No smartphone, no problem: Plants have their own built-in 'Season-Meter'

Plants possess a built-in mechanism known as the "Season-Meter" that allows them to predict seasonal changes and determine the optimal time for growth, flowering, and other activities. Researchers from the University of Tsukuba investigated this system across two wild perennial plant species native to Japan: wasabi and A. halleri.

By analyzing the activity of three genes over a two-year period, the scientists discovered that each gene operates on a different timescale, ranging from a few days to nearly five months. These genes collectively enable plants to forecast all four seasons of the year. The presence of the Season-Meter, an internal memory system, allows plants to prepare ahead of time rather than reacting solely to current weather conditions.

This internal clock responds to past temperatures through epigenetic changes in chromatin, rather than relying on the day's temperature alone. Previous knowledge suggested that plants retain a memory of past temperatures, but there was no established method to quantify the extent of this memory or its consistency across species.

The study focused on the two studied species, tracking the three genes involved in the Season-Meter over consecutive years. The researchers found that the genes integrated past temperatures using different time scales, with one gene recalling temperatures from only a few days, another from a few weeks, and the third from nearly five months.

The combined activity of these three genes allowed plants to track seasonal progression consistently throughout the year. This seasonal forecasting method, based solely on past temperature data, successfully predicted gene behavior in an independent year, demonstrating the reproducibility and reliability of the epigenetic temperature-memory system.

The findings suggest that this universal strategy is applicable across diverse plant species, offering a useful tool for predicting plant responses to climate change.