|Timothy, D - NC STATE UNIVERSITY|
Submitted to: Eastern Native Grass Symposium
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 2003
Publication Date: December 9, 2004
Citation: Fisher, D.S., Burns, J.C., Timothy, D.H. 2004. The interrelationships of productivity, forage quality, physiology, and lamina anatomy in switchgrass. Eastern Native Grass Symposium. Interpretive Summary: Native plant species can make important contributions to grazing systems and contribute to restoration of grassland ecosystems that benefit wildlife. Switchgrass is a native species of North America that has shown utility in grazing systems. In order to facilitate the use of this species new varieties are needed with increased yield and digestibility. We used a collection of 6 types of switchgrass collected from the wild to look for new methods for developing improved varieties. We found that measuring the decline in starch content of the leaves between evening and morning provided a means of simultaneously selecting grasses that both produced more forage and were higher in digestibility. This may provide and economic and labor saving method of selecting improved forage species.
Technical Abstract: Switchgrass (Panicum virgatum L.) is a native grass of North America and has proven to be a valuable species in grazing systems because of rapid summer forage growth. Switchgrass is productive with relatively digestible fiber but increased digestibility and yield are desirable for cultivar development. Previous work showed a possible association between productivity and the decrease in lamina starch content from evening to morning. Six clones were selected from a collection of wild types made in the Eastern USA to represent a wide range in digestibility and productivity. The current study tested for a correlation between overnight declines in lamina starch concentrations and productivity since this might provide a rapid means of selecting plant material for both yield and digestibility. Yield was estimated in plots 1-m wide and 10-m in length. In vitro digestibility and fiber fractions were used to estimate nutritive value. Photosynthetic rates were estimated with infrared gas analysis and lamina anatomy was described with image analysis to provide insight into the relationship of yield and nutritive value. As expected the selected plant material varied significantly for yield and digestibility but the two variables were not correlated. Estimates of photosynthesis near solar noon did not vary significantly. Spacing of vascular bundles was negatively correlated with digestibility (r = -0.74). Fluctuation in lamina starch was positively correlated with both yield (r = 0.83) and digestibility (r = 0.72). An index of percent vascular bundles was correlated with starch (r = -0.84), cell wall (r = 0.79), lignin (r = 0.95), hemicellulose (r = 0.91), and digestibility (r = -0.93). Diurnal variation in starch appears to offer a unique opportunity to select for improved plant material because of positive correlations with yield and digestibility and negative correlations with cell well, lignin, and percent vascular bundles.