Plant Growth Conditions
For the phenotyping, 190 Arabidopsis thaliana accessions were
grown on soil containing limiting, intermediate and optimal amounts of
nitrogen and as described in Pandey et al. 2019. The accessions that
were obtained from the Nottingham Arabidopsis stock centre (NASC) and
are listed in Table S1. The plants were grown on pots (⌀ = 6 cm, h = 5.5
cm) containing the same mass of adjusted white peat soil (Gramoflor
GmbH). The seeds were germinated for one day under short day (8h/16h)
condition at 20°C/16°C and 150 µE m-2s-1 of light intensity. To ensure flowering, all
accessions were vernalized for eight weeks at 4°C under long days and
light intensity of 7 µE m-2 s-1.
After this, plants were transferred to new pots. Four plants in two pots
(n=4) were grown under long days at 21°C/17°C (day/night) and 150 µE
m-2 s-1 of light intensity. Early
rosette (ERD) diameter was the rosette diameter ten days after pricking
and the final rosette diameter (FRD) at the time of flowering. Rosette
diameters were measured from pictures taken at these stages using ImageJ
(Schneider, Rasband, & Eliceiri, 2012). Flowering time (FT) was scored
at the number of days from pricking of the plants to the day of first
open flower. Seed yield (YIE) was quantified from two plants together by
dividing the total weight of the seeds with the weight of hundred seeds
and multiplying by 100. In all experiments, to minimize stochastic
variation the replicates were distributed across different trays and the
trays were periodically rotated in the growth chamber.
For the adaptability experiments, 19 accessions were selected based on
their ERD and FT plasticity to N (Table S8) and were germinated and
vernalized as described above. For the experiments under short days,
long days (control condition), and low light, five pots with two plants
each were prepared for every accession and condition (n = 10). For the
experiments under high light, five plants were transferred to big pots
(⌀ = 13 cm, h = 10 cm) and in the polytunnel (natural light and
temperature), three plants were transferred to big pots (⌀ = 13 cm, h =
10 cm) in both conditions resulting in n=15. For the experiments under
short day (8h/16h) and the long day control (16h/8h), the temperature
was 20°C/16°C (day/night) and light intensity 120 µE
m-2 s-1. In the low and high light
the plants were grown at long-day 16h/8h with temperature 21°C/17°C
day/night cycle with light intensity of 20 µE m-2s-1 (low light) and 750 µE m-2s-1 (high light). The experiment in the polytunnel
under natural conditions was performed during summer 2020.