Abstract
The response of plant N relations to the combination of elevated CO2 (eCO2) and warming are poorly understood. To study this, tomato (Solanum lycopersicum) plants were grown at 400 or 700 ppm CO2 and 33/28 or 38/33 °C (day/night), and their soil was labeled with 15NO3− or 15NH4+. Plant dry mass, root N-uptake rate, root-to-shoot net N translocation, whole-plant N assimilation, and root resource availability (%C, %N, total nonstructural carbohydrates) were measured. Relative to eCO2 or warming alone, eCO2 + warming decreased growth, NO3− and NH4+-uptake rates, root-to-shoot net N translocation, and whole-plant N assimilation. Decreased N assimilation with eCO2 + warming was driven mostly by inhibition of NO3− assimilation, and was not associated with root resource limitations or damage to N-assimilatory proteins. Previously, we showed in tomato that eCO2 + warming decreases the concentration of N-uptake and -assimilatory proteins in roots, and dramatically increases leaf angle, which decreases whole-plant light capture and, hence, photosynthesis and growth. Thus, decreases in N uptake and assimilation with eCO2 + warming in tomato are likely due to reduced plant N demand.
Highlights
Anthropogenic CO2 and other greenhouse gas emissions have increased significantly since industrialization, warming the planet
DTioscduatses, imoonst previous studies have focused on single-factor manipulation approaches when Tinovedstaigtaet,inmg othset epffreectvsioofugslosbtauldeinevsirohnamveentfaol ccuhasnedgeso(ne.gs.,inCgOle2 -efnarcitcohrmemnta, nipula warming, drought, and N deposition) on plant N relations
As in our p studies [5,48], the combination of elevated CO2 (eCO2) plus chronic warming severely inhib combination of eCO2 plus chronic warming severely inhibited the growth of tomato, relative to either factor alone
Summary
Anthropogenic CO2 and other greenhouse gas emissions have increased significantly since industrialization, warming the planet. Global climate models predict atmospheric CO2 concentration will be about 420 to 935 ppm, and global mean surface temperature will increase by about 1.4 to 5.8 ◦C, by the end of this century [1,2]. This rise in temperature may cause both acute and chronic heat stress in plants, affecting both root and shoot functions [3]. CO2 enrichment alone benefits plants (e.g., increased photosynthesis and wateruse efficiency), these beneficial effects may disappear when eCO2 is compounded with other climate-change variables, such as supra-optimal temperatures [4,5,6,7]. ECO2 alone is not always beneficial to plants, as it can result in a dilution of tissue N concentration (%N) due to increased photosynthetic assimilation of C, resulting in plant tissue of lower nutritional quality for food [8,9]
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