 16,5h. After germination, from the plantlets of exposed samples and control ones, pigment extraction in 85% acetone were prepared for the spectrophotometrical assay of the assimilatory pigments contents.

We have studied the absorption spectra using the SPECORD UV-VIS spectrophotometer. After recording of the absorption spectra, we have calculated the A-chlorophyll concentration (C

Cla

), B-chlorophyll concentration (C

Clb

) and carotene pigments concentration (C ct

) (in mg of pigment/g of green tissue), according to [3] on the basis of the light extinction at the 15.080 cm

-1

, 15.500 cm

-1 and 21.190 cm

-1

. The fluorescence spectra of chlorophyll solutions (diluted in 1/10 ratio) were recorded using an adequate fluorescence installation described in [5].

For the excitation of fluorescence we have used the 23.740 cm

-1

radiation, to

MIHAELA RĂCUCIU, DORINA CREANGĂ observe the red fluorescence band and 29.720 cm

-1

radiation, to observe the blue fluorescence band.

Results and discussion

The absorption spectra for samples 1-4 are showed in Figure I. For the other samples similar spectra were recorded.

Figure I. Absorption spectra for the samples 1-4

We observed that in these spectra don’t appear evidently modifications for different samples in comparison to the control. This can be explained on the basis of the values given in Table I (the molar extinction for both chlorophyll types are concordant with [3], [7]). The values from Table I show us that the A-chlorophyll concentrations (C

Cla

) are bigger than the B-chlorophyll concentrations (C

Clb

) and carotenoid pigment concentrations (C ct

).

Table I. The concentration values to assimilatory pigments contents for control and samples

Test

1-control

2

3

4

5

6

7

Irradiation times ( h )

0

0,5

1

1,5

2

6

16,5

C

Cla

(mg/g)

0.4603

0.603

0.533

0.456

0.588

0.396

0.684

C

Clb

(mg/g)

0.046

0.127

0.066

0.04

0.107

0.063

0.064

C ct

(mg/g)

0.214

0.248

0.256

0.204

0.119

0.179

0.237

The values from Table I are presented in the graphic from Figure II.

We didn’t obtained a definite dependence of the pigment concentration on the irradiation times (or radiation dose). We observed the fluctuations of the pigment concentrations in function on the irradiation times, these fluctuations being more important in A-chlorophyll. This supposition seems to be sustained also by the fluorescence spectra. In the registered absorption spectra we observed that there is a band to about 30.000 cm

-1

(333,3 nm) which [8] is assign to the carotenoid pigments. The fluorescence spectra of the diluted acetone solution (in

LOW INTENSITY GAMMA RADIATION EFFECTS IN YOUNG PLANTLET ASSIMILATORY PIGMENTS

1/10 ratio) have two fluorescence bands: a blue range band with the maximum at

23000 cm

-1

and a red range band with the maximum at 14.600 cm

-1

.

Figure II. The fluctuations of the concentrations for different the irradiation times

The red range band is narrower than the other one. These fluorescence bands, according to [3], [7], [8] are due to A-chlorophyll and B-chlorophyll, as the carotenoid pigments don’t have significant fluorescence in these wave number ranges. In Figures III, IV, V, VI are showed absorption and fluorescence bands for control and exposed sample 2 (samples corresponding to 0,5 h – irradiation time).

We observed in these figures that fluorescence bands in the blue range is the same for the control and exposed sample, but while the fluorescence band is a smooth band, the absorption band is a structured one (Figure III and IV).

Figure III: control sample 1 Figure IV: exposed sample 2

It’s interesting that the maximum frequency for the fluorescence band in the blue range alternates in opposition with the A-chlorophyll concentration, for different irradiation times (see Figure II).

MIHAELA RĂCUCIU, DORINA CREANGĂ

Figure V: control sample 1 Figure VI: exposed sample 2

The fluorescence band in red range is very narrow so that we can’t say very much about it, but it seems to be less sensitive to the A – chlorophyll concentration fluctuations. In the red range, the fluorescence band doesn’t coincide with the absorption band for the control and exposed sample (Figure V and VI).

Conclusions

It’s possible that exposure to low activity gamma radiation source, for different irradiation times, have an influence on the plant cell nuclei inhibiting or stimulating differently the synthesis of A-chlorophyll and B-chlorophyll molecules.

This way could be explained the different modifications of these pigment concentrations in exposed samples in comparison to the control ones. These studies represent preliminary investigations regarding a larger experimental projected designed to the elucidation of the gamma radiation action in young plant cells.

References:

1.

C o l o mb o M . L . , B o s i s i o E .,

Pharmacological activities of Chelidonium majus

2.

3.

L. (Papaveraceae),

Pharmacological Research, 1996, 33(2): 127-134.

Ghior ghiţã G.I .,

Radiobiologie vegetalã

, Ed.Academiei, Bucureşti, 1987.

R a b i no wi t c h E . I .,

Spectroscopy and Fluorescence of Photosynthetic Pigments,

4.

Kinetics of Photosynthesis

, Interscince Publishers, Inc., New York, 1951.

D e R o s e V . J . , L a t i me r M . J . , Zi m me r ma n n J . , M u ke r j i I . , Y a c h a nd r a

V . K . , S a ue r K . , K l e i n M . P .,

Fluoride substitution in the Mn cluster from

Photosystem II: EPR and X-ray absorption spectroscopy studies

,

Chemical

5.

6.

7.

8.

Physics

, 1995, 194 (2-3): 443-459.

Vlaho vici A., Dr uţă I., Andrei M., C o tleţ M., Dinică R , Journal of

Luminescence, 82,155,1999.

K no x R . S .,

Excited-state equilibration and the fluorescence-absorption ratio

,

Acta Physica Polonica

, 1999, 95, 85-103.

Sălăgeanu N .,

Fotosinteza

, Ed. Academiei, 1981.

Mircea Ştirban,

Procese primare în fotosinteză

, Cluj, 1981.

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