Regulation of growth by light. Spektrofotometrichesky definition of phytochrome

you are: Regulation of growth by light

For definition of the maintenance of phytochrome in a vegetative fabric it is possible to use two-wave spektrofotometr.

1. To a ditch fill with slices of a vegetative fabric (or an extract from them) and irradiate with red light (660 nanometers) high intensity. About minute actinic irradiations it is enough for limiting degree of transformation of Fk in Fdk.

2. Absorption (named also by optical density (OP), measure alternately at 660, 730, 660 nanometers etc. The measuring bunch has small intensity, and each irradiation is so short-term that does not cause considerable transformation of a pigment.

[OP at 660 nanometers - OP at 730 nanometers] after an irradiation actinic light with length of a wave 660 designate АОП660-

3. Then the fabric in a ditch is irradiated with distant red light {with 730 nanometers) high intensity. Duration of an actinic irradiation should be sufficient for limiting degree of transformation of Fdk in Fk.

4. Repeat a stage 2.

[OP at 660 nanometers - OP at 730 nanometers] after an irradiation aktinich th light designate АОП730.

5. АОП660-ДОП730=А (AOP) there is a measure of the maintenance of phyto-chrome in a vegetative fabric.

From fig. 11.9 it is visible, as Fk, and Fdk have wide spectra of absorption which are blocked in red and distant red areas (660-730 nanometers) and in dark blue area (400-460 nanometers). Therefore any radiation in these sites of a spectrum transforms any part of phytochrome into the form of Fda. Red light with length of a wave 660 nanometers is most effective and forms 75% of Fda while distant red light with length of a wave 730 nanometers is least effective and gives only 2% of Fdk. Lengths of waves between 600 both 730 nanometers and dark blue light possess intermediate efficiency.

As in the fabric which have been grown up in the dark, all phytochrome is presented in the form of Fk, actually any irradiation raises level of Fdk. The exception makes green light with length of a wave 500-550 nanometers as neither Fk, nor Fdk essentially do not absorb these beams. Therefore in experiences with phytochrome green light use as ' safe '.

Prevrashchenija Fkch=Fdk operate as the metabolic mechanism which is switching on and off certain reactions. This switching indirectly regulates set of biophysical, biochemical, histologic and morphological processes in plants (fig. 11.11). Many of coming changes occur after the first influence of light on etiolirovannyj a sprout when some part of its phytochrome passes in the form of Fdk. These changes, obobshchenno named deetioljatsiej, help a plant to adapt for light. Activity of many enzymes and the maintenance of vegetative hormones thus changes, from etioplastov develop hloroplasta, there is a chlorophyll synthesis, karotinoidov and antotsianovyh pigments from predecessors. After pozelenenija etiolirovannyh sprouts the system fitohromov continues to influence growth and development of a plant during all his life. Interconversions of Fk and Fdk not only influence an induction of flowering at plants both short, and long day, but also participate also in regulation klubneobrazovanija, rest, subsidence of leaves and ageing. However the effect of transformations of phytochrome in the plants which have grown on light, depends also on time of influence of light. Sensitivity of such plants to certain forms of phytochrome has rhythmic character. This interesting problem will be considered in the following chapter.