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ARS Home » Midwest Area » Urbana, Illinois » Global Change and Photosynthesis Research » Research » Publications at this Location » Publication #342727
Title: Chlorophyll can be reduced in crop canopies with little penalty to photosynthesis

Author
item WALKER, BERKLEY - Former ARS Employee
item DREWRY, DARREN - California Institute Of Technology
item Slattery, Rebecca
item VANLOOCKE, ANDY - Iowa State University
item CHO, YOUNG - University Of Illinois
item Ort, Donald

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2018
Publication Date: 2/1/2018
Citation: Walker, B., Drewry, D.T., Slattery, R.A., Vanloocke, A., Cho, Y.B., Ort, D.R. 2018. Chlorophyll can be reduced in crop canopies with little penalty to photosynthesis. Plant Physiology. 176(2):1215-1232.

Interpretive Summary: Global food production must increase on diminishing arable land area to provide for the dietary needs of an increasing global population with greater affluence. One proposed strategy to increase food production per unit land area is to increase the efficiency of photosynthetic conversion of light energy into biomass. Canopy-level photosynthetic conversion efficiency is currently less than half the theoretical maximum in many major food crops, providing a promising avenue for crop improvement. We took a modeling approach, using a detailed biophysical canopy model to examine the canopy-scale impacts of chlorophyll reduction. Our findings present valuable quantitative relationships between chlorophyll content, leaf optical properties and biochemistry for future efforts in optimizing canopy performance through chlorophyll reduction.

Technical Abstract: The hypothesis that reducing chlorophyll content (Chl) can increase canopy photosynthesis in soybeans was tested using an advanced model of canopy photosynthesis. The relationship between leaf Chl, leaf optical properties and photosynthetic biochemical capacity were measured in 67 soybean accessions showing large variation in leaf Chl. These relationships were integrated into a biophysical model of canopy-scale photosynthesis to simulate the photosynthetically active radiation (PAR) environment and assimilation capacity of canopies with WT, a Chl-deficient mutant (Y11y11), and Chl spanning the extremes of the 67 accessions to quantify the impact of variation in leaf-level Chl on canopy-scale photosynthetic assimilation and identify opportunities for improving canopy photosynthesis through Chl reduction. These simulations demonstrate that canopy photosynthesis should not increase with Chl reduction due to increases in leaf reflectance and non-optimal distribution of canopy nitrogen. However, similar rates of canopy photosynthesis can be maintained with a 9% savings in leaf nitrogen resulting from decreased Chl. Additionally, analysis of these simulations indicate that the inability of Chl reductions to increase photosynthesis arises primarily from the connection between Chl and leaf reflectance and secondarily from the vertical distribution of leaf nitrogen to match the PAR absorption profile. These simulations suggest future work should explore the possibility of using reduced Chl to improve canopy performance by adapting the distribution of the "saved" nitrogen within the canopy to take advantage of the more deeply penetrating PAR.