Abstract
The objective of this study is to determine the potential of photosynthesis for the detection of heat stress in three wheat genotypes ‘Grekum 476’, ‘Otan’ and ‘Alba’, which are known to differ in their leaf rolling ability. The results of measurements of gas-exchange, stomatal conductance and pigment determination indicate that the use of a temperature of 40 °C allows to distinguish the non-rolling and leaf rolling wheat genotypes in their photosynthetic responses to heat stress.High temperature acclimation by the leaf rolling wheat genotypes caused marked changes in the pigment composition and function of the photosynthetic apparatus. Thus, stomatal regulation (changes in gH 2 O values), the changes in WUE and modification of the photosynthetic pigment apparatus as well as the up-rolling of the flag leaf at a higher irradiance are essential factors that contribute to avoid heat and drought conditions as well as photoinhibition of the photosynthetic apparatus in major parts of the leaf. The two most leaf up-rolling wheat genotypes ‘Grekum 476’ and ‘Otan’ also exhibited the best stomata regulation, a higher WUE and the highest P N -rates at a 40 °C heat stress than the non-rolling ‘Omskaya 9’ or the low leaf rolling ‘Alba’ genotypes. Thus, photosynthetic net CO 2 assimilation P N and the high degree of flag leaf up-rolling under heat conditions parallel the higher field productivity of ‘Grekum 476’ and ‘Otan’.