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. 2022 Jan 20;8(2):118–124. doi: 10.1038/s41477-021-01068-9

Fig. 1. Rubisco activation responses to sun–shade–sun at 30 °C.

Fig. 1

a, Rubisco activation state measured in vitro (S; individuals per accession: n = 3, IT82E-16 and V. adenantha; n = 4, IT86D-1010 and Vigna sp. Savi). b, Maximum Rubisco carboxylation rate (Vc,max) modelled from gas exchange measurements (individuals per accession: n = 4, IT86D-1010 and V. adenantha; n = 6, IT82E-16 and Vigna sp. Savi). Points show time series for individuals, lines are fixed effects predictions from nonlinear mixed-effects models that accounted for among-individual variation; in b, the model is extrapolated beyond the period 1–5 min after shade when Vc,max limited net CO2 assimilation. The response of components of Rubisco activation state are shown using equivalence plots for steady-state. c,d, Initial (Vi) (c) and total (Vt) (d) Rubisco activity in sun (850 μmol m−2 s−1, after recovery of S) and shade (150 μmol m−2 s−1, immediately preceding the end of shade). Means and s.d. are shown for individual plants (two to three technical replicates; individuals per accession: n = 3, IT82E-16 and V. adenantha; n = 4, IT86D-1010 and Vigna sp. Savi), along with a 1:1 reference (dashed line) and regression of y = ax for the means (solid line, n = 14 individuals). Vi, without pre-incubation with effectors Mg2+ and CO2, responded significantly to shade (a = 0.712, 95% CI 0.65, 0.77) and Vt did not (a = 0.967, 95% CI 0.89, 1.04). Four Vigna accessions were characterized, including two cowpea breeding lines (IT86D-1010 and IT82E-16) and two wild species (V. adenantha and Vigna sp. Savi). In both biochemistry and leaf gas exchange experiments, material was brought to steady-state photosynthesis in saturating light, then shaded for 20 min before returning in a single step to the initial light level.