Tsirkadnye rhythms. Interaction of phytochrome with internal clocks

you are: Tsirkadnye rhythms

We are obliged by the Considerable part of our knowledge of internal clocks to a sharp insight and carefully executed experiences of German physiologist Ervina Bjunninga. Observing over 10 grades of a soya, he has noticed accurate correlation between their photoperiodic reaction and sleepy movements of leaves. therefore he has assumed that both processes are regulated by the same inner clock. From set of the grades of the form studied by it with the most expressed sheet movements there were obligatnymi korotkodnevnymi plants concerning flowering, and the others - mostly neutral. Apparently, the same defined fitohromami rhythmic reactions which operate movements of leaves, regulate also photoperiodic processes. On the last depends, what share of resources of a plant will go on vegetative growth, reproduction, creation of reserves and the processes conducting to rest. As sheet movements are less difficult, than the photoperiodic phenomena, studied them to approach to the analysis of interactions of phytochrome with hours.

At niktinastii movements of leaves are caused by changes in volume of motor cages of a sheet small pillow - the body which is at the basis of a sheet plate (fig. 12.8). When leaves are opened, the motor cages located on one party of a sheet small pillow, are in the bulked up condition, and on an opposite side - in compressed. When leaves are combined, the return picture (fig. 12.9) is observed. Changes in volume of motor cages are in turn regulated by mass moving of ions To + and С1- in vakuoli and from vakuolej. Concentration increase To + and С1- reduces water potential of a cage that conducts to the strengthened absorption of water and swelling, and decrease in concentration of these ions - to opposite effect. Redistribution To + and С1-, apparently, is regulated by changes in membranes of motor cages.

At niktinastichnogo the fluctuation phase can be changed plants Samanea which leaves in long darkness make fluctuations with okolosutochnoj periodicity, by change of level of Fdk. The quantity of phytochrome in the form of Fdk, in the beginning defined by spectral structure of light preceding darkness, gradually decreases in process of its transformation into Fk. If the darkness period to interrupt with the short-term influence of red light transforming Fk back in Fdk, the behaviour of the leaves irradiated and not irradiated (control) will be essential to differ.

For example, if leaves to irradiate with red light while they have revealed approximately on half of maximum corner, they will start to develop prematurely while control still continue to reveal. However, if influence by red light occurs on 12 ch later when leaves develop, its effect will be rather small. Thus, transformation of Fk into Fdk in certain phases of a cycle ' translates ' hours whereas during other time it remains ineffectual.

It is possible to explain These interactions, having assumed, as phytochrome, and hours change properties of the same membranes. According to this theory, slow tsirkadiannye changes in permeability and transport properties of cellular membranes occur throughout each daily cycle and are - a part of hours whereas transformations of Fk=Fdk lead to faster changes in structure and function of membranes. Thus, we can see, how phytochrome transformations could ' translate ' hours, changing a condition of cellular membranes. This hypothesis would explain also the time relations influencing ability of flashes of red light to change a course of hours as the effect of transformation of phytochrome would depend then on a condition of a membrane at the moment of light influence. This explanation seems reasonable and logical, but we need to know much more about phytochrome and about hours to estimate, how much it is true.