Plant & zo
The science of plants and more
How to predict winter
It’s a challenge, year after year, to stop growing on time. And, after winter, to start again. Annual plants have it easy. They germinate, grow, flower, set seeds, disperse them, and die. Simple. Easy, first one thing than the next. Being a perennial is not that easy. Every year you need to stop growing before winter arrives. Then start up again, and flower as well. How do they recognise the right moment for this all?
For annuals we now more or less know how they do it. But for perennials it is another story. They do things differently than annual plants, do more things, sometimes even multiple things at once. Take for example growing and flowering. For annuals this is regulated by the gene FT. When the FT gene is turned on, the plant grows, it develops new leaves and stems. Is the FT gene turned off? Then the plant starts flowering. Easy.
Not in perennials. Perennials, it turned out have multiple FT genes. To understand what these FT genes do, researchers from Sweden studied the FT genes from European aspen, a tree from the poplar family. The FT genes in European aspen come in two types, FT1 and FT2. The researchers followed the genes a whole year and had a look at what happens when these genes are turned off completely.
Growth, but not flowering, is regulated by these two genes
In growing leaves FT2 is turned on. But, during shorter days the researchers noticed that there is less FT2. By the time, in autumn, the tree forms buds, FT2 is turned off. When FT2 is completely switched off, the European aspen start making buds even when the days are still very long. It turns out that FT2, just like FT from annuals, is needed for growth and prevention of starting the next step, bud formation, to early.
The researchers noticed FT1 was only turned on during the winter, in the buds. The colder, the more FT1. When, in spring, the first leaves appeared, FT1 was already turned off. Switching the FT1 gene completely off, and the researchers noted that the first leaves did not appear in spring. The buds remained close. This suggest that FT1 wakes the buds up from hibernation. How exactly? That is still a mystery.
In perennials, the daylength coupled FT2 gene is regulating growth, just like FT in annuals. In contrast in perennials FT1 is coupled to temperature, not daylength. Allowing FT1 to regulate the hibernation of buds. Growth, but not flowering, is regulated by these two genes. FT1 and FT2 help perennials, to stop on time with growing, and, when winter is over, to start growing again.
Domenique André, Alice Marcon, Keh Chien Lee, Daniela Goretti, Bo Zhang, Nicolas Delhomme, Markus Schmid, Ove Nilsson (2022) FLOWERING LOCUS T paralogs control the annual growth cycle in Populus trees. Current Biology, https://doi.org/10.1016/j.cub.2022.05.023