A Carbon‐14 Technique for Measuring Photosynthate Distribution in Field Grown Turf 1

The effect of management or environmental factors on the short‐term distribution of current photosynthate within field grown turf has received little study. However, variation in the initial energy flow within turfgrasses certainly influences the longer term energy levels and ultimate survival of turf. A technique is described by which photoassimilated carbon was followed within ‘Merion’ Kentucky bluegrass ( Poa pratensis L.) grown as a closely mowed turf under field conditions. A 189 cm 2 area of grass was covered with a glass bell jar into which introduced 15 μCi of 14 CO 2 . Depending on climatic conditions, between 19 and 69% of the 14 C applied was recovered from a 10.5‐cm plug of turf harvested within 2 hours of treatment. During the 15 min exposure period, the temperature within the bell jar increased, however, 14 CO 2 sufficient for tracer analysis was assimilated presumably via a normal carbon reduction pathway. The utility of this technique is illustrated in a fertility experiment which showed that high fertility turf (24‐4‐8 or 48‐8‐16 g/m 2 N‐P‐K) often fixed more 14 CO 2 than did low fertility grass (12‐2‐4 g/m 2 ). Photoassimilated 14 C translocated to roots at a greater velocity in September than in December but the quantity translocated was greater in December. During late summer, photosynthate moved more rapidly to roots of low fertility turf and accumulated in deep roots more than it did in heavily fertilized turf. This technique appears to provide an effective method for measuring the short term energy distribution within turfgrass sod grown under natural conditions.