In the North American Great Basin, seedling establishment on saline arid rangeland soils, in addition to other constraints, may be limited by high boron concentrations. In this study, germination and seedling growth of (Jose) tall wheatgrass Agropyron elongatum and (Magnar) basin wildrye Elymus cincereus were measured in relation to increasingboron concentrations in laboratory and greenhouse experiments. Both of theses grasses are more tolerant of boron than many plants.
Germination - 25 seeds of each species were placed in plastic boxes with 5g polystyrene foam and boric acid solutions of 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 150, 180, 200, 250, 300, 350, 400, 450, 500 ppm boron. A randomized experimental design was used (4 replications of each concentration); seeds were incubated in the dark at 15ºC. Germinated seedlings were counted every 2-3 days for 21 days. Radicle length of 20 randomly selected seedlings for each boron concentration and species was measured at day 21.
Seedling growth - the experiment (conducted in the greenhouse: 20-30°C; relative humidity 30-70%) comprised a randomized block design: four soil-filled pots (11.5 cm diameter x 11 cm deep) were seeded separately with 25 seeds of each species and irrigated with nutrient solution and boric acid solutions of 0, 10, 20, 40, 60, 80 and 100 ppm.After 45 days, roots and shoots were harvested, dried and weighed.
Germination - total germination of wheatgrass averaged 83% and was not reduced even at 500 ppm boron. Wildrye germination was reduced from 92 to 80% by 200 to 450 ppm boron and declined to 47% at 500 ppm. At 0 ppm, radicle growth averaged 3.3 cm for wildrye and 5.1 cm for whatgrass. Only above 100 ppm did radicle length decline (gradually with increasing boron concentration).
Seedling growth - compared with germination,growth of both species was much more sensitive to boron. Reduction in root and shoot yield of 50% occurred at boron soil concentrations of 30 and 66 ppm, respectively, for wheatgrass, and 22 and 37 ppm of boron, respectively, for wildrye.
Jose tall wheatgrass had greater absolute root growth and shoot growth was less sensitive to high boron concentrations than Magnar basin wildrye. Boron concentrations up to 97 ppm may occur in typical Great Basin saline soils of central Nevada, and would thus probably affect seedling growth and survival.