Comparison of the abilities of vegetation indices and photosynthetic parameters to detect heat stress in wheat

•PRI, CIred-edge, and NDRE can detect heat stress, which is related to Fv/Fm, LCC, and Pn, respectively.•Fv/Fm is the most sensitive physiological parameter to indicate the start and end of slight heat stress.•PRI is the most sensitive VI, while it only works well at the heavy level or the late stage.•Fv/Fm is more sensitive than PRI to the heat stress especially at the slight level or early stage.