The thermal response of leaf extension rate in genotypes of the C-4-grass Miscanthus: an important factor in determining the potential productivity of different genotypes

Thermal responses of plant extension rate are reported for 32 genotypes of the C-4 grass Miscanthus, Displacement transducers were used to measure plant extension rate as temperatures were stepped between 20 degrees C and 5 degrees C. Leaf extension accounted for 83% of the plant extension. The Q(10) between 10 degrees C and 20 degrees C for the genotypes varied from 3.0 to 4.7. The relationship between temperature (5-20 degrees C) and plant extension rate was found to be described adequately by fitting a third order polynomial, An estimate of the effect of differences in the thermal response of plant extension rate on the potential yield of the genotypes was calculated for Irish climatic conditions using a simple growth model, Potential yield varied between 3 and 23 t ha(-1) year(-1). This demonstrates the critical role which differences in leaf expansion rate can play in the selection of more productive genotypes. The significance of vapour pressure deficit on the estimates of thermal response of plant extension rate are discussed.