How do plants know when to produce flowers?
Research sheds new light on how cold temperatures over winter primes some plants to flower in spring.
Plants are not able to move around and so they need to be able to adapt their growth and development to seasonal changes in their environment. For example, prolonged exposure to cold temperatures during winter can prime some plants to flower when temperatures increase in the spring — a process called vernalization. In these plants, extended periods of cold temperatures lead to lower activity of a gene called FLC, which normally inhibits flowering.
In the plant Arabidopsis thaliana, vernalization requires several months of exposure to temperatures between 0–6°C. Recently, A. thaliana plants from southern Europe were found to vary in the temperature requirements for vernalization, responding to temperatures higher than 6°C. This suggested that plants from northern Europe might vernalize preferentially at lower temperatures. Here, Susan Duncan and colleagues compared vernalization in a collection of A. thaliana plants (or ‘accessions’) sampled from different regions of Sweden and the UK.
The experiments show that all the accessions needed temperatures above 0°C to vernalize and that vernalization still worked relatively well at temperatures as high as 14°C. The optimal temperature range for vernalization differed between the accessions, but plants from more northern areas did not necessarily vernalize at lower temperatures. For example, for one particular accession from northern Sweden, the temperature that is optimum for vernalization was 8°C, a notably higher temperature than expected.
Historical local climate records suggested that this accession would vernalize before the first snowfall of the winter in North Sweden. Duncan and colleagues confirmed this proposal with field experiments. Plants were grown in natural field sites in September and then moved into a greenhouse. The experiments show that the plants complete vernalization by November, which strongly suggests that FLC is silenced during autumn rather than during winter, as previously thought. This changed temperature response is due, in part, to a small number of tiny genetic differences in regions of the FLC gene that do not code for protein.
These findings have important implications for future studies of vernalization and flowering time, and for understanding how plants will adapt to on going and future climate change. The next step is to understand what causes these changed temperature responses at a molecular level, which should enable selective breeding for flowering and harvest date in a range of crops.
To find out more
Read the eLife research paper on which this eLife digest is based: “Seasonal shift in timing of vernalization as an adaptation to extreme winter” (July 23, 2015).
