Abstract
The relationship between the amount of light and the amount of response for any photobiological process can be based on the number of incident quanta per unit time (fluence rate-response) or on the number of incident quanta during a given period of irradiation (fluence-response). Fluence-response and fluence rate-response relationships have been measured for second positive phototropism by seedlings of Arabidopsis thaliana. The fluence-response relationships exhibit a single limiting threshold at about 0.01 micromole per square meter when measured at fluence rates from 2.4 × 10−5 to 6.5 × 10−3 micromoles per square meter per second. The threshold values in the fluence rateresponse curves decrease with increasing time of irradiation, but show a common fluence threshold at about 0.01 micromole per square meter. These thresholds are the same as the threshold of about 0.01 micromole per square meter measured for first positive phototropism. Based on these data, it is suggested that second positive curvature has a threshold in time of about 10 minutes. Moreover, if the times of irradiation exceed the time threshold, there is a single limiting fluence threshold at about 0.01 micromole per square meter. Thus, the limiting fluence threshold for second positive phototropism is the same as the fluence threshold for first positive phototropism. Based on these data, we suggest that this common fluence threshold for first positive and second positive phototropism is set by a single photoreceptor pigment system.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Briggs W. R. Light Dosage and Phototropic Responses of Corn and Oat Coleoptiles. Plant Physiol. 1960 Nov;35(6):951–962. doi: 10.1104/pp.35.6.951. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Briggs W. R. Mediation of Phototropic Responses of Corn Coleoptiles by Lateral Transport of Auxin. Plant Physiol. 1963 May;38(3):237–247. doi: 10.1104/pp.38.3.237. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Iino M. Pulse-induced phototropisms in oat and maize coleoptiles. Plant Physiol. 1988 Nov;88(3):823–828. doi: 10.1104/pp.88.3.823. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Khurana J. P., Poff K. L. Mutants of Arabidopsis thaliana with altered phototropism. Planta. 1989;178:400–406. [PubMed] [Google Scholar]
- Khurana J. P., Ren Z., Steinitz B., Parks B., Best T. R., Poff K. L. Mutants of Arabidopsis thaliana with decreased amplitude in their phototropic response. Plant Physiol. 1989;91:685–689. doi: 10.1104/pp.91.2.685. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Konjević R., Steinitz B., Poff K. L. Dependence of the phototropic response of Arabidopsis thaliana on fluence rate and wavelength. Proc Natl Acad Sci U S A. 1989 Dec;86(24):9876–9880. doi: 10.1073/pnas.86.24.9876. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Steinitz B., Ren Z., Poff K. L. Blue and Green Light-Induced Phototropism in Arabidopsis thaliana and Lactuca sativa L. Seedlings. Plant Physiol. 1985 Jan;77(1):248–251. doi: 10.1104/pp.77.1.248. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Zimmerman B. K., Briggs W. R. A Kinetic Model for Phototropic Responses of Oat Coleoptiles. Plant Physiol. 1963 May;38(3):253–261. doi: 10.1104/pp.38.3.253. [DOI] [PMC free article] [PubMed] [Google Scholar]