Temperature sensitivities of Festuca arundinacea Schreb. and Dactylis glomerata L. ecotypes

summary The thermal responses of leaf growth and senescence were measured in four populations of Festuca arundinacea Schreb. and three of Dactylis glomerata L. with a range of geographical origins. Leaf extension was quantified by fitting logistic curves to lengths measured for up to 120 d in controlled environments at 20 °C or after transfer to 5 °C at emergence of the fourth leaf. Electronic position transducers were employed to observe rapid adjustments in leaf elongation rate in response to changes in the temperature experienced by the growing zone. Leaf segments were incubated in darkness on a thermal gradient bar giving a range of temperatures between 0 and 20 °C, and chlorophyll and protein were determined after 4 d of senescence. For each process, temperature sensitivities were determined as 0 10 , to give a profile of thermal response for each ecotype. Correlations between processes across ecotypes enabled possible relationships between temperature perception mechanisms to be identified. In their responses to chilling temperatures, mean extension rates measured over a period of one or more plastochrons were not closely related to short‐term rates. There was a significant negative correlation between chlorophyll stability in excised leaf tissue and mean long‐term extension rates. In general, ecotypes from the coldest habitats were the most sensitive to low temperature inhibition.