Abstract
Cytokinin replaces light in several aspects of the photomorphogenesis of dicot seedlings. Arabidopsis thaliana seedlings grown under red light have been shown to become disoriented, losing the negative hypocotyl gravitropism that has been observed in seedlings grown in darkness or white light. We report here that cytokinin at micromolar concentrations restores gravitropism to seedlings grown under red light. Cytokinin cancels the effect of red light on the gravity-sensing system and at the same time replaces light in the inhibition of hypocotyl elongation. Furthermore, application of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid acts similarly to cytokinin. Cytokinin cannot restore gravitropism under red light to an ethylene-insensitive mutant that is defective at the EIN2 locus. Stimulation of ethylene production, therefore, can explain the action of cytokinin in restoring negative gravitropism to the hypocotyls of Arabidopsis seedlings grown under continuous red light.
Full Text
The Full Text of this article is available as a PDF (834.3 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Cohen L., Gepstein S., Horwitz B. A. Similarity between Cytokinin and Blue Light Inhibition of Cucumber Hypocotyl Elongation. Plant Physiol. 1991 Jan;95(1):77–81. doi: 10.1104/pp.95.1.77. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Feldman L. J., Briggs W. R. Light-regulated gravitropism in seedling roots of maize. Plant Physiol. 1987;83:241–243. doi: 10.1104/pp.83.2.241. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Fukaki H., Fujisawa H., Tasaka M. SGR1, SGR2, SGR3: novel genetic loci involved in shoot gravitropism in Arabidopsis thaliana. Plant Physiol. 1996 Mar;110(3):945–955. doi: 10.1104/pp.110.3.945. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gepstein S., Thimann K. V. The role of ethylene in the senescence of oat leaves. Plant Physiol. 1981 Aug;68(2):349–354. doi: 10.1104/pp.68.2.349. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jiao X. Z., Yip W. K., Yang S. F. The effect of light and phytochrome on 1-aminocyclopropane-1-carboxylic Acid metabolism in etiolated wheat seedling leaves. Plant Physiol. 1987 Nov;85(3):643–647. doi: 10.1104/pp.85.3.643. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Laskowski M. J., Seradge E., Shinkle J. R., Briggs W. R. Ethylene is not involved in the blue light-induced growth inhibition of red light-grown peas. Plant Physiol. 1992 Sep;100(1):95–99. doi: 10.1104/pp.100.1.95. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Liscum E., Hangarter R. P. Genetic Evidence That the Red-Absorbing Form of Phytochrome B Modulates Gravitropism in Arabidopsis thaliana. Plant Physiol. 1993 Sep;103(1):15–19. doi: 10.1104/pp.103.1.15. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Philosoph-Hadas S., Meir S., Rosenberger I., Halevy A. H. Regulation of the gravitropic response and ethylene biosynthesis in gravistimulated snapdragon spikes by calcium chelators and ethylene inhibitors. Plant Physiol. 1996 Jan;110(1):301–310. doi: 10.1104/pp.110.1.301. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Roman G., Lubarsky B., Kieber J. J., Rothenberg M., Ecker J. R. Genetic analysis of ethylene signal transduction in Arabidopsis thaliana: five novel mutant loci integrated into a stress response pathway. Genetics. 1995 Mar;139(3):1393–1409. doi: 10.1093/genetics/139.3.1393. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Su W., Howell S. H. The Effects of Cytokinin and Light on Hypocotyl Elongation in Arabidopsis Seedlings Are Independent and Additive. Plant Physiol. 1995 Aug;108(4):1423–1430. doi: 10.1104/pp.108.4.1423. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Zobel R. W. Some Physiological Characteristics of the Ethylene-requiring Tomato Mutant Diageotropica. Plant Physiol. 1973 Oct;52(4):385–389. doi: 10.1104/pp.52.4.385. [DOI] [PMC free article] [PubMed] [Google Scholar]