Carbohydrate loading is a strategy often utilized by endurance athletes. The extra carbohydrates are stored in muscle tissue as glycogen, which is quickly converted to energy during the sporting event. I engage in a different type of carbohydrate loading during Sunday dinners at Momma Fidanza’s house: homemade spaghetti alla chitarra. This is a long, square-cut pasta traditionally made in Abruzzo, Italy, the region where Momma is from. After that meal, I don’t feel energized; I just want to take a nap.
In turfgrasses, the major total nonstructural carbohydrates are glucose and fructose (monosaccharides) and sucrose (disaccharide), along with some starches and fructans (oligosaccharides). These carbohydrates are the byproducts of photosynthesis and are typically stored in roots, crowns and rhizomes or stolons, depending on the turfgrass species.
Intensively managed turfgrasses are continuously exposed to a wide range of stresses, such as mowing, traffic, low or high temperatures, salinity, drought, diseases, insect pests and much more. Turfgrass with depleted carbohydrate reserves is more vulnerable to those stresses. In botanical research, carbohydrate content is often measured to indicate plant growth and physiological responses to environmental conditions and various cultural practices. Thus, carbohydrate concentration is often used to determine the health and physiological status of turfgrasses.
Research was conducted at the University of Illinois (Urbana) to investigate the effects of mowing height on carbohydrate levels in creeping bentgrass (Agrostis stolonifera). Conventional laboratory methods for analyzing carbohydrate content in plant tissues is a tedious and time-consuming process. However, this study utilized near infrared reflectance spectroscopy. From a turfgrass science perspective, the researchers conducted a preliminary test that compared conventional laboratory analysis of carbohydrates versus spectroscopy. They confirmed that near infrared reflectance spectroscopy was a valid instrument to measure carbohydrate levels in turf clippings.
Eight creeping bentgrass cultivars (Crenshaw, L-93, Penncross, Penneagle, Penn G-6, Putter, Seaside II and Southshore) were mowed at a bench-height setting of 0.25, 0.5 and 0.75 inches (6.4, 12.7 and 19 millimeters). The replicated and randomized plots were mowed three times per week and received routine maintenance of fertilizer, weed, disease and insect control, and irrigation as needed. Turfgrass clippings from each plot were collected periodically during May through December over four consecutive years of this field study. With each collection time, clippings were immediately freeze-dried in liquid nitrogen, then subjected to various preparations for the carbohydrate analysis by the spectroscopy method.
Over the four-year study period, no carbohydrate differences were detected among the eight creeping bentgrass cultivars. On 13 of 29 sampling dates over the four-year study period, creeping bentgrass mowed at 0.25 inch accumulated more carbohydrates compared to the 0.5-or 0.75-inch mowing heights. Why? The researchers commented that carbohydrates are mobilized from the leaf blades to the sheath, crown, and stolon or rhizome tissues at night, and then during the next day the leaf carbohydrate levels return to their normal concentration. Since the clippings were collected in the early morning, those clippings from the lowest mowing height probably contained more sheath and stem tissues, which contained more carbohydrates.
However, combining information from all the cultivars, there were seasonal differences with carbohydrate levels. For example, carbohydrate contents started to decline by mid-July and were at their lowest in August. By September, there was an increasing trend of carbohydrate accumulation, and the highest concentration of carbohydrates was measured in October and November. Those carbohydrates are like antifreeze to help the plants survive the winter and then are utilized to grow roots by the spring.
The researchers also stated: “Since it is easier to maintain plant health rather than resurrect it, early detection of plant stress is critical for efficient turfgrass management.” Thus, turfgrass management practices will be most efficient, beneficial and impactful with turf that is healthy, resilient and actively growing.
Source: Narra, S., T.W. Fermanian, J.W. Swiader, T.B. Voigt and B.B. Branham. 2004. Total nonstructural carbohydrate assessment in creeping bentgrass at different mowing heights. Crop Science 44:908-913.
Mike Fidanza, Ph.D., is a professor of plant and soil science in the Division of Science, Berks Campus, at Pennsylvania State University in Reading, Pa. He is a 24-year member of GCSAA.