Phototropic response

In analogy to the experiments described above one obtains that the delay of a phototropic response will increase with increasing I/I0. The delay as a function of the stimulatory light intensity is given in Fig. 9. 

All formal models of phototropism try to determine two main points (i) is it possible to predict the phototropic response knowing the light-growth response (ii) if so, how is it that in the light-growth response the growth rate returns to the baseline level after 20 min while the phototropic response is constant for hours ... 

The normal phototropic response of (3-caroteneless mutants with no trace amounts of carotene (Presti et al., 1977) is in apparent contrast to the deficiency exhibited by the same mutants in photophorogenesis. A clear relationship between (3-carotene concentration and visual threshold for photophorogenesis could be established. However arguments have been presented indicating the unlikelihood that (3-carotene is the only photoreceptor in photophorogenesis (Galland and Russo, 1979a, in press). 

While receptors for visible light are very common in marine species, less is known about the detection of UV. In aquatic invertebrates, UV photoreception is primarily in the UVA wavelengths, although variable UVB phototropic responses have been observed.36 38 Visual UV photosensitivity is a specific characteristic in some animal species, including arthropods, reptiles, fish, birds, and... 

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,... 

Another compound with plant hormone-like activity is raphanusanin, a natural inhibitor of radish hypocotyl elongation which is believed to be instrumental in its phototropic response [179]. Raphanusanin has been reported to prevent auxin-induced MT reorientations [19]. However, there is no direct evidence that raphanusanin exerts an effect on MTs. 

Figure 142 Characteristic phototropic response of Psilocybe cubensis toward light.

Plants also contain calmodulin, and they employ Ca as a second messenger. (cAMP is not a second messenger in plants.) Both gravitropic and phototropic responses in plants appear to depend on Ca. ... 

Carotenoids mediate phototropic responses in higher plants and fungi (E 2.2). They are flower pigments attracting pollinators (E 5.5.1) and strengthen membrane rigidity in microorganisms and plants (E 2.2). 

Helianthus annuus L. The phototropic response of the green sunflower hypocotyl is a local phenomenon apex and cotyledons can be covered or even removed... 

Photo-oxidation of auxin by light is important to plants since at least part of the phototropic response seems linked to an auxin destroying mechanism. However, the in situ nature of this process is far from certain. The action spectra of the most sensitive phototropic responses in both higher plants and fungi are remarkably similar, with maxima in the blue, but whether the... 

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

Gordon SA, Eib M (1956) Auxin transport in the phototropic response (abstract). Plant Physiol Suppl 31 XIV... 

Auxins are well-known plant growth hormones involved in plant processes including embryogenesis, apical patterning, stem elongation, development of vascular tissues, and root initiations that mediate gravitropic and phototropic responses in... 

Holmes, M.G. and Keiler, D.R., A novel phototropic response to supplementary ultraviolet (UV-B and UV-A) radiation in the sihquas of oilseed rape Brassica napus L.) grown under natural conditions, Photochem. Photobiol. Sci., 1, 890, 2002. 

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