Evidence for non-additive effects of successive heat
stress events as a consequence of stress response amplification or the
priming effect
Most measured variables illustrated the non-additive effects of the
successive events, meaning that the cumulative impact of the respective
effects of each SES (e.g. mod2, mod3, SEScml) differed from the effect
of CES (mod1). When a mismatch was observed, the effect of the CES was
either (i) higher than the effects of the SEScml or (ii) lower than the
effects of the SEScml. Under HS, the CES effects (absolute value) on
total yield, seed conductivity, the ABA:GA3 ratio and seed N
concentration were higher than the SEScml effects, whereas the CES
effects were lower for the [raffinose+stachyose]:sucrose ratio and
the FA concentration (Table 4), but to a lesser extent for the FAs.
Similar mismatches were observed under LS for seed conductivity, the
ABA:GA3 ratio (higher CES effects than SEScml effects), FA concentration
(lower CES effects than SEScml effects) but not for total yield, the
[raffinose+stachyose]:sucrose ratio, for which the CES effects were
lower than (or equal to) the SEScml effects. Therefore, this analysis
highlights that S availability determines the magnitude (value and
direction of variation) of the mismatches between the SEScml and CES
effects.