Carbohydrate Root Reserves of Three Native Prairie Grasses

The purpose of this study was to determine the effect of natural growing conditions on carbohydrate reserves of roots, rhizomes, and crowns of big bluestem (Andropogon gerardi), little bluestem (A. scoparius), and side-oats grama (Bouteloua curtipendula). Root samples were collected monthly from August, 1959, through July, 1960. Carbohydrates determined were starch, sucrose, and reducing sugars. A photocolorimetric ferricyanide method was used for the determination of sucrose and reducing sugars. A taka-diastase method was used for estimation of starch. Rapid spring growth caused a large decrease in root reserves of the three species investigated. Total carbohydrates were lowest in May and June when growth was extensive. Replenishment of reserves occurred with a decline in growth and with flowering. Occurrence of fall growth caused a depletion of root reserves. The extent of depletion was proportional to the amount of herbage produced. Carbohydrates of side-oats grama decreased from 5.83 per cent to 3.89 per cent with the production of new herbage and flower stalks. Big bluestem displayed no visible signs of growth and the decrease in reserves was from 8.09 percent to 7.42 percent. A relatively high reserve level was maintained during the winter dormancy period. However, the initiation of spring-growth caused a marked decrease in total carbohydrates