Temperature dependence of wheat development

Among the abiotic stress factors influencing the growth and productivity of wheat varieties, extremely high temperatures have the most limiting effect. In an experiment set up in the gradient chamber of the Martonvásár phytotron to test the effect of various temperatures on four winter wheat varieties and one variety of spelt, substantial differences were observed in the heat stress tolerance of the varieties. There was a considerable reduction in the number of shoots and spikes as the result of heat stress, leading to a drastic loss of grain yield. It was clear from changes in the biomass and in the grain:straw ratio that extremely high temperatures led to a substantial reduction in the ratio of grain to straw in the varieties tested. In response to high temperature the wheat plants turned yellow earlier due to the rapid decomposition of the chlorophyll content. This resulted in a considerable shortening of the vegetation period and early ripening. Reductions in the parameters tested were observed at different temperature levels for each variety, indicating considerable differences in the ability of the varieties to adapt to abiotic stress factors.