Jun 28, 2023

How do plants keep track of the seasons of the year and the time of day?

#flowering #flower #plantflowers Circadian rhythm, plant body clock

As spring progresses into summer, summer into fall, and fall into winter, wildflowers bloom at their appointed times.

The transition to flowering involves major changes in the pattern of morphogenesis and cell differentiation at the shoot apical meristem. Ultimately this process leads to the production of floral organs—sepals, petals, stamens, and carpels.
Organisms are normally subjected to daily cycles of light and darkness, and both plants and animals often exhibit rhythmic behavior in association with these changes.
Examples of such rhythms include leaf and petal movements (day and night positions), stomatal opening and closing, growth and sporulation patterns in fungi (e.g., Pilobolus and Neurospora), time of day of pupal emergence (the fruit fly Drosophila), and activity cycles in rodents, as well as metabolic processes such as photosynthetic capacity and respiration rate.

"Our research shows that sugar levels within a plant play a vital role in synchronizing circadian rhythms with its surrounding environment."

-Alex Webb

The circadian rhythm, a 24-hour "body clock," is present in both plants and animals. Plants have an inbuilt ability to measure time, even in the absence of light, thanks to their biological timer; they don't just react to sunrise, for instance; they anticipate it and change their biology appropriately.

This capacity to keep time is crucial for biological activities including blooming, scent release, and leaf movement, and offers a significant competitive advantage.
Plants produce sugar via photosynthesis; it is their way of converting the sun’s energy into a usable chemical form needed for growth and function.
The effects of these sugars by monitoring seedlings in CO2-free air, inhibiting photosynthesis, growing genetically altered plants, and monitoring their biology. The production of sugars was found to regulate key genes responsible for the 24-hour rhythm.
These circadian rhythms cannot be direct responses to the presence or absence of light but must be based on an internal pacemaker, often called an endogenous oscillator.
It is coupled to a variety of physiological processes, such as leaf movement or photosynthesis, and it maintains the rhythm. For this reason, it can be considered the clock mechanism, and the physiological functions that are being regulated, such as leaf movements or photosynthesis, are sometimes referred to as the hands of the clock.

Circadian rhythms arise from cyclic phenomena that are defined by three parameters:

Period, the interval between similar points in a recurrent cycle. The time between two successive maxima (peaks) or minima (troughs) is commonly used to quantify the period.
Phase is any point in the cycle that is recognizable by its relationship to the rest of the cycle. The most obvious phase points are the peak and trough positions.
Amplitude is usually considered to be the distance between peak and trough. The amplitude of a biological rhythm can often vary while the period remains unchanged.

In constant light or darkness, rhythms depart from an exact 24-hour period. The rhythms then drift in relation to solar time, either gaining or losing time depending on whether the period is shorter or longer than 24 hours.