Jul 2, 2023

Which environmental signals control flowering, and how are those signals perceived?

Cells communicate constantly with one another in both plants and mammals.

The photoperiod and temperature/ vernalization pathways mainly perceive external signals from the environment, while the autonomous and age pathways transmit endogenous cues within plants.

In order to respond to the varying levels of light, darkness, and temperature that direct the plant's cycle of development, blooming, and fruiting, plant cells interact with one another.
Plant cells also communicate to coordinate what goes on in their roots, stems, and leaves.
Although plants and animals are eukaryotes, they have had separate evolutionary histories for over a billion years.
Nitric oxide and Ca2+ are widely used for signaling in both plants and animals.

Under natural conditions, the endogenous oscillator is entrained (synchronized) to a true 24-hour period by environmental signals, the most important of which are the light-to-dark transition at dusk and the dark-to-light transition at dawn.

Such environmental signals are termed zeitgebers (German for “time givers”). When such signals are removed— for example, by transfer to continuous darkness—the rhythm is said to be free-running, and it reverts to the circadian period that is characteristic of the particular organism.
Although the rhythms are internally created, they typically need an external cue to begin manifesting, such as exposure to light or a change in temperature.
Additionally, when an organism is exposed to a consistent environment for a while, many rhythms get dampened and must be resumed by an environmental zeitgeber, such as the transition from light to dark or a change in temperature.
The circadian clock would be of no value to the organism if it could not keep accurate time under the fluctuating temperatures experienced in natural conditions.
In fact, the temperature has little to no impact on the free running rhythm's period. Temperature compensation is the term for the function that allows the clock to maintain time at various temperatures.

Although all of the biochemical steps in the pathway are temperature-sensitive, their temperature responses probably cancel each other.

For instance, adjustments to the rates of degradation of intermediates might be made in conjunction with adjustments to the rates of synthesis. In this manner, the clock regulators' steady-state values would be constant at various temperatures.