Ms Gabriele Lenk died on 7 May 2004.
Tomato seed germination: regulation of different response modes by phytochrome B2 and phytochrome A
Article first published online: 1 DEC 2005
Plant, Cell & Environment
Volume 29, Issue 4, pages 701–709, April 2006
How to Cite
APPENROTH, K.-J., LENK, G., GOLDAU, L. and SHARMA, R. (2006), Tomato seed germination: regulation of different response modes by phytochrome B2 and phytochrome A. Plant, Cell & Environment, 29: 701–709. doi: 10.1111/j.1365-3040.2005.01455.x
- Issue published online: 1 DEC 2005
- Article first published online: 1 DEC 2005
- Received 6 September 2005; received in revised form 15 September 2005; accepted for publication 3 October 2005
- Lycopersicon esculentum;
- low fluence response.
Lycopersicon esculentum seeds germinate after rehydration in complete darkness. This response was inhibited by a far-red light (FR) pulse, and the inhibition was reversed by a red light (R) pulse. Comparison of germination in phytochrome-deficient mutants (phyA, phyB1, phyB2, phyAB1, phyB1B2 and phyAB1B2) showed that phytochrome B2 (PhyB2) mediates both responses. The germination was inhibited by strong continuous R (38 µmol m−2 s−1), whereas weak R (28 nmol m−2 s−1) stimulated seed germination. Hourly applied R pulses of the same photon fluence partially replaced the effect of strong continuous R. This response was called ‘antagonistic’ because it counteracts the low fluence response (LFR) induced by a single R pulse. This antagonistic response might be an adaptation to a situation where the seeds sit on the soil surface in full sunlight (adverse for germination), while weak R might reflect that situation under a layer of soil. Unexpectedly, the effects of continuous R or repeated R pulses were mediated by phytochrome A (PhyA). We therefore suggest that low levels of PhyA in its FR-absorbing form (Pfr) cause inhibition of seed germination produced either by extended R irradiation (by degradation of PhyA-Pfr) or by extended FR irradiation [keeping a low Pfr/R-absorbing form (Pr) ratio].