Carbohydrate Sampling in Kentucky Bluegrass Turf1

Abstract

AbstractThe percent total nonstructural carbohydrate (TNC) is often used as an indicator of the physiological status of cool season turfgrasses. However, the time of sampling during the day and the plant parts used for analyses may influence results. Growth habit differences of cultivars may also influence the TNC level of plant parts and the rate of accumulation at different times during the day. The purpose of this research conducted on Kentucky bluegrass (Poa pratensis L.) was to determine 1) TNC of five cultivars over three mowing managements, 2) whether TNC of leaf parts (blade or sheath) or the entire leaf (blade plus sheath) provided the best statistical separation of treatments, and 3) diurnal fluctuation of leaf blade TNC in cultivars of diverse leaf blade orientation.Five Kentucky bluegrass cultivars (‘Merion’, ‘Pennstar’, ‘Baron’, ‘Bonnieblue’, and ‘K‐150A’) maintained at three cuttings heights (1.3, 2.5, and 5.1 cm) in the field were utilized in these experiments. These cultivars were art of the 1972 Northeastern Regional Test established in 1972 on a Hagerstown soil (fine, mixed, mesic Typic Hapludalf). Upper canopy leaf blades (reel mower clippings), leaf sheaths, and entire leaves (blade and sheath) were analyzed for TNC. Blade tissues from intact tillers of Merion were analyzed for TNC and compared with upper canopy leaf blade TNC. Upper canopy leaf blades of Merion and two cultivars (‘Brunswick’ and ‘K‐183’) having diverse leaf blade orientation were sampled diurnally on 2‐hour intervals for TNCCuttings heights significantly affected TNC regardless of the tissue fraction analyzed. The 2.5‐cm height had significantly higher TNC than the 1.3 and 5.1 an heights. Entire leaf TNC provided a greater statistical cultivar separation than did sheath or blade tissue alone. K‐150A had significantly higher entire leaf TNC than Pennstar, Baron, and Bonnieblue, while Merion was also higher than Pennstar and Baron. Upper canopy leaf blade tissue of Merion had a much higher TNC level than leaf blade samples which included lower blades. The TNC of blade tissue was found to fluctuate significantly within 2 hours. Cultivars with different blade orientation exhibited similar diurnal TNC patterns. On the basis of these results, future TNC analyses should utilize the entire leaf (blade and sheath) for optimum statistical separations.