Abstract
The herbicide, 4 chloro-5-(methylamino)-2-(α,α,α,-trifluoro-m-tolyl)-3 (2H)-pyridazinone (SAN 9789), which blocks the synthesis in higher plants of colored carotenoids but not of flavins, was used to examine the involvement of carotenoids in corn seedling phototropism. It was concluded that “bulk” carotenoids are not the photoreceptor pigment based on the results that increasing concentrations of SAN 9789 (up to 100 micromolar) did not alter the phototropic sensitivity to 380 nanometers light (using geotropism as a control) and did not increase the threshold intensities of fluence response curves for both 380 and 450 nanometers light even though carotenoid content was reduced to 1 to 2% of normal. SAN 9789 treatment, however, did reduce seedling sensitivity toward 450 nanometers light indicating that carotenoids are involved in phototropism. Carotenoids, which are located mainly in the primary leaves, may act in phototropism as an internal screen, enhancing the light intensity gradient across the seedling and thus contributing to the ability of the seedling to perceive light direction. These results indicate that the action spectra for phototropic responses can be significantly affected by the absorbance of screening pigments in vivo thus altering its shape from the in vitro absorption spectrum of the photoreceptor pigment.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bartels P. G., McCullough C. A new inhibitor of carotenoid synthesis in higher plants: 4-chloro-5-(dimethylamino)-2- , , ,(trifluoro-m-tolyl)-3(2H)-pyridazinone. Biochem Biophys Res Commun. 1972 Jul 11;48(1):16–22. doi: 10.1016/0006-291x(72)90337-3. [DOI] [PubMed] [Google Scholar]
- Butler W. L. Absorption spectroscopy of biological materials. Methods Enzymol. 1972;24:3–25. doi: 10.1016/0076-6879(72)24052-6. [DOI] [PubMed] [Google Scholar]
- Checcucci A., Colombetti G., Ferrara R., Lenci F. Action spectra for photoaccumulation of green and colorless Euglena: evidence for identification of receptor pigments. Photochem Photobiol. 1976 Jan;23(1):51–54. doi: 10.1111/j.1751-1097.1976.tb06770.x. [DOI] [PubMed] [Google Scholar]
- Davis K. A., Hatefi Y., Poff K. L., Butler W. L. The b-type cytochromes of bovine heart mitochondria: absorption spectra, enzymatic properties, and distribution in the electron transfer complexes. Biochim Biophys Acta. 1973 Dec 14;325(3):341–356. doi: 10.1016/0005-2728(73)90196-5. [DOI] [PubMed] [Google Scholar]
- Delbrück M., Shropshire W. Action and Transmission Spectra of Phycomyces. Plant Physiol. 1960 Mar;35(2):194–204. doi: 10.1104/pp.35.2.194. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Everett M., Thimann K. V. Second positive phototropism in the Avena coleoptile. Plant Physiol. 1968 Nov;43(11):1786–1792. doi: 10.1104/pp.43.11.1786. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jabben M., Deitzer G. F. Effects of the herbicide san 9789 on photomorphogenic responses. Plant Physiol. 1979 Mar;63(3):481–485. doi: 10.1104/pp.63.3.481. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jesaitis A. J., Heners P. R., Hertel R. Characterization of a Membrane Fraction Containing a b-type Cytochrome. Plant Physiol. 1977 May;59(5):941–947. doi: 10.1104/pp.59.5.941. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sargent M. L., Briggs W. R. The effects of light on a circadian rhythm of conidiation in neurospora. Plant Physiol. 1967 Nov;42(11):1504–1510. doi: 10.1104/pp.42.11.1504. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Schmidt W., Hart J., Filner P., Poff K. L. Specific inhibition of phototropism in corn seedlings. Plant Physiol. 1977 Nov;60(5):736–738. doi: 10.1104/pp.60.5.736. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wald G., Du Buy H. G. PIGMENTS OF THE OAT COLEOPTILE. Science. 1936 Sep 11;84(2176):247–247. doi: 10.1126/science.84.2176.247-a. [DOI] [PubMed] [Google Scholar]