The atmospheric CO concentration ([CO]) is increasing and predicted to reach ∼550ppm by 2050. Increasing [CO] typically stimulates crop growth and yield, but decreases concentrations of nutrients, such as nitrogen ([N]), and therefore protein, in plant tissues and grains. Such changes in grain composition are expected to have negative implications for the nutritional and economic value of grains. This study addresses two mechanisms potentially accountable for the phenomenon of elevated [CO]-induced decreases in [N]: N uptake per unit length of roots as well as inhibition of the assimilation of nitrate (NO) into protein are investigated and related to grain protein. We analysed two wheat cultivars from a similar genetic background but contrasting in agronomic features (Triticum aestivum L. cv. Scout and Yitpi). Plants were field-grown within the Australian Grains Free Air CO Enrichment (AGFACE) facility under two atmospheric [CO] (ambient, ∼400ppm, and elevated, ∼550ppm) and two water treatments (rain-fed and well-watered). Aboveground dry weight (ADW) and root length (RL, captured by a mini-rhizotron root growth monitoring system), as well as [N] and NO concentrations ([NO]) were monitored throughout the growing season and related to grain protein at harvest. RL generally increased under e[CO] and varied between water supply and cultivars. The ratio of total aboveground N (TN) taken up per RL was affected by CO treatment only later in the season and there was no significant correlation between TN/RL and grain protein concentration across cultivars and [CO] treatments. In contrast, a greater percentage of N remained as unassimilated [NO] in the tissue of e[CO] grown crops (expressed as the ratio of NO to total N) and this was significantly correlated with decreased grain protein. These findings suggest that e[CO] directly affects the nitrate assimilation capacity of wheat with direct negative implications for grain quality.

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Highlights  Wheat cultivars increased either root growth or specific root N uptake at low soil N  Wheat can utilise nitrate, ammonium, or glutamine as N source in the field  Specific root uptake capacity for ammonium was different between cultivars  Root growth but not specific root N uptake capacity was linked to greater grain N  Elevated CO2 decreased grain N of both cultivars and did not affect uptake capacities

<p class="emsd-body"><span lang="EN-GB">Seeds of ten sesame cultivars (Karaj, Darab, Safiabad, Jiroft, Borazjan, Yellow-white, Felestin, Ultan, Isfahan and Abpakhsh) were sown into soil filled pots in 2008 and 2009. Pots were watered with six levels of salts (0.0038 (tap water as control), 4.89, 8.61, 10.5, 14.54, 17.74 ds.m^-1 NaCl) until full maturity. Plant height, root and shoot dry weight, yield and yield components, seed oil and protein contents of cultivars were measured. Increasing salinity caused significant reduction in plant height, root and shoot dry weight, yield and yield components, seed oil and protein contents of all cultivars. However, there were significant differences among the cultivars for measured traits for each salinity level. Based on seed oil yield data, Safiabad and Kraj at 0.0038ds.m^-1, Safiabad and Ultan at 4.89ds.m^-1, Ultan, Safiabad and Darab at 8.61 salinity levels were the superior cultivars. High variability in tolerance to salinity among the tested sesame cultivars suggests that selection of more salt tolerant cultivars for planting or breeding purposes is possible.</span></p><p class="emsd-body"><span lang="EN-GB">Highlights</span></p><p class="emsd-body"><span lang="EN-GB">Effects of contrasting salinity levels (0.0038 (tap water as control), 4.89, 8.61, 10.5, 14.54, 17.74 ds.m^-1NaCl) on sesame cultivars were tested. Salinity reduced plant growth and yield and seed oil and protein contents. However, there were significant differences among the cultivars for measured traits for each salinity level. </span></p>

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