Rapid Suppression of Extension Growth in Dark-Grown Wheat Seedlings by Red Light

Abstract— Fluence‐response relationships have been measured at wavelengths from 350 to 760 nm for the enhancement of phototropism in Arabidopsis thulium L. (Heynh) strain “Estland” by an irradiation at each of these wavelengths, given 2 h prior to a 450 nm inductive unilateral irradiation. Action spectra have been constructed from these fluence‐response relationships based on: (i) the fluence required to obtain a curvature of 25° (corresponding to an enhancement of 15°), (ii) the fluence required to obtain 50% of the maximum enhancement and (iii) the fluence threshold for enhancement by a pre‐irradiation. The action spectra exhibit two maxima, one at 669 nm and a second at 378 nm. The height of the maximum at 669 nm is approximately 4 times the height of the maximum at 378 nm. Based on the action spectra, it is concluded that the enhancement of phototropism in A. thaliana is mediated by phytochrome.

Section: Resultssupporting

confidence: 92%

ACTION SPECTRUM FOR ENHANCEMENT OF PHOTOTROPISM BY Arabidopsis thaliana SEEDLINGS

Janoudi

Poff

1992

“…The developmental changes that characterize deetiolation are relatively slow, and the associated gene expression changes also take place over periods of several hours. Other approaches have demonstrated that, at least in some etiolated seedlings, phytochrome-mediated effects on extension growth can be very rapid (Bleiss and Smith, 1985;Smith and Jackson, 1987). Similarly, some cellular processes regulated by phytochrome in etiolated tissues are extremely rapid, taking place within seconds (Quail, 1980).…”

Section: De-etiolation and Seedling Establishmentmentioning

confidence: 99%

The Ecological Functions of the Phytochrome Family. Clues to a Transgenic Programme of Crop Improvement

Smith

1992

Self Cite

Abstract— Phytochrome‐mediated proximity perception and induction of shade avoidance responses provide clues towards a novel genetic engineering approach for the improvement of crop plants. In this Commentary Article, I argue that the elimination, or disablement, of proximity perception and the associated shade avoidance syndrome by transgenic manipulation of phytochrome genes should provide a strategy for the creation of new crop plants in which a greater proportion of assimilates is incorporated into harvestable material. Such a programme would enable increases in agricultural productivity without a requirement for the increased application of agrochemicals. Some potential approaches towards realizing these goals are proposed.

“…Displacement transducers have been used for studying rapid growth responses to light (e.g. Meijer, 1968;Black, 1979, 1983a,b;Morgan et al, 1980;Cosgrove, 1981a;Cosgrove and Green, 1981;Bleiss and Smith, 1985). The method has disadvantages: only a small number of samples can be processed, and there is variability in the magnitude of the measured growth responses.…”

Section: The Use Of the Displacement Transducermentioning

confidence: 99%

Photoreceptor Interaction in Plant Photomorphogenesis: The Limits of Experimental Techniques and Their Interpretations

Gaba

Black

1987

Problems concerning the interpretation of interactions of higher plant photomorphogenetic receptors are discussed. The theory that action of a blue light photoreceptor serves only to maintain responsiveness to phytochrome (Pesponsiveness Theory) is demonstrated to be unable to be properly tested with present techniques. This theory is also unable to explain experimental results any better than an alternative theory that a blue light photoreceptor may require the presence of the active form of phytochrome to express its activity (Presence Theory). This latter theory is also incapable of being fully tested. There does not appear to be an adequate current theory to explain photoreceptor interactions. Other issues discussed include the use of displacement transducers in growth studies, the induction of phytochrome-type responses by blue light, and the relative importance of the photoreceptors. New data are introduced on the effect of blue light in the end-of-day growth response to phytochrome of the lightgrown Cucumis sativus L. hypocotyl, and on the light equivalence principle in the same species.