UV-B RADIATION CAUSES CHANGES IN INTRACELLULAR LEVELS OF NICOTINAMIDE, TRIGONELLINE AND GLUTATHIONE IN PISUM-SATIVUM LEAVES

Three different doses of supplementary W-B radiation (the biologically effective dose rate normalized to 300 nm, UV-B-BE,B-300, being 0.18, 0.32 or 1.4 W m(-2)) were used to irradiate Pisum sativum plants. Expo sed leaves and control leaves were assayed for the content of nicotina mide (NIC), trigonelline (TRIG), and glutathione (both the oxidized fo rm, GSSG, and total glutathione, GSH(tot)). The NIC, TRIG, GSH(tot) an d GSSG levels did not change in leaves exposed to the two lowest dose rates of UV-B. 1.4 W m(-2) W-B-BE,B-300 maximally gave rise to a 60-fo ld increase in GSSG and a 4.5-fold increase in GSH(tot), whereas a 3.5 -fold increase in NIC and a 9.5-fold elevation in TRIG were obtained. The results obtained are discussed in terms of a proposed role(FEBS Le tt. 351 (1994) 145-149) for NIC/TRIG as secondary messengers in plant cells under stress.