Turf Quality of Kentucky Bluegrass Cultivars and Energy Relations 1

Future turfgrass improvement will depend upon recognizing those physiological properties responsible for stress tolerance and recovery from injury. Once recognized, these properties may be incorporated into the screening program of cultivar improvement efforts. Because energy capture and transport are basic to plant growth, we measured the variation in these processes between several Kentucky bluegrass ( Poa pratensis L.) cultivars of varied origin and growth habit. In turn, CO 2 ‐exchange rate (CER), clipping growth rate, and nutrient factors were evaluated for their correlation with turf quality. Field plots were on an Enfield silt loam (coarse‐silty over sandy skeletal, mixed, mesic, Typic Distrochrept). Carbon dioxide exchange rate was measured on plots of 15 cultivars during mid‐summer, 1978, and nine cultivars during late summer, 1980. On both dates, CER differed between cultivars and in 1978 were positively correlated with turf quality. Correlations between CER and clipping growth were significant but apparent photosynthesis was not related to leaf P and K content or nutrient efficiency ratios (mg dry wt. mg −1 K or P). No significant differences in photosynthate partitioning to roots were noted between 10 cultivars in August or October 1978. This was based upon 14 C recovered from roots 2 days following exposure of turf to 14 CO 2 for 15 min. Nevertheless, the percentage of current photosynthate translocated to roots was positively correlated with the size of the root system and negatively correlated with clipping production. Kentucky bluegrass cultivars which partition more energy to roots appear more likely to produce quality turf. Of the cultivars tested, ‘Enmundi’ possessed the most favorable energy distribution pattern and produced a quality turf.