Department of Environmental Sciences, University of Toledo, OH, 43606, USA.
United States Department of Agriculture, Agricultural Research Service, Toledo, OH, 43606, USA.
Am J Bot. 2020 Oct;107(10):1401-1409. doi: 10.1002/ajb2.1542. Epub 2020 Oct 6.
Atmospheric carbon dioxide (CO ) concentration is increasing, as is the frequency and duration of drought in some regions. Elevated CO can decrease the effects of drought by further decreasing stomatal opening and, hence, water loss from leaves. Both elevated CO and drought typically decrease plant nutrient concentration, but their interactive effects on nutrient status and uptake are little studied. We investigated whether elevated CO helps negate the decrease in plant nutrient status during drought by upregulating nutrient-uptake proteins in roots.
Barley (Hordeum vulgare) was subjected to current vs. elevated CO (400 or 700 ppm) and drought vs. well-watered conditions, after which we measured biomass, tissue nitrogen (N) and phosphorus (P) concentrations (%N and P), N- and P-uptake rates, and the concentration of the major N- and P-uptake proteins in roots.
Elevated CO decreased the impact of drought on biomass. In contrast, both drought and elevated CO decreased %N and %P in most cases, and their effects were additive for shoots. Root N- and P-uptake rates were strongly decreased by drought, but were not significantly affected by CO . Averaged across treatments, both drought and high CO resulted in upregulation of NRT1 (NO transporter) and AMT1 (NH transporter) per unit total root protein, while only drought increased PHT1 (P transporter).
Elevated CO exacerbated decreases in %N and %P, and hence food quality, during drought, despite increases in the concentration of nutrient-uptake proteins in roots, indicating other limitations to nutrient uptake.
大气中的二氧化碳（CO ）浓度不断增加，一些地区的干旱频率和持续时间也在增加。升高的 CO 可以通过进一步减少气孔开度，从而减少叶片水分流失，来减轻干旱的影响。升高的 CO 和干旱通常都会降低植物的营养浓度，但它们对营养状况和吸收的相互作用研究甚少。我们研究了升高的 CO 是否通过上调根部的养分吸收蛋白来帮助抵消干旱期间植物营养状况的下降。
大麦（Hordeum vulgare）分别处于当前 CO 浓度（400 或 700 ppm）和升高 CO 浓度（400 或 700 ppm）以及干旱和充分供水条件下，然后我们测量了生物量、组织氮（N）和磷（P）浓度（%N 和 %P）、N 和 P 的吸收速率，以及根部主要 N 和 P 吸收蛋白的浓度。
升高的 CO 降低了干旱对生物量的影响。相比之下，干旱和升高的 CO 都降低了大多数情况下的%N 和%P，而且它们对地上部分的影响是累加的。干旱强烈降低了根部的 N 和 P 吸收速率，但 CO 对其没有显著影响。在各处理的平均值中，干旱和高 CO 都会导致单位总根蛋白中硝酸盐转运蛋白（NRT1）和铵转运蛋白（AMT1）的上调，而只有干旱会增加磷转运蛋白（PHT1）。
尽管根部养分吸收蛋白的浓度增加，但升高的 CO 加剧了干旱期间 %N 和 %P 的下降，从而降低了食物质量，表明养分吸收存在其他限制。
