Analysis of Mono- and Polysaccharides in Creeping Bentgrass Turf Using Near Infrared Reflectance Spectroscopy

Abstract

Conventional analytical methods available for measuring total non-structural carbohydrate (TNC) concentrations in turfgrasses are not suitable for nondestructive and routine in-field evaluations. The objectives of this study were to examine the utility of near infrared reflectance spectroscopy (NIRS) to analyze the concentrations of glucose, fructose, sucrose, and fructan in creeping bentgrass {Agrostis palustris Huds. [= A. stolonifera var. palustris (Huds.) Farw.]} clippings and to determine the effect of sample collection and preparation techniques on TNC content. Samples were collected from a field experiment and subjected to different post-clipping sampling techniques to determine the stability of carbohydrate components through sample processing. Instant freezing in liquid nitrogen, rapid cooling in a dry ice chamber, and ambient temperature collection techniques were examined. TNC and fructan concentrations, analyzed by NIRS, were 19 and 9% higher in samples treated with liquid nitrogen and held in dry ice followed by freeze-drying than the other sampling techniques. Calibration equations were obtained by modified partial least square (PLS) regression analysis of conventional laboratory analysis values on 97 selected NIR spectra using a scanning monochromator NIR spectrophotometer and WinISI computer software. Calibration equations were externally validated with 15 additional samples. The standard errors of calibration (SEC) were 1.3, 1.9, 1.0, 4.3, and 7.1 mg g -1 for glucose, fructose, sucrose, fructan, and TNC, respectively. Predicted and observed concentrations of all TNC components in all validation sets were highly correlated (r 2 > 0.90), except once for sucrose (r 2 = 0.59). We conclude that NIRS can analyze the TNC concentration of creeping bentgrass clippings more conveniently and faster than conventional analytical techniques. The results indicate that NIRS can determine TNC and its component concentrations in different creeping bentgrass cultivars with good accuracy.