Changes in the activity of antioxidant enzyme superoxide dismutase ...

UVB and ozone and to answer the question whether enzyme of antioxidative stress
SOD participates in protective mechanisms of plant.
Object, methods and conditions. Crepis capillaris (L.) Wallr. plants grown for 2
weeks in a phytotron at the Laboratory of Cell Engineering of the Institute of Botany
and later transferred into the phytotron of the Lithuanian Institute of Horticulture
were used. Growth regime – 16/8 hour photoperiod; 21/16 °C day/night temperature.
The plants were divided into groups of unequal size: control (K) – unaffected plants;
plants affected by ozone or UVB, i.e. affected for 5 days by low adaptive doses: or
3 kJ m -2 d -1 (UVB), or 120 µg m -3 ozone (O 3
), respectively. During the second stage of
the research the first portion of plants was divided into 3 groups: control – unaffected
plants (K + K) affected plants by threefold dose (without adaptation): UVB (9 kJ m -2 d -1 )
or ozone (360 µg m -3 ), marked (K + UV) and (K + O 3
), respectively. Second group of
plants adapted by UVB or ozone was also affected by the same threefold doses only in
various combinations: combining the first impact with the second one: UVB + UVB;
O 3
+ O 3
; UVB + O 3
; O 3
+ UVB. During the second stage of the research exposition
to UVB or ozone was 7 days.
Activity of superoxide dismutase (SOD, EC 1.15. 1.1). Leaf material (1g) was
grounded with extraction buffer (2 ml), consisting of 1mM EDTA, 0.1 % Triton
X-100 in 0.05M Na-K phosphate buffer pH 7.8, with mortar and pestle at 4 °C. The
homogenates were centrifuged for 15 min at 12,000 Ч g (4 °C), and supernatants were
used as crude extract for soluble protein quantification according to Bradford (1976)
with bovine serum albumin as the standard.
Total SOD activity was assayed by the inhibition of the photochemical reduction
of nitro blue tetrazolium (NBT) according to modified method of Beyer and Fridovich
(1987). The reaction mixture (2.2 ml) consisted of 50 mM (Na-K) phosphate (pH 7.8)
and 20 µl of leaves extracts. Each extract was assayed twice with three replications
and measured by spectrophotometer at 560 nm.
The statistical data analysis was carried out by packet of statistical analysis tools
of MS Exel 2002 (Microsoft Corporation) program.
Results. It has been determined that in the course of adaptation, after 5 days
treatment (i. e. first measurement) by low UVB (3 kJ m -2 d -1 ) or ozone (120 µg m -3 )
doses the concentration of soluble proteins decreased comparing with the control (K).
The decrease was particularly significant after ozone treatment (table).
Table. Protein content changes after UVB and ozone treatment in leaves of Crepis
capillaris plants. Protein, mg g -1 F. w.; F. w. – fresh weight.
Lentelė. Baltymo kiekio pokyčiai po UV ir ozono poveikių Crepis capillaris augalų
lapuose, mg g -1
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