Gas Exchange and Leaf Area Characteristics of Four Tall Fescue Selections Differing in Forage Yield1

Abstract

Gas exchange and leaf area characteristics of four tall fescue (Festuca arundinacea Schreb.) selections differing in forage yield were examined under greenhouse and laboratory conditions to determine if these characteristics might be related to yield differences. Carbon dioxide exchange rates (CER) and specific leaf weight of leaf blades of ten genotypes per selection were measured in December 1978 and April 1979. In April 1979, dark respiration and transpiration rates of leaf blades were also evaluated. Leaf elongation rate, leaf width, and leaf area expansion rate were assessed during three measurement periods.In December 1978, the lowest‐yielding selection, TFM 16, had 20% greater CER than the high‐yield selections, TFM 26 and TFK 4, and 8% greater CER than TFK 12. Differences in CER were not statistically significant in April. No significant differences among selections for transpiration, dark respiration, or specific leaf weight were found.High yielding TFM 26 had significantly greater leaf elongation and leaf area expansion rates in one measurement period (by 28 to 48% and 24 to 43%, respectively), but differences among selections were not significant in two other periods. Low‐yielding TFM 16 had leaves that were more than 20% narrower than those of the other selections. Leaf width was a relatively more stable morphological character than leaf elongation or leaf area expansion rate.