VYTAUTAS MAGNUS UNIVERSITY
LITHUANIAN FOREST RESEARCH INSTITUTE
Kristina Dėdelienė
SINGLE AND INTEGRATED IMPACT OF OZONE
AND UV-B RADIATION ON SPRING BARLEY
(Hordeum vulgare L.)
Summary of Doctoral Dissertation
Biomedical Sciences, Ecology and Environmental Sciences (03 B)
Kaunas, 2007
The right of doctoral studies was granted to Vytautas Magnus University jointly with
Lithuanian Forest Research Institute on July 15, 2003, by the decision No. 926 of the
Government of the Republic of Lithuania.
Dissertation was performed at Vytautas Magnus University in 2003-2007.
Scientific Supervisor:
prof. habil. dr. Romualdas Juknys (Vytautas Magnus University, Biomedical Sciences,
Ecology and Environmental Sciences 03 B).
Council of defence of the doctoral dissertation:
Chairman:
prof. habil. dr. Vida Stravinskienė (Vytautas Magnus University, Biomedical Sciences,
Ecology and Environmental Sciences 03 B).
Members:
doc. dr. Natalija Burbulis (Lithuanian University of Agriculture, Biomedical Sciences,
Agronomy 06 B);
prof. habil. dr. Remigijus Ozolinčius (Lithuanian Forest Research Institute, Biomedical
Sciences, Ecology and Environmental Sciences 03 B);
dr. Vida Rančelienė (Institute of Botany, Biomedical Sciences, Botany 04 B);
doc. dr. Jonė Venclovienė (Vytautas Magnus University, Biomedical Sciences,
Ecology and Environmental Sciences 03 B).
Oponents:
dr. Danguolė Raklevičienė (Institute of Botany, Biomedical Sciences, Botany 04 B);
dr. Vidas Stakėnas (Lithuanian Forest Research Institute, Biomedical Sciences,
Ecology and Environmental Sciences 03 B).
The official defence of the dissertation will be held at 2 p.m. on November 30, 2007 at a
public meeting in the 605 hall at Vileikos st. 8.
Address: Vileikos st. 8, LT-44404, Kaunas, Lithuania
Phone: (+37037327904)
Summary of doctoral dissertation was sent out on October
2007.
The dissertation is available at M. Mažvydas National Library of Lithuania and the
libraries of Vytautas Magnus University and Lithuanian Forest Research Institute.
2
VYTAUTO DIDŽIOJO UNIVERSITETAS
LIETUVOS MIŠKŲ INSTITUTAS
Kristina Dėdelienė
PRIEŽEMIO OZONO IR UV-B SPINDULIUOTĖS
DIFERENCIJUOTAS IR KOMPLEKSINIS
POVEIKIS VASARINIAMS MIEŽIAMS
(Hordeum vulgare L.)
Daktaro disertacijos santrauka
Biomedicinos mokslai, ekologija ir aplinkotyra (03 B)
Kaunas, 2007
3
Doktorantūros ir daktaro mokslų laipsnių teikimo teisė suteikta Vytauto Didžiojo
universitetui kartu su Lietuvos miškų institutu 2003 m. liepos mėn. 15 d. Lietuvos
Respublikos Vyriausybės nutarimu Nr. 926.
Disertacija rengta 2003-2007 metais Vytauto Didžiojo universitete.
Mokslinis vadovas:
prof. habil. dr. Romualdas Juknys (Vytauto Didžiojo universitetas, biomedicinos
mokslai, ekologija ir aplinkotyra 03 B)
Disertacijos gynimo taryba:
Pirmininkė:
prof. habil. dr. Vida Stravinskienė (Vytauto Didžiojo universitetas, biomedicinos
mokslai, ekologija ir aplinkotyra 03 B).
Nariai:
doc. dr. Natalija Burbulis (Lietuvos žemės ūkio universitetas, biomedicinos mokslai,
agronomija 06 B);
prof. habil. dr. Remigijus Ozolinčius (Lietuvos miškų institutas, biomedicinos mokslai,
ekologija ir aplinkotyra 03 B);
dr. Vida Rančelienė (Botanikos institutas, biomedicinos mokslai, botanika 04 B);
doc. dr. Jonė Venclovienė (Vytauto Didžiojo universitetas, biomedicinos mokslai,
ekologija ir aplinkotyra 03 B).
Oponentai
dr. Danguolė Raklevičienė (Botanikos institutas, biomedicinos mokslai, botanika 04
B);
dr. Vidas Stakėnas (Lietuvos miškų institutas, biomedicinos mokslai, ekologija ir
aplinkotyra 03 B).
Disertacija bus ginama viešame Ekologijos ir aplinkotyros mokslo krypties tarybos
posėdyje 2007 m. lapkričio 30 d. 14 val. Vytauto Didžiojo universiteto II rūmuose,
Vinco Čepinskio tiksliųjų mokslų skaitykloje, Vileikos g. 8-605.
Adresas: Vileikos g. 8, LT-44404, Kaunas,
tel. (faksas) +370 37 327904.
Disertacijos santrauka išsiųsta 2007 m. spalio mėn.
d.
Su disertacija galima susipažinti Lietuvos nacionalinėje M. Mažvydo bibliotekoje ir
Vytauto Didžiojo universiteto bei Lietuvos Miškų instituto bibliotekose.
4
Introduction
Ever more urgent have become environmental problems related to changes in
the concentrations of ozone in the stratosphere and troposphere. Since the beginning of
1980s a quite rapid depletion of the stratospheric ozone layer and the increase of the
ultraviolet radiation intensity have been observed (Krizek et al., 1998). Based on the
data of different institutions, the stratospheric ozone layer since the beginning of 1980s
has significantly depleted, and in 1997-2001 average ozone layer in the world was by 3
% thinner than in 1980 (WMO, 2003). Ozone layer in Europe over the same period has
depleted by about 7 % (EEA, 2003).
The stratospheric ozone layer protects life on the Earth from the sun's harmful
ultraviolet (UV) rays. Reductions in atmospheric ozone are expected to result in higher
amounts of ultraviolet-B (UV-B) radiation reaching the Earth's surface (Cicerone,
1987).
Another problem related to ozone is increasing tropospheric ozone level. Solar
UV drives photolysis of NO2, as a main precursor of ozone, and leads to the production
of O3 in the troposphere (Thompson et al., 1991; Wayne, 2000).
During more than 20 years of monitoring an obvious annual increase of the
mean ground level ozone concentrations has been observed: 0.9 µg m-3 (Girgždienė,
Girgždys, 2003). The diurnal mean ozone concentrations for the growing season are
rather often higher as compared with the target value of 65 µg m-3. Concentrations of
the surface ozone also exceeded the levels affecting human health.
Mean daily value of UV-B radiation in Lithuania on sunny days may comprise
2,5 kJ m-2 d-1 (Chadyšienė et al., 2005), while in other latitudes the intensity of UV-B
radiation increase up to 11 kJ m-2 d-1 (Frederick et al., 2000).
Studies conducted by different authors show that the impact of UV-B on plants
is versatile. UV-B radiation causes a reduction in plant height, fresh and dry biomass,
amounts of chlorophylls and carotenoids (Ambasht, Agrawal, 1997, 1998; Correia et al.,
1999a; Mazza et al., 1999; Nasser, 2001). Studies have shown that UV-B radiation
significantly affected the growth parameters of barley plants, such as plant length, tiller
number, leaf area, fresh and dry weight of plants (Nasser, 2001). Crepis capillaris
plants were irradiated by UV-B doses in the range of 0-9 kJ m-2d-1. A significant effect
on plant growth (expressed in fresh and dry plant weight, leaf area), superoxide
dismutase (SOD) activity and protein content in the leaves was exerted by irradiation
with even the lowest (1 kJ m-2 d-1) UV-B dose (Rančelienė et al., 2005).
Ozone experiments with trees and plants have shown that elevated tropospheric
ozone concentrations induced external lesion of plants, had a negative impact on growth
and photosynthetic apparatus (Skärby, 1994; Küppers et al., 1994; Miller et al., 1994;
Fiscus et al.,1994; Fiscus and Booker, 1995). Ozone, as one of the most powerful agents
of oxidative stress, forms free radicals and may result in a wide range of physiological
changes, such as alteration of membranes, reduction in the amount and activity of
Rubisco, acceleration of leaf senescence (Ludwikow et al., 2004).
Normally, under natural conditions, organisms and ecosystems are subjected to
the influence of many different stress factors. Increasing levels of ozone and UV-B
radiation have negative impact on plant vegetation, cause morphological and
physiological alterations of all plant organisms (Runeckles and Krupa, 1994; Caldwell
et al., 1995). However, there data showing that even a small amount of UV-B radiation
5
may have an adverse effect on the stress tolerance of plants. For instance, data indicate
that UV-B radiation, applied together with O3, ameliorates the detrimental effects of O3
(Schnitzler et al., 1999).
Adaptation possibilities of plants to environmental and climatic changes are
becoming as a one of the most topical scientific issues and have an indubitable
practical value. The increase of tropospheric ozone concentration and UV-B radiation in
nature has lead to the investigations of the vegetation of spring barley plants under
controlled environmental conditions. Despite a large number of studies on the single
effect of UV-B radiation and ozone on plant organism, an integrated impact of the
present factors and possibilities of cross adaptation has been investigated on a relatively
rare.
In Lithuania such investigations have been carried out since 2003, as a part of
the project “Integrated impact of anthropogenic climatic and environmental changes to
the vegetation of forest and agro-ecosystems”, financed by the Lithuanian State Science
and Studies Foundation.
Objective of the research
The objective of this research was to investigate the impact of tropospheric
ozone and UV-B radiation on spring barley (Hordeum vulgare L.) and adaptation
possibilities of barley to single and integrated impact of these factors.
The research was based on the following hypothesis: spring barley plants
adapted to one stressor have higher capacity for physiological acclimation not only to
the same factor, but also acquires resistance to other negative environmental factors.
Main tasks of the research:
1. To determine the limits of spring barley tolerance to the impact of UV-B
radiation.
2. To determine the limits of spring barley tolerance to the impact of ozone.
3. To investigate the response of different barley cultivars to elevated UV-B
radiation.
4. To investigate the response of different barley cultivars to elevated
tropospheric ozone concentration.
5. To estimate the effect of UV-B radiation on spring barley under different
amount of photosynthetically active radiation (PAR).
6. To investigate single and integrated impact of tropospheric ozone and UV-B
radiation on spring barley plants and barley adaptation possibilities to the
impact of these factors.
Scientific novelty
It was first time in Lithuania investigated the impact of elevated ozone and
UV-B radiation on different cultivars of spring barley.
Adaptation possibilities to single and integrated impact of ozone and UV-B
radiation on spring barley were investigated and the limits of barley tolerance to these
factors were established.
6
Materials and methods
Spring barley (Hordeum vulgare L.), as one of the most widely grown cereal
crops in Lithuania, has been chosen as the object of this study.
Experiments were carried out in growth chambers of controlled environment at
Vytautas Magnus University (VMU) and in the Lithuanian Institute of Horticulture
(LIH) during 2003-2007, as a part of the national scientific project “Integrated impact of
anthropogenic climatic and environmental changes to the vegetation of forest and agroecosystems”.
Fig. 1. Spring barley in phytotron chambers of controlled environment at Vytautas
Magnus University (VMU) and in the Lithuanian Institute of Horticulture (LIH)
Plants were sown and grown in peat substrate (pH 6,0-6,5). A photoperiod of 16
h was used and air temperature of 21/17oC (day/night) was maintained in phytotron
chambers throughout the experiment. The impact of tropospheric ozone and UV-B
radiation on plants were investigated. Ozone concentration was generated using ozone
generator OSR-8 (Ozone Solutions, Inc.). UV-B radiation was generated using UV-B
lamps (TL 40W/12 RS UV-B Medical, Philips). The UV-B doses were measured with a
VLX-3 radiometer (Vilber-Lourmat, France).
The concentration of carotenoids and chlorophylls a and b was determined in
100 % acetone by the method of D.Wettstein with a spectrophotometer at 662, 644 and
440.5 nm for chlorophyll a, chlorophyll b and carotenoids, respectively (Brazaitytė,
1998). Glutathione concentration was extract by the method of J.V.Gronwald et al.
(1987).
25 barley plants were sown and grown in 3 l pots in VMU and in 5 l pots in LIH.
Each investigated variant was repeated three times.
Impact of ultraviolet (UV-B) radiation on the morphological and
physiological indices of spring barley
In order to determine the limits of tolerance to ultraviolet-B radiation, the effect
of different UV-B doses on morphological and physiological indices of spring barley
were investigated. Investigations were carried out at the phytotron complex of the
Lithuanian Institute of Horticulture. Spring barley cultivar ‘Aura’ was chosen as the
object. Plants were exposed to 0 (reference treatment), 1, 3, 5, 7 and 9 kJ m-2 d-1 UV-B
radiation doses for five days.
7
Impact of ozone (O3) to the morphological and physiological indices of
spring barley
The impact of ozone on spring barley was investigated in the phytotron complex
of the Lithuanian Institute of Horticulture. The cultivar of spring barley ‘Aura’ was
analysed. Different ozone concentrations were maintained as follows: 0 (reference
treatment), 120, 240 and 360 g m-3. Plants were treated with the following ozone
concentrations 7 h per day, 5 days per week.
Impact of elevated UV-B radiation on different spring barley cultivars
Seven cultivars of spring barley: ‘Aura’, ‘Annabell’, ‘Henni’, ‘Tolar’, ‘Jersey’,
‘Scarlet’ and ‘Barke’ were grown under controlled conditions in the growth chambers at
the Vytautas Magnus University. After seven days of growth plants were divided in to
two halves. One half of each cultivar of barley plants was irradiated with 8 kJ m-2 d-1
UV-B radiation. The other part of barley was grown in the reference treatment chamber
(zero UV-B radiation).
Impact of elevated ozone on different spring barley cultivars
Seven cultivars of spring barley (‘Aura’, ‘Annabell’, ‘Henni’, ‘Tolar’, ‘Jersey’,
‘Scarlet’ and ‘Barke’) were grown in the phytotron complex of the Lithuanian Institute
of Horticulture. After seven days of growth the plants were divided in to two halves.
One half of each cultivar of barley plants was exposed to 240 g m-3 ozone
concentration. Plants were exposed for five days, 7 h per day. The other part of barley
was grown in the reference treatment chamber where ozone concentration was 0 g m-3.
The effect of UV-B radiation on spring barley under different amount of
photosynthetically active radiation (PAR)
Spring barley plants were grown in different growth chambers in different
places: Lithuanian Institute of Horticulture and Vytautas Magnus University.
For the first experiment plants were grown in a greenhouse of the Lithuanian
Institute of Horticulture (LIH), prior to being transfered to the growth chamber. In the
greenhouse plants received a natural amount of photosynthetically active radiation
(PAR). For the second experiment, the plants were grown in chambers at Vytautas
Magnus University (VMU) all the time and received a relatively small amount of PAR.
Spring barley cultivar ‘Aura’ was chosen as the object.
In LIH plants were grown in the greenhouse for eleven days after sowing, with
illumination of 20 000 lux. Then plants were transfered to the phytotron chamber. After
transfer, the plants were acclimated for two days before being exposed to UV-B
radiation. Plants were exposed for five days to 0 (control), 1, 3, 5, 7 and 9 kJ m-2 d-1
UV-B radiation.
In VMU, during all the time of experiment plants were grown in a growth
chamber, with illumination of 5 000 lux. After six days plants were exposed to 0
(reference treatment), 1, 2, 3, 4, 6, 8 and 10 kJ m-2 d-1 UV-B radiation. The duration of
exposure was five days.
8
Single and integrated impact of tropospheric ozone and UV-B radiation on
spring barley plants and barley adaptation possibilities to the single and integrated
impact of these factors
Single and integrated impact of tropospheric ozone and UV-B radiation on
spring barley (Hordeum sativum L.) plants has been investigated in the phytotron
complex of the Lithuanian Institute of Horticulture. Spring barley cultivar ‘Aura’ was
chosen as the object of this investigation.
Plants for nine days after sowing were grown in a greenhouse. Then plants were
transfered to phytotron chambers. There were two stages of experiment. During the first
(adaptation) stage barley seedlings were adapted for five days to a relatively low UV-B
radiation (3 kJ m-2 d-1) or to a relatively low concentration of ozone (120 g m-3).
Other part of plants was grown without exposure to UV-B or ozone (reference
treatment) (Fig. 2).
In the second (main impact) stage, investigated plants for five days were
exposed to 9 kJ m-2 d-1 UV-B dose or to 360 g m-3 ozone. Untreated plants were also
exposed to a higher UV-B dose or higher ozone concentration. Besides, three vegetative
pods during all the time of experiment were grown in the control chamber (absolute
control).
Adaptation impact
UV-B – 3 kJ m-2 d-1
UV-B
UV-B
UV-B
UV-B
Reference
R
Main impact
UV-B – 9 kJ m-2 d-1
R
UV-B
R
O3
O3
O3
O3
O3
Adaptation impact
O3 – 120 µg m-3
Main impact
O3 – 360 µg m-3
Fig. 2. Scheme of single and integrated impact of ozone and ultraviolet (UV-B)
radiation
A photoperiod of 16 h was used and air temperature of 21/17oC (day/night) was
maintained in phytotron chambers throughout the experiment. The experiment lasted for
23 days.
Statistical data analysis
The results were statitically analysed with the analysis of variance in a twofactor method and regresion analysis. The t-test and Mann-Whitney U test were applied
for the evaluation of the significance of differences at the confidence level p0.05. The
data were analysed by STATISTICA statistical program.
9
Results and discussion
Impact of ultraviolet (UV-B) radiation on the morphological and
physiological indices of spring barley
Plant height, cm nnn
In order to determine the limits of tolerance to UV-B radiation, the impact of
different UV-B doses on the growth of spring barley were investigated. Plants were
exposed to 0 (reference treatment), 1, 3, 5, 7 and 9 kJ m-2 d-1 UV-B radiation doses.
Data relating to the impact of UV-B radiation on the growth of spring barley are
presented in Figure 3. UV-B radiation caused a significant reduction in plant height
(p0.05), in comparison with the reference treatment. It was determined that even
1 kJ m-2 d-1 UV-B radiation has reduced plant height of spring barley by 3 %. UV-B
radiation dose of 5 kJ m-2 d-1 has diminished plant height – by 4 %, 7 kJ m-2 d-1 – by
10 % and 9 kJ m-2 d-1 – by 6 %.
41
40
39
38
37
36
35
34
0
1
3
5
-2
7
9
-1
kJ m d
Fig. 3. The impact of different UV-B doses: 0, 1, 3, 5, 7 and 9 kJ m-2 d-1 on the height of
spring barley plants
UV-B caused decrease in fresh and dry weight of the aboveground part of barley
(Fig. 4). Fresh and dry weight of plants decreased with increasing UV-B dose. Fresh
weight under 1 kJ m-2 d-1 UV-B radiation decreased by 22 %, and the difference from
the reference treatment was statistically significant (p0.05). UV-B radiation dose
of 3 kJ m-2 d-1 has diminished fresh weight of plants by 33 %. It was found that UV-B
radiation dose of 7 kJ m-2 d-1 even by 43 % reduced biomass accumulation. Plant
biomass decreased by 38 % when treated with 9 kJ m-2 d-1 UV-B radiation dose, as
compared to the reference treatment
Dry weight of spring barley has significantly decreased even after UV-B
irradiation with the lowest 1 kJ m-2 d-1 dose (p0.05). Plants dry weight decreased by
34 %, treated with 9 kJ m-2 d-1 UV-B radiation dose.
10
220
±1.96*Std. Err.
±1.00*Std. Err.
Mean
1700
1500
1300
1100
Dry weight, mg
Fresh weight, mg
1900
±1.96*Std. Err.
±1.00*Std. Err.
Mean
200
180
160
140
120
100
900
0
1
3
5
7
0
9
1
3
5
7
9
kJ m-2 d-1
kJ m-2 d-1
Fig. 4. Impact of different UV-B doses: 0, 1, 3, 5, 7 and 9 kJ m-2 d-1 on fresh and dry
weight of the aboveground part of spring barley plants
mg g
-1
Data related to the impact of UV-B radiation on the content of photosyntetic
pigments of spring barley are presented in Figure 5. The content of a and b chlorophyll
in the leaves of spring barley decreased with increasing UV-B dose. Plants treated
with 1 kJ m-2 d-1 UV-B had by 7 % less chlorophyll a and even by 15 % less
chlorophyll b, but this reduction was not significant, as compared to the reference
treatment. A significant reduction in the content of chlorophyll a and b was detected
under 3 kJ m-2 d-1 UV-B radiation dose (p0.05). In this dose variant, the content of
chlorophyll a and b in barley leaves decreased by 26.5 % and 27.5 %, respectively.
After irradiation with 5 kJ m-2 d-1 UV-B dose, chlorophyll a content decreased by
30.5 %, chlorophyll b – by 45 %. In the highest investigated UV-B dose variant
(9 kJ m-2 d-1) chlorophyll a content decreased even by 50 %, chlorophyll b – by 48 %.
No significant differences were observed in chlorophyll a/b ratio in the leaves of spring
barley exposed to different UV-B doses.
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0.4
0.3
0.2
0.1
0.0
1
3
5
7
9
2.5
0
c
2.0
-1
b
0.5
0
mg g
0.6
a
1
3
5
7
9
4.0
d
3.0
1.5
2.0
1.0
1.0
0.5
0.0
0.0
0
1
3
5
kJ m-2 d -1
7
9
0
1
3
5
7
9
-2 -1
kJm d
Fig. 5. Impact of different UV-B doses: 0, 1, 3, 5, 7 and 9 kJ m-2 d-1 on the content of
photosynthetic pigments: a – chlorophyll a, b – chlorophyll b, c – total chlorophyll a
and b content, d – chlorophyll a/b ratio in leaves of spring barley plants
11
Glutathione concentration mg g
-1
A decrease in photosynthetic pigments during exposure to UV-B radiation is in
agreement with the previous studies (Li et al., 2000a; Alexieva et al., 2001; Zu et al.,
2003). However, our results are contrasting with the data of N.K. Ambasht, M. Agrawal
(1995) and C.M. Correia et al. (1999b). Their results suggest that chlorophyll content in
the leaves of investigated plants increased under exposure to UV-B radiation.
Biochemical analysis has shown that UV-B radiation causes the increase of the
total glutathione concentration in the tissues of barley leaves by more than three times
(Fig. 6).
180
160
140
oxidized
total
120
100
80
60
40
20
0
Reference
UV-B
Fig. 6. Impact of UV-B radiation on the glutathione concentration in the tissues of
spring barley leaves
The impact of UV-B radiation reduced also the ratio of reduced and oxidized
glutathione. The leaves of the reference treatment plants contained 49.7 % of reduced
glutathione from the total amount, meanwhile, in the leaves affected by UV-B radiation
it decreased down to 35.4 %.
Increases in glutathione concentration suggest that in plants are activated
adaptation processes. However decrease of reduced glutathione means that it is used for
neutralization of reactive oxygen species.
Impact of ozone (O3) on the morphological and physiological indices of
spring barley
The impact of ozone on spring barley was investigated in the phytotron complex
of the Lithuanian Institute of Horticulture. Ten days’ plants were exposed to 0
(reference treatment), 120, 240 and 360 g m-3 of ozone for five days per week, 7 h per
day.
The impact of ozone caused visible leaf injury and accelerated senescence of
spring barley leaves. Data regarding the impact of ozone on the growth of spring barley
are presented in Figure 7. No regular changes in plant height were observed. After
exposure to 240 g m-3 ozone concentration, the height of plants had even an
12
Plant height, cm mm
insignificant increase (5 %). Ozone stimulated genesis of new leaves.
52
50
48
46
44
42
0
120
240
360
g m-3
Fig. 7. Impact of different ozone concentrations (0, 120, 240 and 360 g m-3) on the
height of spring barley plants
Fresh and dry weight had a tendency to decrease with increasing ozone
concentrations (Fig. 8). The results have shown that 120 g m-3 ozone concentration
has decreased fresh weight by 17 %, 240 g m-3 ozone concentration – by 24 % and
360 g m-3 ozone concentration – 32 %. Dry weight of spring barley decreased with
increasing ozone concentrations no so essentially. Exposure to 240 g m-3 ozone
concentration decreased dry weight of plants by 8 %, 360 g m-3 ozone concentration –
by 12 %. At the lowest ozone concentration dry weight was by 6 % higher in
comparison to reference treatment, however difference was statistically insignificant
(p>0.05).
±1.96*Std. Err.
±1.00*Std. Err.
Mean
Fresh weight, mg
2000
1800
1600
1400
1200
1000
800
330
290
270
250
230
210
0
120
g m-3
240
360
±1.96*Std. Err.
±1.00*Std. Err.
mean
310
Dry weight, mg
2200
0
120
240
360
g m-3
Fig. 8. Impact of different ozone concentrations (0, 120, 240 and 360 g m-3) on fresh
and dry weight of spring barley plants
It was determined that ozone negatively influenced chlorophyll a content and
chlorophyll b content in the leaves of spring barley (Fig. 9). After exposure to
120 g m-3 ozone concentration, chlorophyll a content decreased by 12 %, 240 g m-3
ozone concentration – by 17 %, 360 g m-3 ozone concentration – by 35 %. After
exposure to 120 g m-3 ozone concentration chlorophyll b content decreased by 17 %,
13
240 g m-3 ozone concentration – by 14 % and 360 g m-3 ozone concentration – by
35 %. These differences from reference treatment were statistically significant
(p0.05) only at 360 g m-3 ozone concentration. The ratio of chlorophyll a and b
remained unchanged.
mg g
-1
1.4
a
0.30
1.0
0.25
0.8
0.20
0.6
0.15
0.4
0.10
0.2
0.05
0.0
-1
b
0.00
0
mg g
0.35
1.2
120
240
360
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
c
0
120
240
μg m-3
360
120
240
360
d
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
120
μg m-3
240
360
Fig. 9. Impact of different ozone concentrations (0, 120, 240 and 360 g m-3) on the
photosynthetic pigments content: a – chlorophyll a, b – chlorophyll b, c – total
chlorophyll a and b content, d – chlorophyll a/b ratio in leaves of spring barley plants
Studies of many investigators have indicated that sensitivity of different plant
species to ozone impact is different. Our experimental data showed that spring barley
was not very sensitive to the impact of ozone. Studies in Germany showed that winter
and spring barley were highly resistant to ozone. Visible injury symptoms occurred only
after exposure to higher than 300 g m-3 ozone concentrations (Wu and von
Tiedemman, 2004).
Impact of elevated UV-B radiation on different spring barley cultivars
In this experiment, seven cultivars of spring barley: ‘Aura’, ‘Annabell’, ‘Henni’,
‘Tolar’, ‘Jersey’, ‘Scarlet’ and ‘Barke’ were irradiated with 8 kJ m-2 d-1 UV-B dose.
UV-B radiation caused reduction in the growth of spring barley plants (Fig. 10). After
exposure to UV-B radiation, the height of plants was by 15-26 % less in comparison to
the reference treatment (zero UV-B dose). Differences from the reference treatment
were statistically significant (p0.05) for all investigated cultivars.
‘Tolar’, ‘Annabell’ and ‘Aura’ cultivars were most affected by UV-B radiation,
i.e. their height was reduced by 26.3, 22.9 and 22.7 % respectively. ‘Jersey’ and ‘Henni’
barley were least affected. Their height was by 14.6 and 17.1 % lower respectively,
compared to the reference treatment.
14
Reference
45
Height, cm
40
34.9
32.8
35
30
26.9
33.6
31.9
33.0
31.1
29.2
28.0
26.2
23.5
UV-B
26.2
24.2
24.2
25
20
15
‘Barke’
‘Scarlet’
‘Aura’
‘Henni’
‘Tolar’
‘Jersey’
‘Annabell’
10
Fig. 10. Impact of UV-B radiation on the height of different spring barley cultivars
Data related to the impact of UV-B radiation on the dry weight of different
spring barley cultivars are presented in Figure 11. UV-B radiation caused an essential
reduction in the dry weight of treated plants, in comparison to the reference treatment.
Reference
45
Dry weight, mg aa
40
35
34.2
UV-B
37.0
34.9
35.9
30.2
30.3
30
23.5
25
20
18.7
19.3
19.8
16.1
21.3
15.8
19.2
15
‘Barke’
‘Scarlet’
‘Aura’
‘Henni’
‘Tolar’
‘Jersey’
‘Annabell’
10
Fig. 11. Impact of UV-B radiation on the dry weight of different spring barley cultivars
Lithuanian spring barley cultivar ‘Aura’ was most susceptible to UV-B
radiation. After exposure to UV-B radiation (8 kJ m-2 d-1), dry weight of ‘Aura’ was
reduced by 57 %. ‘Scarlet’ and ‘Henni’ cultivars were most tolerant to UV-B radiation
and their weight decreased by 30 % as compared to reference treatment.
Data on the impact of UV-B radiation on the content of photosynthetic pigments
in the leaves of different spring barley cultivars are presented in Table 1. Without
exposure to UV-B, chlorophyll a content in barley leaves approximated 1 mg g-1
(0.90-1.14 mg g-1). After exposure to UV-B, chlorophyll a content in ‘Jersey’ leaves
increased by 3.2 %, whereas chlorophyll content in other cultivars decreased. The least
decrease in chlorophyll a content – 11.1 % was observed in ‘Henni’ barley leaves, the
greatest change – 36.3 % was detected in ‘Barke’ leaves.
After exposure to UV-B, chlorophyll b content increased in the leaves of
‘Jersey’ and ‘Henni’ cultivars. Chlorophyll b content in others cultivars has decreased.
15
After exposure to UV-B radiation, total content of chlorophyll a+b increased in the
leaves of spring barley cultivar ‘Jersey’ by 4 %. The least content of chlorophyll
a+b losses (3.5 %) were characteristic to ‘Henni’ cultivar and these differences from the
reference treatment were statistically insignificant (p>0.05). Whereas content of
chlorophyll a+b in ‘Tolar’ and ‘Barke’ barley leaves decreased by 35 % after UV-B
exposure.
It was found that the content of carotenoids increased after exposure to UV-B
radiation from 18.5 to 88.9 % in different cultivars.
Table 1. Impact of UV-B radiation on the content of photosynthetic pigments in the
leaves of 7 spring barley cultivars mg g-1
Cultivars
Treatment
Reference
‘Annabell’
UV-B
Reference
‘Jersey’
UV-B
Reference
‘Tolar’
UV-B
Reference
‘Henni’
UV-B
Reference
‘Aura’
UV-B
Reference
‘Scarlet’
UV-B
Reference
‘Barke’
UV-B
a
1.03*0.015
0.66*0.012
0.94*0.001
0.97*0.004
1.10*0.023
0.71*0.001
0.90*0.012
0.80*0.018
1.14*0.015
0.76*0.005
1.07*0.015
0.86*0.002
1.02*0.005
0.65*0.006
Chlorophyll content
b
a+b
0.36*0.011 1,39*0.020
0.33*0,001 0.99*0.012
0,28 0.011 1.22*0.011
0.30 0.008 1.27*0.010
0.33*0.016 1.43*0.017
0.22*0.002 0.93*0.003
0.25 0.029 1.15 0.029
0.30 0.008 1.11 0.010
0.34*0.010 1.48*0.007
0.29*0.012 1.06*0.017
0.31 0.004 1.38*0.012
0.30 0.014 1.16*0.016
0.31*0.004 1.33*0.008
0.21*0.001 0.86*0.008
a/b
2.89*0.098
2.03*0.032
3.40 0.141
3.25 0.087
3.35 0.223
3.22 0.029
3.66*0.457
2.67*0.127
3.38*0.140
2.61*0.089
3.47*0.087
2.89*0.126
3.26*0.023
3.12*0.019
Carotenoids
content
0,31*0.027
0.42*0.001
0.27*0.004
0.51*0.010
0.33*0.008
0.47*0.001
0.27*0.004
0.32*0.003
0.34*0.014
0.54*0.006
0.31*0.001
0.43*0.005
0.30*0.001
0.39*0.004
* - significant difference at p<0.05.
The impact of UV-B on various cultivars was different. According to the
generalized changes in different investigated indices, the cultivars may be ranked from
the least to the most sensitive to ultraviolet-B radiation as follows: ‘Henni’, ‘Scarlet’,
‘Jersey’, ‘Annabell’, ‘Aura’, ‘Barke’ and ‘Tolar’.
Impact of elevated ozone on different spring barley cultivars
The same seven cultivars of spring barley (‘Aura’, ‘Annabell’, ‘Henni’, ‘Tolar’,
‘Jersey’, ‘Scarlet’ and ‘Barke’) were exposed to ozone in the phytotron complex of the
Lithuanian Institute of Horticulture.
Exposure to 240 μg m-3 ozone concentration increased plant height of all 7
cultivars of spring barley (Fig. 12). After exposure to ozone, ‘Scarlet’ barley was by
20 % higher than the reference treatment plants. The height of ‘Tolar’ cultivar, exposed
to ozone, increased by 15 %, ‘Annabell’ cultivar – by 3 %.
16
55
49.0
50 47.7
Height, cm
51.9
50.9
47.5
45.4
45
41.1
47.4
44.8
42.7
Reference
Oз
50.4
48.4
44.1
42.6
40
35
30
25
‘Barke’
‘Scarlet’
‘Aura’
‘Henni’
‘Tolar’
‘Jersey’
‘Annabell’
20
Fig. 12. Impact of ozone on the height of different cultivars of spring barley
Under ozone exposure dry weight of all 7 barley cultivars has decreased
(Fig. 13). Their dry weight decreased from 19 to 39 %. The least changes in biomass as
compared to reference treatment (zero ozone concentration) were observed for ‘Aura’
(19 %) and ‘Scarlet’ cultivars. The greatest changes in dry weight were observed for
‘Barke’ (36 %) and ‘Annabell’ (39 %) cultivars.
350
265.6
Dry weight, mg
300
250
192.3
Oз
Reference
316.0
191.8
200
258.8
167.9
273.8
279.2
249.8
178.1
225.6
201.7
173.1
179.7
150
100
50
‘Barke’
‘Scarlet’
‘Aura’
‘Henni’
‘Tolar’
‘Jersey’
‘Annabell’
0
Fig. 13. Impact of ozone on the dry weight of different spring barley cultivars
After exposure to ozone, total content of chlorophyll a+b in the leaves of all
spring barley cultivars decreased (Table 2). The least losses of chlorophyll a+b (31 %)
were detected for ‘Aura’ cultivar whereas the content of chlorophyll a+b in ‘Henni’
leaves decreased by 44 % and in ‘Scarlet’ leaves – by 52 % as compared to reference
treatment. Data presented in Table 2 shows that the content of carotenoids in the leaves
of all investigated cultivars decreased under ozone exposure. The content of carotenoids
in ‘Jersey’, ‘Annabell’ and ‘Scarlet’ decreased by 20 %, 29 % and 33 %, respectively.
The greatest losses in content of carotenoids were detected for ‘Henni’ cultivar – 41 %.
Table 2. Impact of ozone on the content of photosynthetic pigments in the leaves of 7
17
spring barley cultivars mg g-1
Cultivars Treatment
‘Annabell’
‘Jersey’
‘Tolar’
‘Henni’
‘Aura’
‘Scarlet’
‘Barke’
Reference
O3
Reference
O3
Reference
O3
Reference
O3
Reference
O3
Reference
O3
Reference
O3
a
1.44*0.311
0.73*0.014
1.26*0.078
0.72*0.004
1.19*0.026
0.70*0.068
1.15*0.081
0.60*0.037
1.07*0.052
0.73*0.038
1.17*0.109
0.52*0.121
1.22*0.039
0.66*0.075
Chlorophyll content
b
a+b
0.86*0.512 2.29*0.823
0.24*0.014 0.97*0.026
0.37 0.021 1.63 0.099
0.35 0.008 1.08 0.010
0.36*0.015 1.55*0.039
0.22*0.015 0.92*0.083
0.36*0.037 1.51*0.119
0.24*0.022 0.84*0.057
0.34 0.025 1.41 0.075
0.25 0.024 0.98 0.061
0.41*0.028 1.58*0.138
0.23*0.054 0.76*0.161
0.37*0.018 1.59*0.056
0.27*0.033 0.92*0.104
a/b
2.54 0.727
3.06 0.147
3.36*0.051
2.25*0.087
3.35 0.094
3.24 0.105
3.24*0.099
2.54*0.124
3.18 0.120
2.93 0.141
2.80 0.074
2.33 0.369
3.27*0.078
2.50*0.185
Carotenoids
content
0.38*0.008
0.27*0.015
0.40 0.020
0.32 0.010
0.40*0.006
0.27*0.031
0.37*0.019
0.22*0.006
0.41*0.012
0.27*0.005
0.39 0.028
0.26 0.052
0.38*0.008
0.24*0.011
* - significant difference at p<0.05.
According to the generalized changes in different indices the cultivars were
ranked from the least to the most sensitive to ozone: ‘Aura’, ‘Jersey’, ‘Tolar’, ‘Barke’,
‘Henni’, ‘Annabell’ and ‘Scarlet’. It is necessary to note that sensitivity of investigated
barley cultivars to ozone impact different essentially from their reaction to UV-B
radiation and most sensitive to the impact of ozone were most resistant to the impact of
UV-B.
The impact of UV-B radiation on spring barley under different intensity of
photosynthetically active radiation (PAR)
The threshold of UV-B damage is dependent on the quantity and quality of
photosynthetically active radiation (PAR). In order to evaluate the effect of PAR, spring
barley before exposure to UV-B were grown in different light conditions.
For the first experiment, plants were grown in a greenhouse of the Lithuanian
Institute of Horticulture (LIH), before being transferred to growth chamber. In the
greenhouse plants received a natural amount of photosynthetically active radiation
(PAR) (20000 Lx). For the second experiment, the plants were grown in chambers at
Vytautas Magnus University (VMU) all the time and received a relatively small amount
of PAR (5000 Lx).
Height increment dependence of spring barley on UV-B in different experiments
is presented in Figure 14.
Height increment of barley in the reference treatment and minimal UV-B
radiation (1 kJ m-2 per day) variant differed insignificantly. With increasing dose of
UV-B radiation, height increment of barley of the first experiment, where illumination
was 20000 Lx, remained almost unchanged, while the height of barley of the second
experiment, where intensity of PAR was 5000, was gradually decreasing. Under
18
Height increment, cm
2 kJ m-2 d-1 dose, it statistically reliably (p<0.05) differed from the reference treatment.
Under maximal daily dose of UV-B radiation (10 kJ m-2), height increment of this
experiment was by 28 % lower that in reference treatment.
kJ m-2d-1
Fig. 14. Dependence of spring barley height increment on UV-B radiation: 1 – normal
light – 20000 Lx; 2 – reduced light conditions – 5000 Lx
Dependence of aboveground mass on the dose of UV-B radiation is presented in
Figure 15. Barley, grown under normal light conditions prior to UV-B exposure, had a
considerably greater biomass, and its dependence on the dose of UV-B radiation was
less expressed as in the case when barley was grown under reduced light conditions in
phytotron chambers prior to exposure.
Under maximal daily dose of UV-B radiation (9 kJ m-2), fresh weight of adapted
to normal light barley plants in the first experiment was by 33 % lower than in reference
treatment, while in the second experiment (barley grew under reduced light) this
difference comprised 48 %. Fresh weight of barley exposed to UV-B rays was almost
twice lower.
19
Fresh weight, mg
kJ m-2d-1
Fig. 15. Dependence of spring barley fresh weight on UV-B radiation: 1 – under normal
light – 20000 Lx (the left side); 2 – reduced light conditions – 5000 Lx (the right side)
Dry weight, mg
Dependence of the dry mass on the dose of UV-B radiation is less revealed
(Fig.16). Under daily dose of 9 kJ m-2, biomass of adapted to normal light barley was by
28 %, while that of adapted to reduced light – by 33 % lower than in reference
treatment. The fact that the fresh weight is more affected by UV-B radiation than the
dry one may be explained by the fact that higher UV-B doses cause drying of leaves.
kJ m-2d-1
Fig. 16. Dependence of spring barley dry weight on UV-B radiation: 1 – normal light –
20000 Lx (the left side); 2 – reduced light conditions – 5000 Lx (the right side)
20
mg g-1
Data on the dependence of chlorophyll a content in barley leaves on UV-B
radiation dose are presented in Fig.17. The content of chlorophyll a in the leaves of
adapted to normal light barley in all variants (including the reference treatment) was
statistically significant (p<0.05) higher than in the leaves of barley adapted to reduced
light. Under daily UV-B radiation dose of 9 kJ m-2, chlorophyll a content comprised
only one third of the amount determined in reference treatment, however, in the
experiment where barley was grown under normal light prior to UV-B exposure, the
amount of chlorophyll was also twice lower.
kJ m-2d-1
Fig. 17. Dependence of chlorophyll a content on UV-B radiation: 1 – normal light –
20000 Lx; 2 – reduced light conditions – 5000 Lx
The content of chlorophyll b in reference treatment and that of minimal UV-B
radiation dose (1 kJ m-2 per day) in both experiments was almost the same (Fig. 18).
However, with increasing UV-B radiation dose, the content of chlorophyll b in the
leaves decreased more in the experiment with reduced light. Under maximal daily
UV-B radiation dose (9 kJ m-2), the content of chlorophyll b in the experiment with
normal light conditions was by 47 % lower than in reference treatment. In the
experiment with reduced light – 61 %.
21
mg g-1
kJ m-2d-1
Fig. 18. Dependence of chlorophyll b content on UV-B radiation: 1 – normal light –
20000 Lx; 2 – reduced light conditions – 5000 Lx
Our results were similar to the conclusions of other authors (Caldwell et al.,
1995) who showed that the negative effect of UV-B was stronger when plants received
small amount of photosynthetically active radiation (PAR).
Single and integrated impact of tropospheric ozone and UV-B radiation on
spring barley and adaptation possibilities to the impact of these factors
Adaptation possibilities of spring barley to the single and integrated impact of
ozone and UV-B were performed on the basis of two stage experiments. During the first
(adaptation) stage barley seedlings were adapted for five days to a relatively low UV-B
radiation dose (3 kJ m-2 d-1) or to a relatively low concentration of ozone (120 g m-3).
Other part of plants was grown without exposure to UV-B or ozone (reference
treatment).
In the second (main impact) stage, investigated plants for five days were
exposed to the relatively strong – 9 kJ m-2 d-1 UV-B dose or to 360 g m-3 ozone in
order to evaluate adaptation possibilities to the same factor or possibilities of cross
adaptation. The unaffected during first phase of experiment plants were also exposed to
the same UV-B dose or ozone concentration.
Results demonstrated that after exposure to high ozone concentration
(360 g m-3) or UV-B radiation (9 kJ m-2 d-1) during main impact period, spring barley
grew better when they during the adaptation period were adapted to low ozone
concentration or UV-B dose and plants height increment during main impact period
was higher of that for no adapted plants (Fig. 19). That shows that spring barley affected
by a low ozone concentration or UV-B radiation during the adaptation period adapts not
only to the impact of the same stressor, but to the impact of other stressor as well.
When barley during the adaptation period were adapted to a relatively low
concentration of ozone and in the main impact period were exposed to a high ozone
concentration (O3+O3), height increment of plants were by 6 % higher than the
22
reference treatment. These differences from reference treatment were statistically
insignificant (p>0.05). Barley during the adaptation period adapted to a relatively low
UV-B radiation dose, while in the main impact period exposed to high UV-B radiation
dose (9 kJ m-2 d-1) height increment was by 58 % higher than that of barley which
during the adaptation period was grown without the impact of UV-B or ozone. These
differences from reference treatment were statistically significant (p<0.05).
Height increment, mmnn
160
Adaptation impact
Reference
Ozone
UV-B
140
120
100
80
60
40
20
0
Ozone
Main impact
UV-B
Fig. 19. Height increment of spring barley over the period of the main impact, mm
(adaptation impact – 3 kJ m-2 d-1 UV-B or 120 µg m-3 O3, main impact – 9 kJ m-2 d-1
UV-B and 360 µg m-3 O3)
Cross-adaptation studies have shown that barley affected during the adaptation
period to a low UV-B dose, while in the main impact period subjected to a high ozone
concentration, have adapted to a certain degree to the impact of another stressor as well.
Height increment of barley in this variant was on an average by 26 % higher and
statistically significant (p<0.05) than that of plants grown in the reference treatment in
the first stage. Similar cross-adaptation effect was determined when barley affected in
the adaptation period by a low ozone concentration (120 µg m-3), while in the main
impact period subjected to a high UV-B dose (9 kJ m-2 d-1). Height increment of barley
in this variant was on an average by 25 % higher than that of plants grown without
adaptation in the first stage.
Data on the content of photosynthetic pigments in different variants of the
experiment are provided in Fig. 20. In the variant of high ozone concentration the
content of chlorophyll a in barley leaves was higher than in previously unaffected one,
in the case when plants were adapted to a weak UV-B dose. In the period of the main
impact, having exposed plants to an intensive UV-B radiation, higher concentration of
chlorophyll a was found in the leaves of unadapted plants. Similar tendencies were
ascertained in the studies of chlorophyll b as well as total amount of chlorophyll a+b.
23
-1
mg g
1.4
1.2
1
0.8
0.6
0.4
0.2
0
a
-1
mg g
Ozone
b
UV-B
0.4
0.2
0
UV-B
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Ozone
c
UV-B
0.8
d
0.6
0.4
0.2
0
Ozone
-1
Reference
0.6
Ozone
mg g
Adaptation impact
0.8
UV-B
3.5
3
2.5
2
1.5
1
0.5
0
Ozone
e
Ozone
UV-B
Main impact
UV-B
3.5
3
2.5
2
1.5
1
0.5
0
f
Ozone
UV-B
Main impact
Fig. 20. Content of photosynthetic pigments: a – chlorophyll a content; b – chlorophyll
b content; c – a+b; d – amount of carotenoids; e – a/b; f – carotenoids/a+b
The leaves of barley, when plants were grown without any stressors (absolute
control) contained about 0.38 mg g-1of carotenoids. The amount of carotenoids in the
leaves of spring barley, exposed to ozone, decreased. Meanwhile, UV-B radiation
stimulated the formation of higher amounts of carotenoids in the leaves of spring barley.
Adaptation mechanisms haven‘t been elicited yet, but it is known that plants
employ different protection systems to avoid stressors. It was ascertained that the
reaction of plants to stressors is similar (Krupa, 2003; Fujibe et al., 2004). The impact
mechanisms of ozone and UV-B radiation are similar as well (Willekens et al., 1994).
A. Polle (1997) has proved that low UV-B radiation can stimulate antioxidation systems
and induce cross-tolerance to other environmental stressors. Our studies have shown
that adaptation doses of UV-B radiation increased the tolerance of plants to extreme
ozone concentrations.
24
Conclusions
1. Having conducted studies on UV-B radiation impact on spring barley, it was
found that UV-B radiation of even 3 kJ m-2 d-1 caused observable damages on
barley leaves, by about 30% decrease in fresh and dry biomass as well as the
total content of chlorophylls a+b, meanwhile, in the variant with 9 kJ m-2 d-1
UV-B radiation dose, the content of chlorophylls decreased approximately two
times.
2. Biochemical analysis has shown that 3 kJ m-2 d-1 UV-B radiation causes the
increase of the total glutathione concentration in the tissues of barley leaves by
more than three times. The effect of UV-B radiation reduced also the ratio of
reduced and oxidized glutathione. The leaves of the reference treatment plants
contained 49.7 % of reduced glutathione from the total amount, meanwhile, in
the leaves affected by UV-B radiation it decreased down to 35.4 %.
3. Studies have shown that increasing ozone concentration had no statistically
significant impact to height growth however inhibited biomass accumulation of
spring barley. 360 µg m-3 ozone concentration reduced fresh biomass by about
32 %. The content of chlorophylls a and b decreased most in the variant with
360 µg m-3 ozone concentration and this reduction comprised about 35 %. The
ratio of chlorophyll a/b remained almost unchanged.
4. The resistance of different cultivars to UV-B radiation differed. The most
sensitive to UV-B radiation was detected to be the Lithuanian cultivar ‘Aura’ as
well as foreign cultivars – ‘Barke’ and ‘Tolar’. As the most tolerant to UV-B
radiation were detected ‘Henni’, ‘Scarlet’ and ‘Jersey’ cultivars.
5. The sensitivity of different barley cultivars to ozone impact differed from their
reaction to UV-B radiation. ‘Aura’, ‘Tolar’ and ‘Jersey’ occurred to be most
tolerant, while ‘Henni’, ‘Scarlet’ and ‘Annabell’ cultivars – sensitive to ozone
impact.
6. Having compared the sensitivity of different barley cultivars to UV-B radiation
and ozone impact, it can be seen that the reaction of the same cultivars to
different stressors greatly differs. ‘Aura’ and ‘Tolar’ cultivars were sensitive to
UV-B impact, however, resistant to ozone. ‘Henni’ and ‘Scarlet’, on the
contrary, were sensitive to ozone, but resistant to UV-B radiation.
7. The sensitivity of spring barley to UV-B radiation depends on the intensity of
photosynthetically active radiation. Under maximal investigated daily UV-B
doze (9 kJ m-2), fresh biomass of adapted to normal light (20000 Lx) plants
decreased by one-third, while that of grown under reduced light (5000 Lx) –
almost twice.
8. Studies of spring barley adaptation possibilities to UV-B radiation and ozone
impact have shown that barley adapts not only to the impact of the same
stressor, but to the impact of other stressors as well. Studies of barley adaptation
possibilities to the impact of the same stressor have revealed that height
increment of barley affected during the adaptation period by a relatively low,
while during the main impact period by a high UV-B dose, was by 58 % higher
than in barley grown without preliminary adaptation.
9. Cross-adaptation studies have shown that barley affected during the adaptation
period by a low UV-B dose, while in the main impact period subjected to a high
ozone concentration, have adapted to a certain degree to the impact of another
25
stressor as well. Height increment of barley in this variant was on an average by
26 % higher than that of plants grown in the reference treatment in the first
stage. Similar cross-adaptation process was determined when barley was
affected during the adaptation period by a low ozone concentration (120 µg m-3),
while in the main impact period subjected to a high UV-B dose (9 kJ m-2 d-1).
Height increment of barley in this variant was on an average by 25 % higher
than that of plants grown without adaptation in the first stage.
10. An increased content of chlorophylls (a, b, a+b), as compared to unadapted
plants, was most often ascertained when in the main impact period plants were
affected by a high ozone concentration, being primarily adapted to a low UV-B
radiation. The content of carotenoids, as compared to unadapted plants, was
higher in the variant of high ozone concentration with a prior adaptation to a low
UV-B dose, as well as in plants of both stages, affected by UV-B radiation.
26
List of publication
In peer-reviewed journals, referred in Intrnational scienticic databases:
1. Dėdelienė K., Brazaitytė A., Stankevičiūtė S. 2006. Vasarinių miežių adaptacija
prie diferencijuoto ir kompleksinio UV-B ir ozono poveikio. Sodininkystė ir
daržininkystė. Mokslo darbai. 25 (2), p. 107-117. ISSN 0236-4212
2. Brazaitytė A., Juknys R., Sakalauskaitė J., Šikšnianienė J.B., Januškaitienė I.,
Dėdelienė K., Sliesaravičius A., Ramaškevičienė A., Juozaitytė R., Šlepetys J.,
Kadžiulienė Ž., Lazauskas S., Duchovskis P. 2006. Žemės ūkio augalų fotosintezės
sistemos tolerancija ozono ir UV-B spinduliuotės stresui. Sodininkystė ir daržininkystė.
Mokslo darbai. 25 (2), p. 14-24. ISSN 0236-4212
3. Juknys R., Duchovskis P., Sliesaravičius A., Šlepetys J., Martinavičienė J.,
Brazaitytė A., Juozaitytė R., Lazauskas S., Dėdelienė K., Sakalauskaitė J., Romaneckienė
R., Kadžiulienė Ž., Januškaitienė I. 2006. Anglies dioksido ir temperatūros
diferencijuotas bei kompleksinis poveikis žemės ūkio augalams. Sodininkystė ir
daržininkystė. Mokslo darbai. 25 (2), p. 3-13.
4. Juknys R., Dėdelienė K., Martinavičienė J., Blažytė A., Duchovskis P.,
Šikšnianienė J.B., Brazaitytė A. 2005. Vasarinių miežių (Hordeum sativum L.) jautrumo
ultravioletinei (UV-B) spinduliuotei tyrimai. Sodininkystė ir daržininkystė. Mokslo
darbai. 24 (2), p. 97-104. ISSN 0236-4212
5. Blažytė A., Dėdelienė K., Juknys R., Martinavičienė J., Brazaitytė A.,
Duchovskis P., Ramaškevičienė A. 2005. Kadmio ir vario poveikis ir augalų adaptacija
prie šių metalų. Sodininkystė ir daržininkystė. Mokslo darbai. 24 (2), p. 113-121. ISSN
0236-4212
In conferences proceedings and other publications:
1. Dėdelienė K., Brazaitytė A., Stankevičiūtė S. 2006. Vasarinių miežių adaptacija
prie diferencijuoto ir kompleksinio UV-B ir ozono poveikio. Mokslinės konferencijos
“Augalų adaptyvumo didinimo ekologiniai ir biotechnologiniai aspektai” medžiaga
[LSDI, Babtai, 2006 birželio 30]. Sodininkystė ir daržininkystė. Mokslo darbai. 25 (2), p.
107-117.
2. Dedeliene K., Baranauskis K., Sabajaviene G. 2005. Impact of ozone on spring
barley (Hordeum sativum ssp.) photosynthetic pigments. Tarptautinės konferencijos
“EcoBalt’2005” medžiaga [Riga, May 5-6, 2005]. – Ryga, 2005. – p. 12-13.
3. Blažytė A., Dėdelienė K. 2004. Augalų adaptacijos prie aplinkos stresorių
poveikio tyrimai. 7-osios Lietuvos jaunųjų mokslininkų konferencijos ”Lietuva be
mokslo – Lietuva be ateities“ medžiaga [VGTU, Vilnius 2004 kovo 25]. – Vilnius:
Technika, 2004. – p. 291-296.
CURRICULUM VITAE
Name:
KRISTINA DĖDELIENĖ
Date of the birth
28 March, 1979
Education:
1985-1997
Kybartai K.Donelaitis Secondary school, Vilkaviškis district,
Lithuania
1997-2001
Lithuanian University of Agriculture, Akademija, Kaunas district,
Lithuania. BSc in Agriculture Sciences
2001-2003
Lithuanian University of Agriculture, Akademija, Kaunas district,
Lithuania. MSc in Agriculture Sciences
2003-2007
PhD student in Department of Environmental Sciences, Vytautas
Magnus University
Research and professional experiences:
2004-2006
2007 09
Department of Environmental Sciences, Vytautas Magnus
University, Kaunas, Lithuania. Project “Integrated impact of
antropogenic climatic and environmental changes to the vegetation
of forest and agro-ecosystems”, laboratory Assistent
Department of Environmental Sciences, Vytautas Magnus
University, Kaunas, Lithuania. Research Assistent
Reziumė
Vis aktualesnės tampa aplinkos problemos, susijusios su ozono kiekio pokyčiais
stratosferoje ir troposferoje. Nuo XX amž. aštuntojo dešimtmečio pradžios fiksuojamas
gana spartus stratosferos ozono sluoksnio irimas (Krizek et al., 1998). Įvairių institucijų
tyrimų duomenimis stratosferos ozono sluoksnis nuo 1980 pradžios žymiai suplonėjo,
1997-2001 metais vidutinis ozono sluoksnis pasaulyje buvo 3 % plonesnis negu 1980
metais (WMO, 2003). Europoje per šį laikotarpį ozono sluoksnis suplonėjo apie 7 %
(EEA, 2003).
Ozono sluoksnis sugeria didelę dalį ultravioletinių spindulių ir apsaugo augalus
bei kitus gyvus organizmus nuo žalingo poveikio. Ozono sluoksnio storis lemia UV-B
spindulių srautą, todėl yrant ozono sluoksniui, didžiausią pavojų augalijai kelia ši
ultravioletinės spinduliuotės spektro dalis (Cicerone, 1987).
Kita su ozonu susijusi problema yra pagrindinio ozono pirmtako – azoto dioksido
koncentracijos didėjimas troposferoje ir gana spartus priežemio ozono koncentracijos
augimas. Priežemio ozono susidarymas yra endoterminė reakcija, jos vyksmą visų pirma
sąlygoja į troposferą patenkančių ultravioletinių spindulių (UV) kiekis. Ultravioletiniai
spinduliai skatina NO2 fotolizę (Thompson et al., 1991; Wayne, 2000).
Per pastaruosius 20 metų Lietuvoje priežemio ozono koncentracija kasmet
padidėjo po 0,9 µg m-3 (Girgždienė, Girgždys, 2003). Lietuvoje ozono koncentracija kai
kuriais metų laikais viršija leistiną lygį. Vidutinė paros ozono koncentracija padidėjimo
periodu viršija 65 µg m-3 lygį, kurį Pasaulinė sveikatos organizacija rekomenduoja
laikyti paros ribine koncentracija.
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Vidutinė UV-B spinduliuotės paros dozė Lietuvoje saulėtomis vasaros dienomis
gali būti 2,5 kJ m-2 d-1 (Chadyšienė et al., 2005), o kitose platumose UV-B srauto
intensyvumas pakyla iki 11 kJ m-2 d-1 (Frederick et al., 2000).
Įvairių autorių atlikti tyrimai rodo, kad UV-B spinduliuotės poveikis augalams yra
gana įvairiapusis. Dėl UV-B spinduliuotės poveikio sumažėja daugelio rūšių augalų
augimas, žalioji ir sausoji biomasė, chlorofilų ir karotinoidų kiekis (Ambasht, Agrawal,
1997, 1998; Correia et al., 1999a; Mazza et al., 1999; Nasser, 2001). Nustatytas
statistiškai patikimas UV-B spinduliuotės poveikis miežių augimo parametrams –
aukščiui, atžalų kiekiui, lapo plotui, biomasei (Nasser, 2001). Tyrimuose su žaliąja
kreisve (Crepis Capillaris (L.)) nustatyta, kad net nedidelės UV-B dozės – 1 kJ m-2 d-1
labai paveikia augalo augimą, SOD aktyvumą ir baltymų kiekį lapuose, genų, lemiančių
kiekybinius požymius, raišką (Rančelienė ir kt., 2005).
Priežemio ozono poveikio tyrimai miško ir lauko augalams rodo, kad didesnės
koncentracijos priežemio ozonas sukelia įvairius išorinius augalų pažeidimus, sulėtina jų
augimą bei padidina jautrumą kitiems natūraliems ir antropogeniniams stresoriams
(Skärby, 1994; Küppers et al., 1994; Miller et al., 1994). Nustatyta, kad net nedidelės
koncentracijos ozonas slopina jautrių augalų (ankštinių, javų) fotosintezę, vystymąsi ir
augimą (Fiscus et al.,1994; Fiscus and Booker, 1995; Krupa, Kirckert, 1989). Nustatyta,
kad ozonas kaip itin stiprus oksidatorius sukelia augalų oksidacinį stresą, pažeidžia
ląstelių membranas ir plazmą, sutrikdo medžiagų apykaitos ir informacijos srautus,
skatina senėjimo procesus (Ludwikow et al., 2004).
Natūraliai gamtoje vienas teršalas niekada neveikia, organizmai ir ekosistemos yra
veikiami daugelio skirtingų teršalų ir jų darinių. Didėjanti priežemio ozono koncentracija
ir UV-B spinduliuotė daro neigiamą poveikį augalams, sukelia neigiamus jų morfologijos
ir fiziologijos pokyčius (Runeckles and Krupa, 1994; Caldwell et al., 1995). Tačiau yra
duomenų, kurie rodo, kad nedidelė UV-B spinduliuotė gali turėti netgi palankų poveikį
augalų streso tolerancijai. Pavyzdžiui, pušų sodinukai buvo mažiau pažeisti ozono, kai
prieš tai buvo paveikti UV-B spinduliuote. UV-B spinduliuotė sumažino žalingą ozono
poveikį (Schnitzler et al., 1999).
Augalų prisitaikymo galimybės prie besikeičiančių aplinkos ir klimato sąlygų yra
itin aktualus klausimas ir turi neabejotiną praktinę reikšmę. Natūralioje aplinkoje
didėjantis ozono ir UV-B spinduliuotės intensyvumas paskatino atlikti vasarinių miežių
augimo tyrimus kontroliuojamomis sąlygomis. Nors nemažai darbų atlikta detalizuojant
diferencijuotą UV-B spinduliuotės ir ozono įtaką augalams, tačiau kompleksinis šių
veiksnių poveikis yra palyginti mažai tyrinėtas. Lietuvoje tokio pobūdžio tyrimai
vykdomi nuo 2003 pagal Lietuvos valstybinio mokslo ir studijų fondo finansuojamą
projektą “Antropogeninių klimato ir aplinkos pokyčių kompleksinis poveikis miškų ir
agroekosistemų augmenijai”.
Darbo tikslas – ištirti priežemio ozono ir ultravioletinės (UV-B) spinduliuotės
poveikį vasariniams miežiams bei miežių adaptacijos prie diferencijuoto ir kompleksinio
šių veiksnių poveikio galimybes.
Darbo hipotezė. Augalai fiziologiškai prisitaikę prie vieno stresoriaus poveikio
tampa atsparesni ne tik to paties, bet ir kitų neigiamų aplinkos veiksnių poveikiui.
Tyrimų objektu buvo pasirinkti vasariniai miežiai (Hordeum vulgare L.), kaip
vieni plačiausiai auginamų miglinių augalų Lietuvoje. Eksperimentai buvo atlikti Vytauto
Didžiojo universiteto Aplinkotyros katedros ir Lietuvos sodininkystės ir daržininkystės
Fiziologijos laboratorijos fitokamerų komplekse. Nustatytos vasarinių miežių tolerancijos
sritys skirtingo intensyvumo priežemio ozono ir suintensyvėjusios UV-B spinduliuotės
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poveikiui. Atlikti skirtingų veislių miežių reakcijos į šių veiksnių poveikį tyrimai.
Siekiant išsiaiškinti vasarinių miežių adaptacijos prie UV-B ir ozono poveikio galimybes
buvo atlikti tyrimai, kurie parodė, kad adaptacinio poveikio metu miežiai paveikti silpna
UV-B spinduliuotės doze ar ozono koncentracija, prisitaikė ne tik prie to paties, bet ir
prie kito iš tirtų veiksnių poveikio.
Remiantis tyrimų rezultatais padarytos tokios išvados:
1. Nustatyta, kad jau 3 kJ m-2 d-1 UV-B spinduliuotė sukėlė matomus miežių
lapų pažeidimus, apie 30 % sumažino žaliosios ir sausosios biomasės kaupimąsi bei
chlorofilų a ir b sintezę, o 9 kJ m-2 d-1 UV-B spinduliuotės dozės variante chlorofilų
kiekis sumažėjo du kartus.
2. Biocheminė analizė parodė, kad dėl 3 kJ m-2 d-1 UV-B spinduliuotės dozės
poveikio miežių lapų audiniuose daugiau negu tris kartus padidėja bendra glutationo
koncentracija. Taip pat UV-B poveikyje nustatytas glutationo redukuotos bei oksiduotos
formų santykio sumažėjimas. Kontrolinių augalų lapuose redukuotas glutationas sudarė
49,7 % bendro jo kiekio, tuo tarpu UV-B spinduliuote paveiktų augalų lapuose jis
sumažėjo iki 35,4 %.
3. Padidėjusi ozono koncentracija neturėjo esminės įtakos vasarinių miežių
augimui į aukštį, skatino naujų lapų genezę ir tįstamąjį augimą, tačiau slopino
biomasės kaupimąsi. 360 μg m-3 ozono poveikyje miežių žalioji biomasė sumažėjo apie
32 %. Ozonas slopino tiek chlorofilo a, tiek chlorofilo b sintezę. Chlorofilų a ir b kiekis
360 µg m-3 ozono poveikyje sumažėjo apie 35 %, o jų santykis beveik nepakito.
4. Skirtingų miežių veislių atsparumas UV-B spinduliuotei buvo nevienodas.
Jautriausiai į UV-B spinduliuotės poveikį reagavo lietuviška veislė ‘Aura’ bei užsienio
veislės – ‘Barke’ ir ‘Tolar’. Tolerantiškiausios UV-B poveikiui buvo ‘Henni’, ‘Scarlet’ ir
‘Jersey’ veislės.
5. Tirtų miežių veislių jautrumas ozono poveikiui labai skyrėsi nuo jų jautrumo
UV-B poveikiui. ‘Aura’ ir ‘Tolar’ veislės įvertintos kaip tolerantiškos ozono poveikiui, o
‘Henni’ ir ‘Scarlet’ kaip veislės jautrios ozono poveikiui.
7. Vasarinių miežių jautrumas UV-B spinduliuotei priklauso nuo fotosintetiškai
aktyvios spinduliuotės intensyvumo. Esant maksimaliai iš tirtų UV-B spinduliuotės paros
dozei (9 kJ m-2), adaptuotų prie normalios šviesos (20000 Lx), augalų žalioji biomasė
sumažėjo trečdaliu, o silpnesnėje šviesoje (5000 Lx) augintų – beveik du kartus, todėl
interpretuojant UV-B poveikio rezultatus būtina atsižvelgti į FAS intensyvumą bandymų
metu.
8. Vasarinių miežių adaptacijos prie UV-B spinduliuotės ir ozono poveikio
galimybių tyrimai parodė, kad miežiai prisitaikė ne tik prie to paties, bet ir prie kito iš
tirtų veiksnių poveikio (kryžminė adaptacija). Tiriant miežių adaptacijos galimybes prie
to paties veiksnio poveikio, nustatyta, kad adaptacinio periodu metu paveiktų sąlygiškai
silpna (3 kJ m-2 d-1), o pagrindinio etapo metu – stipria UV-B doze (9 kJ m-2 d-1), aukščio
prieaugis buvo 58 proc. didesnis, nei be išankstinės adaptacijos augintų miežių prieaugis.
Ozono atveju adaptacijos prie to paties veiksnio reiškinys nebuvo toks efektyvus, miežių
aukščio prieaugis šiame variante vidutiniškai buvo tik 6 % didesnis, nei miežių,
pirmajame poveikio etape augintų kontrolinėje kameroje, prieaugis.
9. Kryžminės adaptacijos tyrimai parodė, kad miežių adaptaciniame etape veiktų
silpna UV-B doze (3 kJ m-2 d-1), o pagrindinio poveikio metu patyrusių didelės ozono
koncentracijos (360 µg m-3) poveikį adaptavosi ir prie kito veiksnio poveikio. Miežių
aukščio prieaugis šiame variante vidutiniškai buvo apie 26 proc. didesnis, nei pirmajame
etape kontrolinėje kameroje augusių augalų. Panašus kryžminės adaptacijos reiškinys
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užfiksuotas ir tuo atveju, kai adaptacinio periodo metu miežiai patyrė sąlygiškai silpną
(120 µg m-3) ozono poveikį, o pagrindinio poveikio metu buvo paveikti stipria UV-B
doze (9 kJ m-2 d-1). Šiame variante miežių prieaugis į aukštį buvo 25 proc. didesnis, nei
be išankstinės adaptacijos augintų miežių prieaugis.
10. Chlorofilų kiekio pokyčiai nebuvo tokie dėsningi, kaip augimo intensyvumo
atveju. Padidėjęs chlorofilų (a, b, a+b) kiekis, lyginant su neadaptuotais augalais, buvo
nustatytas tik tuo atveju, kai augalai buvo adaptuoti prie silpno UV-B spinduliuotės
poveikio, o pagrindinio poveikio periodu paveikti didele ozono koncentracija.
Karotinoidų kiekis buvo didesnis, lyginant su neadaptuotais augalais, didelės ozono
koncentracijos ir prieš tai adaptuotame prie silpnos UV-B dozės variante, taip pat
abiejuose tyrimo etapuose patyrusių UV-B spinduliuotės poveikį.
31