Phosphorus nutrition affects temperature response of soybean growth and canopy photosynthesis

Authors: SINGH, SHARDENDU - University Of Washington; Reddy, Vangimalla; Fleisher, David; Timlin, Dennis

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2018
Publication Date: 8/6/2018
Citation: Singh, S., Reddy, V., Fleisher, D.H., Timlin, D.J. 2018. Phosphorus nutrition affects temperature response of soybean growth and canopy photosynthesis. Frontiers in Plant Science. 9:1116.

Interpretive Summary: Under natural growing conditions, soybean is simultaneously exposed to multiple environmental factors including temperature stress and phosphorus deficiency. However, information is lacking on the interactive effects of temperature and phosphorus nutrition on soybean. To investigate this, the seasonal growth and photosynthesis were measured in soybean grown at a range of temperature regimes under adequate and moderately deficient phosphorus fertilization. Results showed that the adverse effect of phosphorus deficiency on soybean growth was primarily observed at or below the optimum temperature. Despite the lower tissue phosphorus concentration under phosphorus deficiency, at the warmer temperatures, soybean was able to maintain the photosynthesis and dry matter production close to the values observed under the adequate phosphorus fertilization. These results are useful to researchers and farmers to understand the dynamics of phosphorus fertilization in soybean across growing temperatures and highlight the compensatory effects of warmer temperature on the soybean growth under phosphorus deficiency.

Technical Abstract: In nature, crops such as soybean are concurrently exposed to temperature (T) stress and phosphorus (P) deficiency. However, there is a lack of reports regarding soybean response to T × P interactions. To fill in this knowledge-gap, soybean was grown at four daily mean T of 22 °C, 26 °C, 30 °C, and 34 °C (moderately low, optimum, moderately high, and high temperature, respectively) each at the sufficient (0.5 mM) and deficient (0.08 mM) P nutrition for the entire season. A warmer than optimum temperature delayed the time to anthesis and pod development across P levels. The P deficiency consistently decreased plant tissue P concentration over 55% similarly across temperatures. There were significant T × P interactions for traits such as plant growth rates, total leaf area, biomass partitioning, and dry matter production, which resulted into distinct T response of soybean performance between sufficient and deficient P nutrition. Under the sufficient P level, both lower and higher than optimum T tended to decrease dry matter production and canopy photosynthesis, but under the P-deficient condition, this decrease was primarily observed at the low temperature. Additionally, growth-related traits and net canopy photosynthesis were greater at warmer versus optimum T under P deficiency. The P deficiency also increased the intrinsic P utilization efficiency of the canopy photosynthesis up to 147% across temperatures indicating better utilization of tissue P. The adverse effects of P deficiency on soybean productivity were primarily observed at or below the optimum T. However, despite the lower tissue P concentration under P deficiency, soybean was able to maintain photosynthetic carbon gain and dry matter close to the control P nutrition under the warmer temperatures. Thus, warmer than optimum T of this study appeared to compensate for the decreases in soybean canopy photosynthesis and dry matter accumulation resulting from the moderate P deficiency.