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Influence of Temperature on Leaf Dark Respiration of Diverse Tall Fescue Genotypes¹

Reduction of dark respiration (R_D) of mature tissues could improve herbage yield of tall fescue (Festuca arundinacea Schreb.), especially during summer. Our objectives were to 1) examine the response of R_D of collared leaf blades to temperature in seven genotypes of tall fescue, and 2) examine the interrelationships between R_D, concentrations of water-soluble carbohydrate (WSC) and N Of leaf blades, and sward yield components. Seven randomly selected genotypes were vegetatively propagated into pots. In Exp. I, established plants were allowed to regrow in controlled- environment chambers at leaf blade temperatures of 20, 27, or 34°C, while in Exp. II regrowth of genotypes was at 20, 25, and 30°C. A 14-h photoperiod with photosynthetic photon flux density of 650 and 665 µmol m^–2 s^–1 was provided in Exp. I and II, respectively. After 6 weeks of regrowth at the specified temperatures, R_D of center-sections of recently-collared leaf blades was measured manometrically and CO₂ exchange rate (CER) was measured on similar leaves using an infrared gas analyzer. Within both experiments, R_D at temperatures of 27°C or less were similar, averaging 10.8 and 6.8 µmol 0₂ kg^–1 s^–1 for the genotypes with the highest and lowest R_D, respectively. At 30°C genotypes did not differ in R_D but rates averaged 40% higher than those at 27°C or less. No plants survived at 34°C. The CER decreased as temperatures increased and was not related to R_D or any other characteristic measured. At 27° C or less concentrations of WSC were lowest, while concentrations of N were highest in leaf blades of genotypes with high R_D. As temperatures increased, concentrations of WSC decreased while N increased. Genotypes with high R_D had significantly lower yield per tiller (YPT) and mass of WSC per stem base when compared with low-R_D plants. Genotypic variation for R_D was apparent at temperatures between 20 and 27°C. Therefore, selection for altered R_D would be more efficient at temperatures favorable for growth. Low N and high WSC concentrations of leaf blades may result from selection for low R_D of collared leaf blades. Large stem bases with high concentration of WSC may also be selected indirectly with low R_D, resulting in high YPT.

Key Words: Festuca arundinacea Schreb. • Yield per tiller • Tillering • Water-soluble carbohydrates • leaf blade N • Genetic variation • Leaf area expansion • Specific leaf weight • CO₂ exchange rate

² Former graduate research assistant (now assistant professor, Dep. of Agron., Purdue Univ., Lafayette, IN 47907), professor and associate professor, respectively, Dep. of Agron., Univ. of Misouri, Columbia, MO 65211.

Received for publication May 27, 1983.