High temperature tolerance can be characterised by
measuring various plant productivity traits in different
developmental stages. The present work investigated the
effect of exposure to high temperature (30-35°C) at first
node appearance, during early embryo development and
in the grain-filling stage on the yield parameters of two
winter wheat varieties. Periods of high temperature had
diverse effects on wheat plants in different phenophases.
The greatest differences between the various developmental
stages were found for grain number, grain yield
and thousand-kernel weight. Heat stress was demonstrated
to have the least effect on total grain number and
number of grains per spikelet on the main spike during
the grain-filling period. The most pronounced reductions
in the traits examined were detected when heat stress
was applied during the early embryo development stage
