Which tentative proxy traits did best predict Amax response to elevated CO2?
The previously proposed proxy trait LSSR (Fabre et al., 2020), when measured under ambient CO2 level, predicted 35% (R²=0.35) of the genotypic variation of elevated-CO2effects on A max (Fig. 2A). When spikelet number, which is the sink term of LSSR, was replaced with [spikelet number * mean filled grain weight], resulting in the LSSRsinkterm, the prediction increased to 45% (Fig. 5A). The prediction increased further to 50% when the source term flag leaf area was multiplied with SPAD chlorophyll content, resulting in the term LSSRsink*SPAD (Fig. 5B).