1,720,994 research outputs found
Time-dependent effectiveness of Uv tratment on the control of the elongation growth of tomato transplants
No full textInteractions of phytochromes A, B1 and B2 in light-induced competence for adventitious shoot formation in hypocotyl of tomato (Solanum lycopersicum L.)
No full textPhotomorphogenic responses to UV radiation IV: A comparative study of UVB effects on growth and pigment accumulation in etiolated and de-etiolated hypocotyls of wild-type and aurea mutant of tomato (Lycopersicon esculentum Mill.)
No full textEvidence against the involvement of phytochrome in UVB-induced inhibition of stem growth in green tomato plants
No full textPhytochrome A and phytochrome B1 control the acquisition of competence for shoot regeneration in tomato hypocotyl
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An analysis of UV-A effects on phytochrome-mediatged induction of phenylalanine ammonia-lyase in the cotyledons of Lycopersicon esculentum Mill.
No full textA 15-min exposure with UV-A light (320–400 nm) significantly increased the extractable activity of phenylalanine ammonia-lyase (PAL) 4 hr after the onset of the light treatment. The effect produced by a 15-min UV-A exposure was completelt reversed by a consecutive brief exposure to far red light. The UV-A- and red-mediated increases in PAL activity appear to be very similar with continuous exposure. Seedlings grown under 5 W/m2 UV-A supplemented with blue, far red, and white light showed less PAL activity than control seedlings (i.e. exposed to blue, far red, and white light alone). Seedlings grown under 5W/m2 UV-A supplemented with red light showed the same PAL activity as control seedlings exposed to UV-A and red light alone.
It appears that prolonged UV-A exposure does not affect the response to continuous red light, but it is able to decrease significantly PAL activity in the blue and far red part of the spectrum. Furthermore, the positive and the inhibitory effects of prolonged UV-A irradiation demonstrate a different fluence rate requirement. The data indicated that phytochrome and a separate UV-A photoreceptor are involved in the photoregulation of PAL activity in cotyledons of tomato plant
Light Quality Influences Indigo Precursors Production And Seed Germination In Isatis tinctoria L. And Isatis indigotica Fort
No full textIsatis tinctoria L. and Isatis indigotica Fort. are biennial herbaceous plants belonging to the family of Cruciferae that are used as a source of natural indigo and show several morphological and genetic differences. Production of indigo (indigotin) precursors, indican (indoxyl β-D glucoside) and isatan B (indoxyl ketogluconate), together with seed germination ability were compared in Isatis tinctoria and Isatis indigotica grown under six different light conditions (darkness, white, red, far red, blue, yellow light) at 25°C. Light quality influenced both germination and production of indigo precursors in the two Isatis species. Different responsiveness to far red and blue light was observed. Indeed, a detrimental effect on germination by blue and far red light was found in I. tinctoria only. Different amounts of isatan B were produced under red and far red light in the two Isatis species. In I. tinctoria, the level of main indigo precursor isatan B was maximal under red light and minimal under far red light. Whereas in I. indigotica far red light promoted a large accumulation of isatan B. The photon fluence rate dependency for white and yellow light responses showed that the accumulation of indigo precursors was differently influenced in the two Isatis species. In particular, both white and yellow light enhanced above 40 μmol m-2 s-1 the production of isatan B in I. indigotica while only white light showed a photon fluence dependency in I. tinctoria. These results suggest a different role played by the labile and stable phytochrome species (phyA and phyB) in the isatan B production in I. tinctoria and I. indigotica. I. indigotica, whose germination percentage was not influenced by light quality, demonstrated higher germination capability compared with I. tinctoria. In fact, I. tinctoria showed high frequency of germination in darkness and under light sources that establish high phytochrome photoequilibrium (red, white and yellow light). Germination in I. tinctoria was negatively affected by far red and blue light. I. indigotica seeds appear to be indifferent to canopy-like light (far red). Our results provide further insights on the distinct behaviour of I. tinctoria and I. indigotica that belong to two different genetic clusters and different original environments
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