Evidence against the involvement of phytochrome in UVB-induced inhibition of stem growth in green tomato plants

摘要: The effects of UVB on the kinetics stem elongation wild type (WT) and photomorphogenic mutants tomato were studied by using linear voltage transducers connected to a computer. Twenty-one or twenty-six-day-old plants, grown in 12 h white light (150 μmol m−2 s−1 PAR)/12 dark cycles, first transferred 200 monochromatic yellow for h, then irradiated with 0.1 4.5 finally kept darkness another 24 h. measurements started after 4 under light. Significant differences growth during irradiation light, as well period, found between genotypes. In darkness, magnitude followed order: tri > AC = fri MMau hp1. Two factors determined large darkness: 1) different rate (SER) 2) duration growing phase among au hp1 lasted about 18 whereas it continued whole experimental period (36 h) other substantially reduced all genotypes (4.5 being more effective than s−1). Both fluence rates induced detectable reduction SER already 15 min irradiation. Red inhibited, while far red promoted tested. (phyA null), (phyB1 (exhibiting exaggerated phytochrome responses) WT showed similar levels UVB–induced inhibition growth, aurea mutant largest These results indicate that is not directly involved control elongation. dichromatic irradiations + presence distinct additive action photoreceptor system photoregulation growth.