Carbohydrate Quantification and Relationships with N Nutrition in Cool-Season Turfgrasses

AbastractEnvironmental and cultural variables are known to influence the carbohydrate status of cool-season turfgrasses. This greenhouse study was conducted to 1) develop a technique utilizing standard analytical procedures which would simplify carbohydrate analysis of plant tissue while increasing specificity and sensitivity, and 2) to use these methods to determine if any one carbohydrate fraction in leaf, stem, or root tissue of three turfgrass species is more sensitive than another to applied N treatments. A single aqueous extraction was required for quantification of glucose, fructose, sucrose, and fructans using glucose oxidase and invertase coupled with two standard colorimetric tests. Data analysis showed that the portion of the error term which could be directly attributed to the analytical technique across the three turf species was 1.19%. The procedure was precise, simple, and highly efficient. ‘Baron’ Kentucky bluegrass (Poa pratensis L.), ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.), and annual bluegrass (Poa annua L.) were grown in a greenhouse at 5 and 10 mM NO⁻₃-N levels. Total carbohydrate (reducing sugars, sucrose, and fructans) concentrations in root, stem, and leaf tissue of each species were lower in plants grown at the 10 mM NO⁻₃ level than those plants grown at the 5 mM NO; level. On a whole plant basis, Kentucky bluegrass, creeping bentgrass, and annual bluegrass had 58%, 58%, and 49% lower total carbohydrate concentrations when grown at the 10 mM NO⁻₃ level. Fructose and glucose concentrations were usually, but not always lower in plants grown with 10 mM NO⁻₃-N. Comparison of the carbohydrate concentrations between treatments and tissue fractions shows sucrose levels in root tissue to have the most dramatic response to N treatment. The ratio of total carbohydrates between the low to high N treatment was lower than the ratios of either sucrose in root tissues or fructans in stem tissues, indicating total carbohydrate analysis to be a less sensitive measure of the carbohydrate concentration changes between N treatments.