The effect of environmental conditions immediately before anthesis on potential grain weight was
investigated in wheat at the experimental field of the Faculty of Agronomy (University of Buenos
Aires, Argentina) during 1995 and 1996. Plants of two cultivars of wheat were grown in two
environments (two contrasting sowing dates) to provide different background temperature conditions.
In these environments, transparent boxes were installed covering the spikes in order to increase spike
temperature for a short period (c. 6 days) immediately before anthesis, i.e. between ear emergence and
anthesis. In both environments, transparent boxes increased mean temperatures by at least 3·8 °C.
These increases were almost entirely due to the changes in maximum temperatures because minimum
temperatures were little affected. Final grain weight was significantly reduced by higher temperature
during the ear emergence–anthesis period. It is possible that this reduction could be mediated by the
effect of the heat treatment on carpel weight at anthesis because a curvilinear association between
final grain weight and carpel weight at anthesis was found. This curvilinear association may also
indicate a threshold carpel weight for maximizing grain weight.