Flowering time and seed dormancy control use external coincidence to generate life history strategy

摘要

Plants adjust when they grow, develop flowers and produce, or ‘set’, seeds in response to changes in temperature and day length. It is therefore unsurprising that climate change alters the timing of these important events in plants' lives; for example, many plants are adapting to rising temperatures by flowering earlier and growing for longer. The environmental signals that control when a plant flowers, and the genes that underlie this process, have been well studied in the model plant Arabidopsis thaliana. This plant's ability to quickly colonize and thrive in disturbed habitats—including agricultural land, construction sites, and waste ground—is partly because some of its seeds lie dormant in the soil, for up to several years, before they start to grow. Whether or not a seed undergoes a period of dormancy is controlled by the temperature that the seeds experienced when they were developing; this in turn is influenced by earlier events, such as when the flowers first developed, and when the plant first started to grow from its seed (a process called germination). To try to understand these complex interactions, Springthorpe and Penfield developed a computational model of the major events in the life of an Arabidopsis plant. Data collected from Arabidopsis plants that normally germinate in winter and spring were then used to check whether the model could accurately represent what happens in nature. The analysis confirmed that the timing of seed setting depends mostly on the environmental temperature. Springthorpe and Penfield then showed that plants both flowered and set seed earlier in response to increases in temperature, so that the seeds were shed precisely when the temperature was between 14°C and 15°C. Springthorpe and Penfield discovered that rise in the average temperature when a plant set seed from 14°C to 15°C had a dramatic effect on the seeds. Almost all of the seeds that developed below 14°C became dormant, while very few of the seeds that developed above 15°C became dormant. From their findings, Springthorpe and Penfield predict that the temperature control of flowering time has evolved to constrain when seeds are set and ensure that plants produce a mixture of seeds some that will become dormant, and some that will not. Their findings also show that modelling the whole life history of an organism has the potential to reveal strategies that are not obvious when studying single events in isolation. If the model was extended to include genetic variation across populations of plants, this approach could give new insights into how individual genes help plants adapt to weather and climate.