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Green needlegrass [Stipa viridula Trin.] and blue grama [Bouteloua gracilis (H.B.K.) Lag.] possess the C3 and C4 photosynthetic pathways, respectively. Objectives of this study were to compare growth analysis traits of green needlegrass and blue grama and to determine the effects of 2 temperature regimes on seedling growth characteristics of both species. Seedlings of 2 accessions each of green needlegrass and blue grama were grown in growth chambers under 20 degrees C day-15 degrees C night (20-15 degrees C) and 25 degrees C day-20 degrees C night (25-20 degrees C) temperature regimes (with a 15-hr photoperiod). Beginning 2 weeks after planting, seedlings were harvested twice a week for 3 weeks. Growth analysis traits were calculated with data obtained from each harvest using exponential regression equations. Net assimilation rates of blue grama were higher than those of green needlegrass at both temperatures. Seedling growth of blue grama was more rapid at 25-20 degrees than at 20-15 degrees C, while seedling growth of green needlegrass did not differ between temperatures. Blue grama seedlings exhibited higher relative growth rates than green needlegrass seedlings at 25-20 degrees C but not at 20-15 degrees C. Green needlegrass accessions differed for relative growth rates at 25-20 degrees C, which indicated the possibility of selecting for rapid seedling growth. This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries. The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information. Migrated from OJS platform August 2020