Circadian rhythms of flower induction and their significance in photoperiodic response

1969 ◽  
Vol 47 (2) ◽  
pp. 309-324 ◽  
Author(s):  
Bruce G. Cumming
Keyword(s):  
Active Form ◽  
Photoperiodic Response ◽  
Endogenous Rhythm ◽  
Flower Induction ◽  
Primary Control ◽  
Endogenous Rhythms ◽  
Free Running ◽  
System 1 ◽  
And Control ◽  
Measurement And Control

Endogenous rhythms of flower induction in Chenopodium rubrum provide at least a partial basis for time measurement and control of flower induction in daily light: dark (photoperiodic) cycles. The results support Bünning's hypothesis of the physiological clock.The following three intrinsic components can exert a primary control in both the endogenous free-running and the externally forced system.(1) GenotypeThe endogenous rhythmic flowering responses of different latitudinal ecotypes show specific characteristics that are also expressed in daily photoperiodic cycles.(2) PhytochromeChanges in the level of Pfr (the active form of phytochrome) cause shifts in endogenous phase and photoperiodic optima that are qualitatively similar. Changes in Pfr level have effects on flower induction that are similar in both the photophile phase of an endogenous rhythm and in the light period of inductive daily photoperiodic cycles—just as the effects obtained in the transduction (skotophile) phase of the endogenous rhythm are similar to those obtained in the dark period of daily photoperiodic cycles.(3) Photosynthetic Energy MetabolismThe effects on flower induction obtained by changing light intensity and (or) quality, and by applying sugars, suggest that there is a greater utilization and (or) availability of substrates (arising from carbohydrate metabolism and involved in Pfr pacemaker effects) in the photophile than in the transduction phases of prolonged darkness. This appears to reflect the sequence that would normally be imposed in daily photoperiodic cycles.A basis for the overt relationships between endogenous rhythmic and photoperiodic response could exist if there are endogenous oscillations in energy metabolites derived from photosynthesis. Such a system could have become selectively evolved as an adaptive response to natural alternations of light and darkness. Demultiplication of higher frequency oscillations may be a significant adaptive mechanism in circadian timing of flower induction.

2. Measurement and Control of Airborne Microorganisms Using Electrostatic Methods

2001 ◽  
Author(s):  
G. Mainelis ◽  
R. Gorny ◽  
K. Willeke ◽  
S. Grinshpun ◽  
T. Reponen ◽  
...  
Keyword(s):  
Airborne Microorganisms ◽  
And Control ◽  
Measurement And Control

Analysis of the horizontal structure of a measurement and control geodetic network based on entropy

2013 ◽  
Vol 62 (1) ◽  
pp. 23-31 ◽  
Author(s):  
Maria Mrówczyńska
Keyword(s):  
Geodetic Network ◽  
The State ◽  
Observation System ◽  
Optimum Number ◽  
Optimum Structure ◽  
Horizontal Structure ◽  
The Difference ◽  
And Control ◽  
Measurement And Control ◽  
Horizontal Displacements

Abstract The paper attempts to determine an optimum structure of a directional measurement and control network intended for investigating horizontal displacements. For this purpose it uses the notion of entropy as a logarithmical measure of probability of the state of a particular observation system. An optimum number of observations results from the difference of the entropy of the vector of parameters ΔHX̂ (x)corresponding to one extra observation. An increment of entropy interpreted as an increment of the amount of information about the state of the system determines the adoption or rejection of another extra observation to be carried out.

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