High temperature patterns during seed maturation determine seed yield
and quality in oilseed rape (Brassica napus L.) in relation to sulfur
nutrition
Abstract
High temperatures (HTs) during the crop reproductive stage impact seed
yield and quality. The changing climate will require consideration of
the effects of repeated HT events following evidence for non-additive
effects due to beneficial stress memory or amplification of individual
event effects. Maturing seeds of the sulfur (S)-demanding crop, oilseed
rape, were exposed to several HT sequences that varied in intensity,
duration and frequency at the onset of seed maturation. The effects of
these sequences in combination with two contrasting S supplies are
reported. The results indicated that (i) as the number of HT days in a
sequence increased, fatty acid (FA) concentrations decreased, the
proportion of unsaturated FAs decreased, seed membranes were damaged,
desiccation tolerance was lost, and dormancy increased, regardless of
event intensity and (ii) a mild stress event prior to heat peaks had a
priming effect on desiccation tolerance and the phytohormones involved
in HT-induced thermoinhibition. Low S nutrition amplified or alleviated
the effects of the HT sequences due the requirement for S in enhancing
seed storage synthesis or inducing stress memory-associated mechanisms.
This work provides insights to define thermopriming protocols in
relation to the timing of quality building processes and their
respective optimal temperature.