Alterations in Indoleacetic Acid, Abscisic Acid and Aminocyclopropane Carboxylic Acid in Pea Plants after Prolonged Influence of Low Levels Ultraviolet-b and Ultraviolet-c Radiations

The response of pea (Pisum sativum L., cv. Scinado) plants to low UV-B and UV-C radiation levels was studied in the 2nd leaves in relation to IAA, ABA and ACC contents. Following regimes of UV-B and UV-C radiation were used for 7, 10 or 14 consecutive days: B1 (4.4 kJ m-2 d-1), B2 (13.3 kJ m-2 d-1) and C1 (0.1 kJ m-2 d-1) and C2 (0.3 kJ m-2 d-1). As compared to control, IAA decreased after 10 days of C2 irradiation, although B1 regime caused an increase. At the end of the experiment IAA was raised in C2-treated plants. ABA increased transiently in B1-treated plants (10d B1) but it dropped at the end of the experiment (14d UV) after both UV-B and UV-C irradiations. With one exception (7d B1), ACC accumulated in the treated plants. The increases in IAA and ABA concentrations after 10 days of B1 regime was interpreted in relation to plant adaptation. Moderate accumulation in ACC in C1-and B1-treated plants could also be connected with stimulation of ethylene signal pathway that is needed for the defence system against UV-induced damage.