Phenology of northern populations of halophytic C3 and C4 grasses

Phenological analyses of halophytic grasses in Saskatchewan (52°N latitude) showed that regrowth began earlier in the C3 species, Agropyron trachycaulum (Link) Malte and Puccinellia nuttalliana (Schulte.) Hitchc. than in the C4 species, Spartina gracilis Trin. and Distichlis stricta (Torr.) Rydb. Maximum plant height was reached at about the same time in both C3 and C4 species. C3 grasses had the maximum number of green leaves per plant during spring and autumn, and C4 grasses had these during midsummer. Species on a strongly saline site (P. nuttalliana and D. stricta) began flowering earlier than those on a moderately saline site (A. trachycaulum and S. gracilis). Within each site, C3 and C4 species flowered almost simultaneously. The results indicate that at cool northern latitudes temporal niche separation in C3 and C4 grasses is most evident in vegetative characteristics. Key words: phenology, C3, C4, halophytes, temporal niche separation.

C4 grasses from the boreal forest region of northwestern Canada

Six C4 grasses (Distichlis stricta, Muhlenbergia glomerata var. cinnoides, M. mexicana, M. richardsonis, Spartina gracilis, S. pectinata) were found in grassy openings in the boreal forest of northwestern Canada. High carbon isotope ratios and Kranz anatomy confirmed that these northern populations are functionally C4 grasses. Muhlenbergia mexicana was assumed to be a C4 grass on the basis of published data. Recent collections of C4 plants tended to have more negative δ13C values than older collections from northern locations, which may reflect decreases in δ13C of atmospheric CO2 over time. In general, northern C4 species had lower δ13C values than those reported for their southern counterparts. The boreal climate in the north supports C4 species only where the mean minimum temperature for July is at least 7.5 °C. C4 grasses were found in microsites warmed by high irradiance or geothermal activity; many of the sites had saline substrates. Northern C4 populations are rare and unique in the boreal flora and deserve special protection.

Relative Tolerance of Desert Saltgrass (Distichlis stricta) and Reed Canarygrass (Phalaris arundinacea) to Boron

Desert saltgrass [Distichlis stricta(Torr.) Rydb. ♯3DISST] tolerated extremely high concentrations of boron in nutrient solution and was far more tolerant of this micro-nutrient than was reed canarygrass (Phalaris arundinaceaL. ♯ TYPAR). Boron concentrations in nutrient solution necessary to reduce growth of desert saltgrass shoots and roots by approximately 50% after 28 days of exposure were 500 and 600 ppm, respectively. In contrast, shoot and root growth of reed canarygrass was decreased approximately 50% by boron concentrations of 82 and 29 ppm, respectively. After 28 days, reed canarygrass shoots contained approximately four times as much boron as desert saltgrass shoots. Reed canarygrass has a higher transpiration rate than desert saltgrass, but this difference did not appear to cause the differential boron concentrations in the shoot tissues of the two species.