Figure 6. Chlorophyll (Chl) content in leaf (A) 1, (B) 3, (C) 5
and (D) 10 or more for control (18°C night and day) (red) and cold
treatments (5°C night and 18°C day) (blue) in a growth chamber.
Asterisks indicate the significance of the Student’s t-test between the
cold and control treatments: ***: p < 0.001, **: p <
0.01, *: p < 0.05, NS: non-significant. Corresponding
experimentations was 20HP01.
Along with measuring growth, chlorophyll was measured in leaves 1, 3,
and 5 and the leaf ranked at 2/3 of the total number of leaves (i.e.,
leaf 10 or more). Chlorophyll content was higher in stressed plants than
in control plants after being transferred outside. Chlorophyll content
was higher on day 1 in leaf 1 in the control treatment than in the cold
treatment, which reflected the influence of the recent cold treatment in
the growth chamber (Fig. 6A). Seven days after transfer outside, the
chlorophyll content became higher in the cold treatment than in the
control treatment. This result was observed for all measurements for
leaves 3, 5 and 10 or more, with a high level of significance for leaves
3 and 5 (Fig. 6B and C).
Impacts of early sowing on yield and yield-related
traits
We studied impacts of ES date on late development and yield in the 2022
experiments (22TE01-02). We measured morphology, yield, number of seeds,
thousand kernel weight, seed weight, oil content and seed lipid
composition (Table 2). ES did not influence plant height but did result
in later flowering (111 days) than that of normal sowing (79-86 days)
(i.e., 9-16 d later). Flowering occurred earlier with ES (20 June 2022)
and was more synchronized for its three replicates than those of normal
sowing, which flowered from 29 June-6 July 2022. ES increased the seed
yield and the oil yield (770 kg/ha) compared to that of normal sowing
(430 kg/ha) (i.e., +80%) due to a slightly higher oil content. ES
decreased the oleic acid content in seeds significantly and increased
the contents of linoleic and palmitic acids.
Impacts of night chilling at early stages on final
yield-related
traits
To study impacts of early chilling stress on final traits, plants were
stressed in the cold and control treatments described previously. After
three weeks in growth chambers, the cold treatment was stopped, and
plants were transferred outside to the high-throughput phenotyping
platform Heliaphen.