Yield components were only impacted in reproductive plant
parts developed after the stress
Yield components were not drastically impacted by the high temperature
sequences applied at GS72. Under HS, no effect of temperature was
observed on yield of podsL≥5cm, meaning that the seeds
from podsL≥5cm experienced a normal filling period.
Therefore the impact of the heat sequences on total seed yield was the
consequence of a yield reduction in seeds from
podsL<5cm, which resulted from reductions in
seed number and individual seed weight, even though neither component
was significant. Indeed, abortions of young pods during the T-modality
exposure and/or failure of pollination in the flowers present during
this period might have occurred (Young et al. 2004). Changes in
the reproductive strategy might also have reduced the incidence of late
flowering (specific to indeterminate species) to the benefit of filling
seeds in already developed pods. These observations are consistent with
prior studies in pea (another indeterminate growth species) that
demonstrated heat-stress modification of seed distribution along the
main stem, which led to larger quantities of seeds on the basal parts
than on the upper parts where reproductive organs are younger. These
results explained the maintenance of seed yield from basal reproductive
parts due to a higher allocation rate of carbohydrates and excluded the
direct effects of heat stress on developing seeds (Guilioni, Wéry &
Lecoeur 2003). The non-significant effect of S on seed yield components,
other than the total seed number, indicates that the LS supply in our
study satisfied growth rate and yield requirements. Nevertheless, LS
conditions impacted a few quality criteria related to nutritional value
such as seed S content, SFAs and UFAs (Figure 2), as well as the
concentrations of phytohormones involved in stress-induced secondary
seed dormancy.