Author
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SINGH, SHARDENDU - University Of Maryland Eastern Shore (UMES) |
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Reddy, Vangimalla |
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Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/24/2017 Publication Date: 6/8/2017 Citation: Singh, S.K., Reddy, V. 2017. Potassium starvation limits soybean growth more than the photosynthetic processes across CO2 levels. Frontiers in Plant Science. 8:1-16. Interpretive Summary: Potassium (K) starvation and elevated carbon dioxide (CO2) have opposite effects on plant growths and their combined effects might alter plant response to the rising atmospheric CO2. To investigate this, soybean was grown under controlled environment with adequate and deficient levels of K supply under ambient and elevated CO2. Results showed that K starvation limited soybean growth traits more than the photosynthetic processes, before any visible deficiency symptom can be observed, except under severe K deficiency. The greater plant K utilization efficiency indicated the plants ability to better utilize the available tissue K concentration. The beneficial effects of elevated CO2 on the soybean photosynthesis, growth, and yield were diminished under severe K deficiency. The correlation between leaf K analysis and soybean seed yield at 29 days after planting implied its usefulness to early detect K deficiency in soybean. These results are useful to farmers and researchers to understand the interaction between K and CO2 on plant growth and underscore the importance of leaf tissue K analysis for adequate soil fertilization to minimize losses in crop yields, and to exploit the beneficial effects of high CO2 concentration. Technical Abstract: Potassium (K) deficiency might alter plant response to rising atmospheric carbon dioxide (CO2) and influence growth, and photosynthetic processes differently. To evaluate the combined effects of K and CO2 on soybean photosynthesis, growth, biomass partitioning, and yields, plants were grown under controlled environment with an adequate (control, 5.0 mM) and two deficient (0.50 and 0.02 mM) levels of K supply under ambient (aCO2, 400 ppm) and eCO2 (800 ppm) CO2. There was a significant K × CO2 interaction for several growth parameters including leaf area, biomass production, yield, and photosynthesis. Results showed that the potassium deficiency limited soybean growth traits more than the photosynthetic processes. Approximately 54% reduction in leaf K concentration under 0.5 mM versus control K treatment caused about 45% lower leaf area, biomass and yield without decreasing photosynthetic rates. Biomass decline was primarily attributed to the smaller leaf area, decreased above- and below-ground plant parts, and lower seed yield in K-deficient plants. Increased specific leaf weight, root/shoot, and decreased photochemical quenching, chlorophyll concentration and smaller plant size to reduce the nutrient demands appeared to be a few means by which the plant adjusted to the increasing potassium starvation. The increased K utilization efficiency indicated the ability of K-deficient plants to better utilize the tissue available K, except under severe K starvation. However, the tissue accumulation of N under K starvation contributed to the lower N utilization efficiency. At 29 days after planting, the correlation between the K concentration of uppermost fully expanded leaves and seed yields was the highest (r2 0.96-0.99) indicating the usefulness of leaf K analysis for early detection of K deficiency in soybean. The degree of soybean growth and yield enhancement by eCO2 relied on the level of K nutrition exhibiting more stimulation under 0.5 mM than control K treatment (e.g. 44% versus 30% yield, respectively), but it was none or negative under severe K deficiency. Thus, the eCO2 compensated, at least partially, soybean growth and seed yield depending on the K nutrition, but a severe K deficiency completely offsets the seed yield. |
