Global warming and earlier flowering: a thermogradient tunnel experiment
The life histories of plants are synchronised to seasonal changes in environmental conditions such as the temperature and light availability. In 2012, researchers found that the flowering time has advanced by 1 day per decade in 490 flowering species responding to warming spring temperatures over 20-50 years. Understanding how ecosystems will be impacted by climate change, it is important to investigate plant growth, seed production and seedling emergence over multiple generations.
Dr Steven Footitt and colleagues from the University of Warwick and Boğaziçi University tested the potential for changes in plant growth and seed germination of the model plant species Arabidopsis thaliana in a thermal gradient of +4°C. The wide distribution of Arabidopsis ecotypes (populations that are adapted to local environmental conditions) make it an ideal indicator species for investigating the impact of global warming on plant phenology. The researchers found that an obligate winter annual responds more positively to global warming than an obligate summer annual ecotype. Earlier this summer, the researchers determined genome‐wide expression patterns over an annual dormancy cycle in two Arabidopsis thaliana ecotypes.
Researchers used two Arabidopsis thaliana ecotypes adapted to the warm/dry Cape Verdi Islands (Macaronesia; Cvi), and the cool/wet climate of the Burren (Ireland; Bur). The scientists created a thermogradient tunnel with a thermal gradient of +4°C to produce a realistic global warming scenario for the experimental area between 2011-13 and 2080. Trays of 24 plants were placed at the cool/ambient (C) end and the warm (W) end of the tunnel. Flowering time, plant biomass, height and seed yield were measured. Researchers collected the mature seeds of the first population (F1), and then used the F1 seeds to grow plants again in the tunnel. Seeds were collected again from the second population (F2) and seed germination and seedling emergence was tested.
The simulated global warming reduced summer annual plant size and seed yield in a summer life cycle. In a winter life cycle, increasing temperatures advanced flowering time by 10.1 days °C-1 in the winter annual and 4.9 days °C-1 in the summer annual. The seedling emergence timing of the F2 generation responded to the environment experienced during the F1 seed production. The Irish ecotype showed more phenotypic plasticity in rosette leaves than the Macaronesian ecotype. Total emergence of the Irish ecotype decreased at higher emergence whilst the Macaronesian ecotype’s emergence increased.
“We reveal a strong adaptive response to global warming in the winter annual ecotype Cvi,compared to a weaker response in the summer annual ecotype Bur,” Footitt and colleagues said.
“Seedling emergence timing observed in the north European summer annual ecotype may exacerbate the negative impact of predicted increased spring and summer temperatures on their establishment and reproductive performance.”
“In contrast, seedling establishment of the Macaronesian winter annual may benefit from higher soil temperatures that will delay emergence until autumn, but which also facilitates earlier spring flowering and consequent avoidance of high summer temperatures.”
You can watch a short video of Dr Steven Footitt explaining the thermal gradient tunnels at Warwick Crop Centre.