Skip to main content
PMC home page
Plant Physiology logoLink to Plant Physiology
. 1996 Feb;110(2):439–444. doi: 10.1104/pp.110.2.439

Phytochrome A Mediates the Promotion of Seed Germination by Very Low Fluences of Light and Canopy Shade Light in Arabidopsis.

J F Botto 1, R A Sanchez 1, G C Whitelam 1, J J Casal 1
PMCID: PMC157738  PMID: 12226195

Abstract

Seeds of the wild type (WT) and of the phyA and phyB mutants of Arabidopsis thaliana were exposed to single red light (R)/far-red light (FR) pulses predicted to establish a series of calculated phytochrome photoequilibria (Pfr/P). WT and phyB seeds showed biphasic responses to Pfr/P. The first phase, i.e. the very-low-fluence response (VLFR), occurred below Pfr/P = 10-1%. The second phase, i.e. the low-fluence response, occurred above Pfr/P = 3%. The VLFR was similarly induced by either a FR pulse saturating photoconversion or a subsaturating R pulse predicted to establish the same Pfr/P. The VLFR was absent in phyA seeds, which showed a strong low-fluence response. In the field, even brief exposures to the very low fluences of canopy shade light (R/FR ratio < 0.05) promoted germination above dark controls in WT and phyB seeds but not in the phyA mutant. Seeds of the phyA mutant germinated normally under canopies providing higher R/FR ratios or under deep canopy shade light supplemented with R from light-emitting diodes. We propose that phytochrome A mediates VLFR of A. thaliana seeds.

Full Text

The Full Text of this article is available as a PDF (586.6 KB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Casal J. J. Coupling of phytochrome B to the control of hypocotyl growth in Arabidopsis. Planta. 1995;196(1):23–29. doi: 10.1007/BF00193213. [DOI] [PubMed] [Google Scholar]
  2. Clack T., Mathews S., Sharrock R. A. The phytochrome apoprotein family in Arabidopsis is encoded by five genes: the sequences and expression of PHYD and PHYE. Plant Mol Biol. 1994 Jun;25(3):413–427. doi: 10.1007/BF00043870. [DOI] [PubMed] [Google Scholar]
  3. Johnson E., Bradley M., Harberd N. P., Whitelam G. C. Photoresponses of Light-Grown phyA Mutants of Arabidopsis (Phytochrome A Is Required for the Perception of Daylength Extensions). Plant Physiol. 1994 May;105(1):141–149. doi: 10.1104/pp.105.1.141. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Nagatani A., Reed J. W., Chory J. Isolation and Initial Characterization of Arabidopsis Mutants That Are Deficient in Phytochrome A. Plant Physiol. 1993 May;102(1):269–277. doi: 10.1104/pp.102.1.269. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Parks B. M., Quail P. H. hy8, a new class of arabidopsis long hypocotyl mutants deficient in functional phytochrome A. Plant Cell. 1993 Jan;5(1):39–48. doi: 10.1105/tpc.5.1.39. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Quail P. H., Boylan M. T., Parks B. M., Short T. W., Xu Y., Wagner D. Phytochromes: photosensory perception and signal transduction. Science. 1995 May 5;268(5211):675–680. doi: 10.1126/science.7732376. [DOI] [PubMed] [Google Scholar]
  7. Reed J. W., Nagatani A., Elich T. D., Fagan M., Chory J. Phytochrome A and Phytochrome B Have Overlapping but Distinct Functions in Arabidopsis Development. Plant Physiol. 1994 Apr;104(4):1139–1149. doi: 10.1104/pp.104.4.1139. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Reed J. W., Nagpal P., Poole D. S., Furuya M., Chory J. Mutations in the gene for the red/far-red light receptor phytochrome B alter cell elongation and physiological responses throughout Arabidopsis development. Plant Cell. 1993 Feb;5(2):147–157. doi: 10.1105/tpc.5.2.147. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Rethy R., Dedonder A., De Petter E., Van Wiemeersch L., Fredericq H., De Greef J., Steyaert H., Stevens H. Biphasic fluence-response curves for phytochrome-mediated kalanchoë seed germination : sensitization by gibberellic Acid. Plant Physiol. 1987 Jan;83(1):126–130. doi: 10.1104/pp.83.1.126. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Shinomura T., Nagatani A., Chory J., Furuya M. The Induction of Seed Germination in Arabidopsis thaliana Is Regulated Principally by Phytochrome B and Secondarily by Phytochrome A. Plant Physiol. 1994 Feb;104(2):363–371. doi: 10.1104/pp.104.2.363. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Somers D. E., Sharrock R. A., Tepperman J. M., Quail P. H. The hy3 Long Hypocotyl Mutant of Arabidopsis Is Deficient in Phytochrome B. Plant Cell. 1991 Dec;3(12):1263–1274. doi: 10.1105/tpc.3.12.1263. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Vander Woude W. J., Toole V. K. Studies of the Mechanism of Enhancement of Phytochrome-dependent Lettuce Seed Germination by Prechilling. Plant Physiol. 1980 Aug;66(2):220–224. doi: 10.1104/pp.66.2.220. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Whitelam G. C., Johnson E., Peng J., Carol P., Anderson M. L., Cowl J. S., Harberd N. P. Phytochrome A null mutants of Arabidopsis display a wild-type phenotype in white light. Plant Cell. 1993 Jul;5(7):757–768. doi: 10.1105/tpc.5.7.757. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Plant Physiology are provided here courtesy of Oxford University Press

RESOURCES