Effect of drought and carbon dioxide on nutrient uptake and levels of nutrient-uptake proteins in roots of barley

Authors: BISTA, DEEPESH - University Of Toledo; HECKATHORN, SCOTT - University Of Toledo; JAYAWARDENA, DILEEPA - University Of Toledo; Boldt, Jennifer

Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2020
Publication Date: 10/6/2020
Publication URL: https://handle.nal.usda.gov/10113/7222882
Citation: Bista, D.R., Heckathorn, S.A., Jayawardena, D.M., Boldt, J.K. 2020. Effect of drought and carbon dioxide on nutrient uptake and levels of nutrient-uptake proteins in roots of barley. American Journal of Botany. 107(10):1401-1409. https://doi.org/10.1002/ajb2.1542.
DOI: https://doi.org/10.1002/ajb2.1542

Interpretive Summary: The atmospheric concentration of carbon dioxide (CO2) is increasing and may reach 500-900 ppm by the end of this century. At the same time, an increase in the frequency, intensity, and duration of droughts is predicted. Plants respond to water stress with decreased growth and decreased nutrient uptake. Increased CO2 typically increases plant growth but decreases tissue nutrient concentration. Therefore, elevated CO2 may partially mitigate the effects of drought on plant growth, but further decrease nutrient uptake. We investigated the effects of CO2 and drought on the concentration of nitrogen and phosphorus-uptake proteins in roots, nutrient-uptake rate, and tissue nutrient concentration in barley. Barley was grown at ambient or elevated CO2 (400 or 700ppm) and subjected to drought or well-watered conditions. Elevated CO2 did minimize the negative impact of drought on growth. However, both drought and elevated CO2 decreased % nitrogen and % phosphorus, and their effects were additive for shoot tissue. Drought, but not CO2, decreased the rates of nitrogen and phosphorus uptake in roots. In summary, elevated CO2 can help combat drought to an extent, by lessening the negative impact of drought on plant growth, but this study indicates that elevated CO2 will exacerbate the impact of drought on the nutritional quality of plant tissues. Hence, efforts to improve the tolerance of crops to changing climactic conditions should include adaptations which help plants procure more nutrients in a warmer, often drier, high-CO2 environment, which might include increasing their expression of nutrient-uptake proteins.

Technical Abstract: Due to climate change, atmospheric carbon dioxide (CO2) concentration is increasing and so is the frequency, intensity, and duration of drought. Elevated CO2 tends to negate the effect of drought by decreasing stomatal opening and, hence, water loss from leaves. Both elevated CO2 and drought typically decrease plant nutrient concentration, but their interactive effects on nutrient concentration are not well studied. We, for the first time, investigated if elevated CO2 during drought helped 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 CO2 (400 or 700ppm) and drought vs. well-watered conditions. Elevated CO2 minimized the negative impact of drought on biomass and shoot-to-root mass ratio. In contrast, both drought and elevated CO2 decreased % nitrogen (N) and % phosphorus (P) in most cases, and their effects were additive for shoot tissue. Root N- and P-uptake rates were strongly decreased by drought, but were not significantly affected by CO2. Averaged across treatments, both drought and high CO2 upregulated NRT1 (NO3- transporter) and AMT1 (NH4+ transporter) per unit total root protein, while only drought increased PHT1 (P transporter).