Puccinellia tenuiflora is an alkaline salt-tolerant monocot found in saline-alkali soil in China. To identify the genes which are determining the higher tolerance of P. tenuiflora compared to bicarbonate sensitive species, we examined the responses of P. tenuiflora and a related bicarbonate-sensitive Poeae plant, Poa annua, to two days of 20 mM NaHCO3 stress by RNA-seq analysis. We obtained 28 and 38 million reads for P. tenuiflora and P. annua, respectively. For each species, the reads of both unstressed and stressed samples were combined for de novo assembly of contigs. We obtained 77,329 contigs for P. tenuiflora and 115,335 contigs for P. annua. NaHCO3 stress resulted in greater than two-fold absolute expression value changes in 157 of the P. tenuiflora contigs and 1090 of P. annua contigs. Homologs of the genes involved in Fe acquisition, which are important for the survival of plants under alkaline stress, were up-regulated in P. tenuiflora and down-regulated in P. annua. The smaller number of the genes differentially regulated in P. tenuiflora suggests that the genes regulating bicarbonate tolerance are constitutively expressed in P. tenuiflora.