Catalytic screens of Rubisco from differing sources in the biosphere have unveiled significant plasticity in CO2-fixing (carboxylation) potential. The extent of this variation challenges the antiquated view improving Rubisco is restricted by kinetic trade-offs in speed and CO2-selectivitiy. Indeed, new capabilities for enhancing plant Rubisco function by laboratory evolution show such catalytic trade-offs are easily surmounted and can benefit plant growth when transplanted into leaf chloroplasts. In this talk I will discuss the use of directed evolution using high throughput Escherichia coli screening to identify amino acid substitutions in differing plant Rubiscos that generate ‘better-than-nature’ step changes in performance and support visible improvements in plant growth rates.