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Response of carbon assimilation and chlorophyll fluorescence to soybean leaf phosphorus across CO2: Alternative electron sink, nutrient efficiency and critical concentration

Paper ID Volume ID Publish Year Pages File Format Full-Text
30244 44465 2015 9 PDF Available
Title
Response of carbon assimilation and chlorophyll fluorescence to soybean leaf phosphorus across CO2: Alternative electron sink, nutrient efficiency and critical concentration
Abstract

•We examined response of soybean photosynthetic processes to P deficiency and CO2.•Photorespiration was the main mechanism to utilize excess energy under P deficiency.•The alternative electron sink appeared to decline in P-deficient leaves.•The P utilization efficiency of photosynthesis increased under P deficiency.•Critical leaf P concentration for photosynthetic processes was higher at elevated CO2.

To evaluate the response of CO2 assimilation rate (PN) and various chlorophyll fluorescence (CF) parameters to phosphorus (P) nutrition, soybean plants were grown in controlled environment with sufficient (0.50 mM) and deficient (0.10 and 0.01 mM) phosphate (P) supply under ambient and elevated CO2 (aCO2, 400 and eCO2, 800 μmol mol−1, respectively). Measurements were made at ambient (21%) and low (2%) O2 concentrations. Results showed strong correlation of leaf P concentration with PN and CF parameters. The P deficiency showed parallel decreases in PN, and CF parameters including quantum efficiency (Fv′/Fm′), quantum yield of photosystem II (ΦPSII), electron transport rate (JF), and photochemical quenching (qP). The Fv′/Fm′ decreased as a result of greater decline in maximal (Fm′) than minimal (Fo′) fluorescence. The eCO2 stimulated PN especially under higher leaf P concentrations. Low O2 also stimulated PN but only at aCO2. The photosynthetic carbon reduction (PCR, signified by PN) and photorespiratory carbon oxidation cycles (PCO, signified photorespiration as indicated by ratio of JF to gross PN and % increase in PN at 2% O2) was the major electron sinks. However, the presence of alternative electron sink was also evident as determined by the difference between the electron transport calculated from chlorophyll fluorescence and gas exchange measurements. Alternative electron sink declined at lower leaf P concentration suggesting its minor role in photochemical energy consumption, thus dissipation of the excess excitation pressure of PSII reaction center under P deficiency. The JF/PG and % increase in PN at 2 versus 21% O2 remained consistent across leaf P concentration suggesting PCO cycle as an important mechanism to dissipate excess excitation energy in P deficient leaves. The severe decline of Fv′/Fm′, ΦPSII, JF and qP under P deficiency also suggested the occurrences of excess radiant energy dissipation by non-photochemical quenching mechanisms. Critical leaf P concentration (CLPC) needed to achieve 90% of the maximum value was greater for PN than CF parameters. Moreover, CLPC was always higher at eCO2 suggesting increased sensitivity of soybean to P deficiency under eCO2. An increased phosphorus utilization efficiency of PN and CF parameters was also achieved but with the expense of net CO2 assimilation in P-deficient leaves.

Keywords
CF, chlorophyll fluorescence; CLPC, critical leaf phosphorus concentration; Caro, carotenoids; Chl, chlorophylls; Tchl/Caro, total chlorophyll/carotenoids ratio; Fo′, minimal fluorescence yield; Fm′, maximal fluorescence yield; Fs, steady state fluorescen
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Response of carbon assimilation and chlorophyll fluorescence to soybean leaf phosphorus across CO2: Alternative electron sink, nutrient efficiency and critical concentration
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 151, October 2015, Pages 276–284
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us