Article révisé par les pairs
Résumé : Chilling temperatures drastically inhibited the photochemical quenching of chlorophyll fluorescence (qQ) measured in intact leaves photosynthesizing under steady‐state conditions. This effect appeared, however, to be characteristic of chilling‐susceptible plant species and was not observed in plants which are known to be chilling‐tolerant, indicating that the measurement of qQ can serve in practice to estimate rapidly the relative chilling tolerance of crop plants. A large number (28) of sweet sorghum (Sorghum bicolor) and Sudan grass (Sorghum sudanense) genotypes were screened for chilling tolerance using this rapid qQ method. Although sweet sorghum and sudan grass obviously behaved as chilling‐sensitive plants, a considerable variation for chilling susceptibility was observed among the different genotypes tested. Some sweet sorghum varieties, such as ‘Dale’ and ‘Keller’, and most of the sudan grass varieties appeared to possess a certain degree of resistance towards low temperature stress, indicating the existence of useful germplasms in Sorghum for improving stress tolerance. Copyright © 1989, Wiley Blackwell. All rights reserved