Materials and methods |
| Eight tall fescue cultivars, were established
from clonal tillers and maintained in two growth chambers (22/17 oC and
15/7h day/night). NPK nutrients were added at regular intervals. After four
regrowth periods (about 42 days each), mature leaves were taken for measurement
of tensile and shear strength (Agron. J.95:414-419, 2003). After an additional 21-day regrowth to the 3 leaf-stage (10-20cm), plants were clipped and separated into leaves and pseudostems. One-half of the plant in each pot was harvested after 14 to 18 h of light exposure (400µmol m-2 sec-1). Pots containing the other half of the plant were then returned to the chamber and the lights turned off. Remaining plant material was then subjected to 8-12 h of darkness after which remaining tillers were harvested. Plant-harvesting required 10-15 minutes. Dead (dry) leaf sheaths were discarded. Plant material was placed on dry ice, maintained in freezer, later freeze dried, then ground to pass a 0.4 mm screen using a Wiley shear mill, and finally analyzed for total nonstructural carbohydrates (TNC). The TNC were assayed colorimetrically using an adaptation of Pollock’s (1982) method where samples were incubated in an acid-anthrone extractant at 85 oC for one-hour and absorbence measured at 620 nm in a SpectraMax Plus plate reader. A standard curve was prepared by simultaneously assaying known amounts of chicory inulin (Raftiline®). Data were subjected to analysis of variance. |