Ethylene evolution and ABA and polyamine contents in Arabidopsis thaliana during UV-B stress

Changes in plant growth, membrane integrity, ethylene evolution, ABA content, and the content of free polyamines were examined in 14-day-old Arabidopsis thaliana (L.) Heynh., strain Columbia (Col-0) plants after a single UV-B irradiation with low (3 kJ/m2), moderate (6–9 kJ/m2), high (18 kJ/m2), and lethal (27 kJ/m2) doses. The UV-B treatment caused dose-dependent suppression of plant growth. One hour after irradiation, the membrane damage was evident from the increased leakage of electrolytes. The low-dose and moderate-dose irradiation caused a transient increase in evolution of ethylene and in the content of putrescine (spermidine and spermine precursor) with the peaks of these parameters attained at 5 and 24 h, respectively. The high-and lethaldose irradiation induced a smaller rise in ethylene evolution, with a slight trend to its decrease, especially, after the exposure to the lethal dose. The high and lethal doses of UV-B suppressed putrescine accumulation, depleted spermidine and spermine pools, and caused severe injuries and plant death. During the first day after irradiation, the ABA content increased in proportion to the irradiation dose. On the second day, the accumulation of ABA was observed in plants irradiated with moderate doses. The accumulation was arrested after a high-dose irradiation and was diminished by 45% after a lethal dose treatment. The results provide evidence for the involvement of ethylene, ABA, and polyamines in plant responses induced by UV-B irradiation.