Approaching Veraison---Grapevine Internal Clocks

This past weekend, we visited our friends who have an established vineyard and in walking through their vineyard, observed that the Chardonnay was approaching veraison. I am reading about grapevine phenology in chapter 2 of Markus Keller's textbook on The Science of Grapevines. The definition that he provides in this book was very helpful to me.
Phenology: a definition as it applies to the grapevine
It is the study of the sequence of plant development and is mainly concerned with the timing of specific stages of growth and development in the annual cycle.
Knowing grapevine phenology is helpful for the following reasons:

• Site and cultivar selection
• Vineyard design
• Planning of labor and equipment requirements
• Timing of cultural practices as part of vineyard management

I am familiar with the process call the circadian rhythm, but I didn't know that this is how grapevines monitor the seasons. The vine's circadian rhythm is driven by a self-sustaining oscillator consisting of proteins that oscillate with a 24 hour rhythm in response to light and this is how the plant regulates its physiological functions! Who knew!
Plants are smart enough to compensate for the temperature change as the seasons progress and can reset the phase of the clock. This synchronization of the circadian clock to the external environment is called entrainment. The grapevine's internal clock as well as their hormones are important in the seasonal progress of the grapevine from budbreak to what we ultimately desire, a great harvest.