THE EFFECT OF ACID RAIN ON ULTRASTRUCTURE AND FUNCTIONAL PARAMETERS OF PHOTOSYNTHETIC APPARATUS OF PEA LEAVES
A.V. Polishchuk,1 M.V. Vodka, N.A. Belyavskaya, A.P. Khomochkin, E.K. Zolotareva
M.G. Kholodhy Institute of Botany, Nat. Acad. Sci. of Ukraine, Kiev, Ukraine;
1 e-mail: polishch@yandex.ru
The effects of simulated acid rain (SAR) on the ultrastructure and functional parameters of the photosynthetic apparatus were studied using 14-day-old pea leaves as test system.
Pea plants were sprayed with an aqueous solution containing NaNOsub>3 (0.2 mM) and Na2SO4 (0.2 mM) (pH 5.6, a control variant), or with the
same solution, which was acidified to pH 2.5 (acid variant). Functional characteristics were determined by chlorophyll fluorescence analysis. Acid rain application caused reduction in
the efficiency of the photosynthetic electron transport by 25 %, which was accompanied by an increase by 85 % in the quantum yield of thermal dissipation of excess light quanta.
Ultrastructural changes in chloroplast were registered by transmission electron microscopy (TEM) after two days of the SAR-treatment of pea leaves. In this case, the changes in the
structure of grana, heterogeneity of thylakoids packaging in granum, namely, the increase of intra-thylakoid gaps and thickness of granal thylakoids compared to the control were found.
The migration of protein complexes in thylakoid membranes of chloroplasts isolated from leaves treated with SAR was suppressed. It was shown also that carbonic anhydrase activity
was inhibited in chloroplast preparations isolated from SAR-treated pea leaves. We proposed a hypothesis on the possible inactivation of thylakoid carbonic anhydrase under SAR and
its involvement in the inhibition of photochemical activity of chloroplasts. The data obtained allows to suggest that acid rains negatively affect the photosynthetic apparatus disrupting
the membrane system of chloroplast.
Key words:
Pisum sativum L., acid rains, bicarbonate, chloroplast, grana, photosynthetic apparatus, thylakoids
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