In 1901, Jagdish Chandra Bose had proposed the idea that plants are alive and can experience sensations. Since then, scientists have come a long way in figuring out how plants react to external stimuli.
In new research published in Nature Plants in March, scientists have found that the summer solstice has a profound effect on the lives of plants–especially in the reproduction process of the European beech trees. This finding highlights the intricate connections between celestial events and biological processes.
The reproduction of the European beech trees follows a unique process called masting— perennial plants, particularly trees, produce an exceptionally large number of seeds at irregular intervals. This mass seed production can have profound effects on ecosystem dynamics.
What is unique about European beech trees, is that these trees manage to synchronise masting across 1,500 km with varying geographical and climatic conditions. In other words, European beech trees seem to be dropping their seeds at the same time (triggered by the summer solstice) across Europe.
The study revealed that the summer solstice, occurring on June 21st, acts as a “starting gun” for the synchronised reproductive efforts of beech trees. But how do the trees ‘know’ when to drop their seeds?
Researchers have found that once the days start to shorten post-solstice, the temperature-sensing window opens simultaneously across Europe. The trees, which are remarkably precise at detecting minimal changes in day length — mere minutes over a week — respond collectively to these cues, triggering coordinated seed production.
Dr Valentin Journé, the lead author of the paper explained that their inspiration came from a recent Science paper which demonstrated that temperature effects on leaf senescence shift at the summer solstice. Recognising that the solstice is the longest day of the year and occurs simultaneously across the Hemisphere, the researchers hypothesised that it could serve as a cue for synchronised reproductive activities.
Scientists involved in the study are also looking to see if there is a genetic component to this synchronised event, Quanta Magazine reported. They are looking at a gene called CONSTANS in particular which is found in all flowering plants. This gene responds to seasonal changes and circadian rhythm. In some plants, this gene in addition to others is responsible for flowering when the days are longer. However, this is still a hypothesis as the genes of the European beech tree need to be sequenced to find out more.
The regional synchronisation of seed production has significant ecological ramifications. Masting events provide pulses of resources for wildlife, while years of reproductive failure lead to famines for seed-eating animals. When these variations are synchronised on a sub-continental scale, they can cause wide-reaching disruptions in food webs. These include rodent outbreaks, migration patterns of ungulates and birds, and spikes in wildlife-borne diseases affecting humans.
