Relationship of Leaf Photosynthesis to Forage Yield of Tall Fescue¹

Abstract

Genetic variation exists for leaf photosynthesis in tall rescue (Festuca arundinacea, Schreb.), but little information exists on its relationship to forage yield. Therefore, net carbon exchange (NCE) of leaves of tall rescue genotypes was measured in the field during regrowth stages and compared to forage yield of the swards in the subsequeut harvest. Genetic variation existed for both yield and NCE on a leaf area basis, but no consistent relationship between these characters was found. Both NCE and forage yield were increased by irrigation during drought. Correlations between NCE and yield also tended to change from positive to negative with irrigation. Although NCE on a single leaf basis is a primary component of forage yield, other factors such as a environmental stress, canopy shape, and dry matter distribution will need to be considered if NCE is to be included in an effective selection index for improvement of forage yield.

Irradiance Response of Tall Fescue Genotypes with Contrasting Levels of Photosynthesis and Yield1

“…for both C 0 2 exchange rate (CER) of single leaves and yield (Nelson et al, 1975a). Similar findings have been reported for other cool-season perennial forage grasses (Wilson and Cooper, 1970;Carlson et al, 1971;Rhodes, 1972;Borrill et al, 1974).…”

“…Forage yield and CER (Nelson et al, 1974) were measured on three replications of 67 genotypes during 1972. Genotypes were grown as solid stands in 1.7 x 3.7 m field plots as described by Nelson et al (1975a). Cumulative yield of the first two cuttings and mean of two CER measurements during early and late June were used to select the genotypes used in the study.…”

“…Increased forage yield and decreased CER were associated with selection for small mesophyll cells when compared to selections made for large mesophyll cells in perennial ryegrass (Lolium perenne L.) (Wilson and Cooper, 1970). Nelson et al (1975a) reported an inconsistent relationship between CER and yield in clonal lines of tall fescue. Individual harvest period correlation coefficients between CER and yield ranged from -0.60 to +0.60 in three field studies, but the overall correlation coefficient was nonsignificant and negative.…”

“…' Canopy shading and development (Rhodes, 1973) and dry matter distribution (Treharne and Eagles, 1970) have been suggested as factors influencing the relationship between leaf photosynthesis and yield. Nelson et al (1975a) also suggested that genotype by irradiance interactions may influence the CER-yield relationship. In addition, genetic variation in diurnal trends in CER could affect this relationship (Pallas, 1973).…”

Photosynthesis in Tall Fescue

“…An allopolyploid series of tall fescue (Festuca arundinacea, Schreb.) was originally collected to study photosynthesis potential in wild tall fescue relatives varying in polyploidy (18, 22,26,28). We examined the light-driven reactions in the chloroplast thylakoids using this series (21,22).…”