Coleoptile phototropic response

There is growing evidence that zeaxanthin present in the photosynthetic apparatus is functional also as a photoreceptor for stomata opening and coleoptile phototropic response (Zeiger and Zhu,... 

Quinones MA, Lu Z and Zeiger E (1996) Close correspondence between the action spectra for the blue light responses of the guard cell and coleoptile chloroplasts, and the spectra for blue hght-dependent stomatal opening and coleoptile phototropism. Proc Natl Acad Sci USA 93 2224-2228... 

Briggs WR (1963) Red light, auxin relationships and the phototropic responses of corn and oat coleoptiles. Am J Bot 50 196-207... 

A preirradiation with a strong pulse of blue light desensitizes transiently Avena coleoptiles and causes a shift of the entire bell-shaped fluence-response curve for fPlPP. In Zea coleoptiles, preirradiation reduces mainly the phototropic responsivity, not however, the absolute threshold. After about 120 min in darkness, the responsivity recovers, and the original bell-shaped curve for the fPIPP is reestablished, indicating that the full sensitivity has recovered. "- Earlier authors who worked with a sequence of strong conditioning pulses and subsequent unilateral pulses of lesser irradiance similarly found evidence for... 

Blaauw, O.H. and Blaauw-Jansen, G., The phototropic responses of Avena coleoptiles, Acta Bot. Neerl, 19, 755, 1970. 

Neumann, R. and lino, M., Phototropism of rice (Oryza sativa L.) coleoptiles fluence-response relationships, kinetics and photogravitropic equihbrium, Planta, 201, 288,1997. 

Fig. 2. Phototropic dosage response curves for oat coleoptiles at three intensities of blue light (440 nm) (7) 1.4 10-11, (2)...

Fig. 15. Specific chemical inhibition of physiological bluelight responses 04) Swimming, inverse phobic response and direct photophobic response of Euglena as a function of iodide concentration118. (B) Phototropic and geotropic curvature of the avena coleoptile as function of azide concentration1S41...

Fig. 22. (A) Comparison of flavin triplet -> triplet absorption spectra (downwards drawn) with bluelight-induced (440 nm) phototropic curvature of aVena coleoptiles as inhibited by strong monochromatic light in the long wave visible region 154). (B) Comparison of the growth response of Phycomyces induced by strong laser light of wavelength longer than 590nm46, with the flavin phosphorescence spectrum los)...

Pickard BG, Thimann KV (1964) Transport and distribution of auxin during tropistic response. II. The lateral migration of auxin in phototropism of coleoptiles. Plant Physiol 39 341-350... 

FIGURE 132.1 Photon fluence-response curves for phototropic bending of Avena coleoptiles. (A) Coleoptiles were irradiated unilaterally with a blue-light pulse (458 nm) of constant duration (30 s) and variable photon-fluence rates. (B) Irradiation with constant photon-fluence rates (0.01,0.1, and 1 pmol s ) and variable pulse duration. Bending angles were measured 2 h after the unilateral light pulse. 

Numerous phototropic organisms display fluence-response relationships that are similar to those of grass coleoptiles. These include various monocots and dicots, Phycomyces, Pilobolus, Arabidopsis, Vauche-ria, and chloronemata of the fern Dryopteris. " ° The fluence-response curves for the phototropism of Raphanus seedlings appear less typical in that a classical bell-shaped curve for the first positive phototropism is absent. Kinetic models for the complex dose-response relationships were proposed by several authors. ... 

---