This paper is part of the contributions to the European Symposium Photomorphogenesis in Plantsheld in Tirrenia, Pisa, Italy, 11–15 July, 1993.
Impaired stem-growth responses to blue-light irradiance in light-grown transgenic tobacco seedlings overexpressing Avena phytochrome A
Article first published online: 28 APR 2006
Volume 91, Issue 2, pages 268–272, June 1994
How to Cite
Casal, J.J. and Sánchez, R.A. (1994), Impaired stem-growth responses to blue-light irradiance in light-grown transgenic tobacco seedlings overexpressing Avena phytochrome A. Physiologia Plantarum, 91: 268–272. doi: 10.1111/j.1399-3054.1994.tb00429.x
- Issue published online: 28 APR 2006
- Article first published online: 28 APR 2006
- Received 10 August, 1993; revised 10 December, 1993
- Blue light;
- Nicotiana tabaccum;
- stem growth;
- transgenic plants
The effects of blue light (B) on stem extension-growth were compared in light-grown seedlings, of tobacco overexpressing Avena phytochrome A and its isogenic wild type (WT). Under natural radiation, lowering the levels of B reaching the whole shoot promoted stem extension growth in WT but not in transgenic seedlings. Under controlled conditions, the seedlings were exposed to white light (WL) or WL minus B, each one provided at two different irradiances. In WT seedlings stem extension growth was promoted by lowering B at both irradiance levels. In transgenic seedlings a reduction of B was promotive only at low irradiance levels. The seedlings were also grown under WL, WL minus B, WL minus red light (R) and far-red light (FR) or WL minus R, FR and B. In the WT, lowering B promoted stem extension growth irrespective of R+FR levels. In the transgenics, B was effective only at very low levels of R+FR (i.e. at low phytochrome cycling rates). Lowering the Pfr levels at the end of the day promoted extension growth in wild type and transgenic seedlings. Responses to B were not observed in transgenic seedlings having low Pfr levels at the end of the day. The results suggest that the overexpressed phytochrome A acts mainly via irradiance-dependent reactions. When these reactions are highly expressed, B responses are not observed.