What Makes a Plant TIC TOC?
Most of us are all too familiar with our own body clocks, jet lag anyone? This subconscious rhythm of a 24-hour cycle that flows through our bodies keeps us in tune with the solar day. The body clock affects the daily rhythm of many physiological processes; there are optimal times for eating, sleeping, coordination, muscle strength and alertness to name but a few. What most of us perhaps are not so familiar with is that we are not the only organisms which possess such a power, in fact plants, algae, animals and cyanobacteria all show signs of circadian rhythms.
Today we will be discussing what makes a plant TIC TOC.
Yes that’s right, plants can tell the time.
As early as 1729, recorded evidence of circadian rhythms began to shed light on the phenomenon. The French scientist Jean-Jacques d’Ortous de Mairan noted that mimosa plants exhibited 24-hour patterns in leaf movement, despite being kept in constant darkness. The leaves appear to droop during night time hours and perk up in the daytime.
Similarly the Daisy (Day’s eye) flower knows when to open in the morning (when sun is more likely) and close at night. It’s very name being influenced by its circadian rhythm tendencies. This body clock is crucial for survival, allowing plants to sync up to the light cycles of the surrounding environment and tell the plant when the best time is for processes such as photosynthesis (eating), hibernation (sleeping) and germination (growth), not all too dissimilar from us humans really.
So how does a plant tell the time?
A plant’s body clock, like ours is heavily regulated by light exposure and day length. In plants the photoreceptors (specialised cells that can sense light), receive a dose of light (red and blue) and in turn cause the plant to maintain a steady rhythm that is made up of two interacting feedback loops; a morning loop and an evening loop. The loops are controlled by the specific expression of certain genes e.g. TOC1, CCA1 and TIC (gene not yet identified), the switching on and off of genes regulates the feedback loops and keeps them on a tight schedule. These loops combined run continuously on a 24-hour cycle, however they are not perfect and any deviations from the 24-hour timeframe can be adjusted for or ‘reset’ via a good dose of natural light. Like changing a battery in a watch, sometimes plants require a little help.
Understanding plant body clocks will help us to improve crop production procedures and learn the best time to plant and harvest crops so to maximise yield. Through such research, we are already capable of inducing or prolonging germination and maturation processes in order to have plants ‘ready’ for us on our schedule, how about those carnations in time for Mother’s Day? However, there is still scope for further developments. Continued research will further enhance improvements within this field and help us to fully understand what it is that makes a plant tick.
Extra reading
https://en.wikipedia.org/wiki/Circadian_rhythm
McClung CR. Plant Circadian Rhythms. The Plant Cell. 2006;18(4):792-803. doi:10.1105/tpc.106.040980.
Sanchez, S. E., & Kay, S. A. (2016). The plant circadian clock: from a simple timekeeper to a complex developmental manager. Cold Spring Harbor perspectives in biology, a027748.
