Effect of temperature and carpel size during pre-anthesis on potential grain weight in wheat

The effect of environmental conditions immediately before anthesis on poten tial grain weight was investigated in wheat at the experimental held of the Faculty of Agronomy (University of Buenos Aires, Argentina) during 1995 an d 1996. Plants of two cultivars of wheat were grown in two environments (tw o contrasting sowing dates) to provide different background temperature con ditions. In these environments, transparent boxes were installed covering t he spikes in order to increase spike temperature for a short period (c. 6 d ays) immediately before anthesis, i.e. between ear emergence and anthesis. In both environments, transparent boxes increased mean temperatures by at l east 3.8 degrees 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 anthes is because a curvilinear association between final grain weight and carpel weight at anthesis was found. This curvilinear association may also indicat e a threshold carpel weight for maximizing grain weight.